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Nelson/Feldman Flashcards

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1
Q

What is the function of the glomerulosa layer of the adrenal gland?

A

Synthesizes aldosterone

It is the only layer that can make aldosterone.

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2
Q

What are the main products of the fasiculata and reticularis layers of the adrenal gland?

A

Steroids and androgens

They utilize the enzyme 17 alpha-hydroxylase.

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3
Q

How does cortisol interact with mineralocorticoid receptors?

A

Binds avidly but has weak mineralocorticoid activity due to conversion to cortisone

This conversion occurs in aldosterone-sensitive cells in the collecting tubules.

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4
Q

What are the consequences of glucocorticoid deficiency?

A

Stimulation of vasopressin, hyponatremia, loss of renal medullary gradient, GI signs

Can lead to polyuria (PU) and polydipsia (PD).

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5
Q

What regulates mineralocorticoid synthesis?

A

RAAS, plasma potassium, plasma sodium, ACTH

Increased potassium and angiotensin II (AT II) stimulate aldosterone production.

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6
Q

What are the primary functions of aldosterone?

A

Increases sodium resorption and potassium excretion

Affects principal cells of the distal nephron.

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7
Q

What is the result of mineralocorticoid deficiency?

A

Hyponatremia, hypochloremia, hyperkalemia, hypovolemia, azotemia

Can lead to hypotension and decreased cardiac output.

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8
Q

What is the main difference between primary and secondary hypoadrenocorticism?

A

Primary involves bilateral adrenal gland destruction; secondary involves reduced ACTH secretion

Primary requires a loss of 90% of adrenocortical function.

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9
Q

What breeds are commonly affected by hypoadrenocorticism?

A

Standard Poodle, Portuguese Water Dog, Nova Scotia Duck Tolling, Bearded Collie

Median age of onset is approximately 4 years.

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10
Q

What is a common clinical pathology finding in hypoadrenocorticism?

A

Hyponatremia and hyperkalemia

Na: K ratio less than 24 is 100% specific.

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11
Q

What does an ACTH stimulation test measure in diagnosing hypoadrenocorticism?

A

Cortisol levels at 0 hr, 30 min, and 60 min

Cortisol <2 indicates possible adrenal insufficiency.

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12
Q

What is the recommended mineralocorticoid treatment for hypoadrenocorticism?

A

DOCP (Desoxycorticosterone pivalate)

It is the only FDA approved mineralocorticoid.

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13
Q

What should you monitor after administering DOCP?

A

Electrolytes (Na and K)

Recheck at 15 and 25 days after administration.

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14
Q

What is the typical dosage of Fludrocortisone for hypoadrenocorticism?

A

0.02 mg/kg/day

Can be given as a single or divided dose.

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15
Q

What is a potential complication of treatment for hypoadrenocorticism in cats?

A

Weakness, lethargy, depression for 3-5 days post-therapy

Cats generally have a slower response to therapy.

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16
Q

What is congenital adrenal hyperplasia?

A

Mutation in enzymes needed for cortisol and aldosterone synthesis

Symptoms may include PU/PD and behavioral abnormalities.

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17
Q

What percentage of calcium is found in extracellular fluid (ECF) and what percentage is found in bone?

A

1% in ECF, 99% in bone

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18
Q

What hormone is secreted by chief cells in the parathyroid glands?

A

PTH

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19
Q

What is the function of CaSR in parathyroid glands?

A

Calcium binding leads to PTH suppression

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20
Q

What receptor does PTH act through?

A

Type 1 PTH/PTHrp receptor (PTH1R)

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21
Q

What are the actions of PTH in the kidneys?

A
  • Stimulates renal enzymes for synthesis of calcitriol
  • Increases Ca and Phos absorption from the gut
  • Stimulates bone resorption
  • Promotes reabsorption of calcium at distal tubules
  • Inhibits reabsorption of phosphorous
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22
Q

What are the clinical effects of Primary Hyperparathyroidism on the kidneys?

A

Excessive Ca can overwhelm reabsorption, leading to nephrocalcinosis and progressive renal damage

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23
Q

What hormone is produced by C cells in the thyroid?

A

Calcitonin

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24
Q

What is the primary function of calcitonin?

A

Decreases bone resorption

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25
What is the most common assay for diagnosing hypercalcemia?
Total Calcium
26
What is Humoral Hypercalcemia of Malignancy (HHM) associated with?
Secretion of PTHrp
27
What factors can contribute to osteolytic hypercalcemia?
* Multiple myeloma * Metastases of solid tumors to bone
28
What causes hypervitaminosis D?
Increased resorption from bone and absorption from the gut
29
What is the correlation between hypoadrenocorticism and hypercalcemia?
Degree of hyperkalemia correlates with hypercalcemia
30
In chronic kidney disease (CKD), what happens to total calcium levels?
Normal TCa > hyperCa > hypocalcemia
31
What is a common clinical sign of nutritional secondary hyperparathyroidism?
Pathologic fractures
32
What breeds are predominantly affected by Primary Hyperparathyroidism in dogs?
Any breed, with Keeshonden being autosomal dominant
33
What clinical signs are associated with Primary Hyperparathyroidism in dogs?
* UTI or stones * PU/PD * Lethargy * Muscle weakness * Weight loss * Renal failure
34
What are the potential effects of glucocorticoids in hypercalcemia treatment?
* Inhibit growth of neoplastic tissue * Counteract effects of vitamin D
35
What is the primary goal after surgical treatment for hyperparathyroidism?
Low to low-normal Ca at iCa of 0.9-1.2, TCa 8-9.5
36
What is the most common type of pathology found in hyperparathyroidism?
Adenoma
37
What is the recurrence rate for hyperparathyroidism if there are two masses?
Higher than if there is one mass
38
What is idiopathic hypercalcemia in cats characterized by?
50% have no clinical signs, PTH within or below reference, and decreased calcitriol
39
What treatment can help manage idiopathic hypercalcemia in cats?
* Increase dietary fiber * Use of prednisolone * Oral bisphosphonate
40
Fill in the blank: PTH is secreted by _______ in the parathyroid glands.
chief cells
41
True or False: Calcitonin has an effect on the kidneys.
False
42
What is ACTH synthesized from?
Pro-opiomelanocortin (POMC) ## Footnote POMC is a precursor that leads to the production of several peptides including ACTH.
43
List the three types of negative feedback associated with glucocorticoid secretion.
* Fast: cortisol * Intermediate: cellular exposure to glucocorticoids * Delayed: suppression of hypothalamic stimulatory peptides and pituitary ACTH
44
What are the two cell types found in the pars intermediate?
* A cells: stain for alpha-MSH > ACTH * B cells: ACTH > alpha-MSH
45
What is the role of dopamine in glucocorticoid regulation?
Dopamine exerts negative feedback on the pars intermediate, inhibiting ACTH release ## Footnote Dopamine is produced in the hypothalamus.
46
Which zone of the adrenal cortex lacks 17-alpha-hydroxylase activity?
Zona glomerulosa ## Footnote This limits its ability to produce corticosteroids and sex hormones.
47
What stimulates the secretion of cortisol from the adrenal cortex?
ACTH ## Footnote ACTH is also trophic for the zona fasciculata and reticularis.
48
What percentage of dogs with hyperadrenocorticism (HAC) have pituitary-dependent hyperadrenocorticism (PDH)?
85% ## Footnote PDH can be caused by tumors or hyperplasia in the pituitary gland.
49
What is the size difference between microadenomas and macroadenomas?
* Microadenoma: <10 mm * Macroadenoma: >10 mm
50
Name a common cause of ectopic ACTH syndrome.
Small cell carcinoma of the lung ## Footnote Ectopic ACTH syndrome often arises from neuroendocrine tumors.
51
What is food-dependent hyperadrenocorticism related to?
Enhanced adrenal responsiveness to GIP ## Footnote GIP is glucose-dependent insulinotropic peptide.
52
Which breeds are predisposed to hyperadrenocorticism?
* Poodle * Boxer * Dachshund
53
What percentage of PDH occurs in dogs weighing less than 20 kg?
75%
54
What common clinical sign is seen in 80-85% of dogs with HAC?
Polyuria/Polydipsia (PU/PD) ## Footnote The cause of PU is often unknown.
55
What is a common abdominal finding in dogs with HAC?
Hepatomegaly ## Footnote This is due to glycogen deposition in the liver.
56
What skin changes can occur due to HAC?
* Alopecia * Hyperpigmentation * Pruritus * Calcinosis cutis * Thin skin
57
What does calcinosis cutis indicate in dogs with HAC?
Dystrophic calcium deposition ## Footnote Most common locations include the dorsum, head, and inguinal area.
58
What can cause respiratory signs in dogs with HAC?
Increased abdominal pressure due to fat accumulation ## Footnote This can lead to weakened respiratory muscles and decreased lung compliance.
59
What is the typical finding in blood tests for dogs with HAC?
Stress leukogram ## Footnote This may present as mild polycythemia.
60
What is a common biochemical change associated with corticosteroids?
Increased alkaline phosphatase (ALP) ## Footnote This is often due to corticosteroid-induced changes in hepatocytes.
61
What urinary finding is common in dogs with HAC?
USG <1.020 ## Footnote This indicates dilute urine due to the effects of glucocorticoids.
62
What is a major complication associated with HAC?
Hypertension ## Footnote This is due to excess renin secretion and activation of the RAAS.
63
What is the relationship between HAC and diabetes mellitus?
Diagnosis of HAC in dogs with DM can be difficult due to false positives on screening tests.
64
True or False: Ectopic calcification is commonly found in dogs with HAC.
True
65
What is the significance of bruisability in dogs with HAC?
Cortisol-induced inhibition of collagen synthesis leads to weakened blood vessels.
66
What are common CNS signs in dogs with PDH macroadenoma?
* Dullness * Listlessness * Inappetence * Ataxia
67
What are the primary cell types found in the endocrine pancreas?
Alpha cells, Beta cells, Delta cells, Pancreatic polypeptide cells ## Footnote Alpha cells produce glucagon, Beta cells produce insulin and amylin, Delta cells produce somatostatin, and pancreatic polypeptide cells produce pancreatic polypeptide.
68
What characterizes Type 1 Diabetes Mellitus (DM)?
Permanently hypoinsulinemic, multifactorial with possible genetic basis, immune-mediated ## Footnote Histological features include reduction in number and size of pancreatic cells, decrease in beta cells, and beta cell degeneration.
69
What is a common complication associated with Type 1 DM?
Pancreatitis ## Footnote It is often seen concurrently with diabetes mellitus.
70
What is the 'honeymoon period' in diabetes?
Period within the first 6 months of diagnosis where less insulin is required ## Footnote This occurs due to residual beta cell function and correction of glucose toxicity.
71
What is the renal threshold for glucose in dogs?
200 mg/dL ## Footnote For cats, the renal threshold is 280 mg/dL.
72
What are the signs of diabetes mellitus in dogs?
Concurrent hyperglycemia and glucosuria ## Footnote Urinalysis can show trace to small ketones in relatively healthy diabetic dogs.
73
What effect does glucosuria have on urine specific gravity (USG)?
Can increase USG from 0.008 to 0.010 ## Footnote USG <1.020 with 4+ glucosuria suggests another disorder such as CKD or Cushing's.
74
What are the characteristics of NPH insulin?
Recombinant human insulin, intermediate acting, U-100 ## Footnote Contains protamine and zinc to delay insulin absorption.
75
What are insulin analogues commonly used for?
Postprandial blood glucose management ## Footnote Examples include Lispro, insulin aspart, and insulin glulisine.
76
What is the typical starting dose of insulin for dogs?
0.25 U/kg/injection ## Footnote Most dogs require about 0.5 U/kg/injection.
77
What role do oral hypoglycemics play in diabetes treatment?
Stimulate insulin secretion, inhibit glucagon secretion, enhance tissue sensitivity to insulin, or slow glucose absorption ## Footnote Most often used in type 2 diabetics and not routinely in dogs.
78
What does the Somogyi response indicate?
Physiologic response to impending hypoglycemia caused by excess insulin ## Footnote It can lead to marked hyperglycemia after a period of hypoglycemia.
79
What are insulin-binding antibodies?
Can prolong insulin action or reduce its effectiveness ## Footnote They can lead to erratic fluctuations in blood glucose.
80
What are the categories of insulin resistance?
Pre-receptor, receptor, post-receptor ## Footnote Each category involves different mechanisms affecting insulin action.
81
What is a common chronic complication of diabetes mellitus?
Cataracts ## Footnote Caused by accumulation of sorbitol and galactitol in the lens.
82
What is diabetic nephropathy characterized by?
Microvascular disease involving thickened basement membrane (glomerulosclerosis) ## Footnote Screening urine for microalbuminuria can serve as an early marker.
83
What is the recommended treatment for systemic hypertension in diabetic dogs?
Treatment if consistently over 160 mmHg ## Footnote Hypertension can result from diabetes affecting vascular compliance or glomerular function.
84
What are common clinical signs of Feline Hyperadrenocorticism?
Polyphagia, PU/PD, weight loss, abdominal distension, predisposition to bruising, curled ear tips, chronic skin infections, decreased hair regrowth, skin fragility, weakness ## Footnote PU/PD stands for polyuria/polydipsia, which refers to increased urination and thirst.
85
What is a biochemical change associated with Feline Hyperadrenocorticism?
Hypercholesterolemia (25%) ## Footnote Hypercholesterolemia refers to elevated levels of cholesterol in the blood.
86
What can chronic increase in cortisol lead to in terms of thyroid function?
Secondary hypothyroidism due to feedback on pituitary ## Footnote Thyroxine levels may be affected by prolonged cortisol elevation.
87
What is the UCCr in the context of screening tests for Feline Hyperadrenocorticism?
Sensitive screening test ## Footnote UCCr stands for Urine Cortisol to Creatinine Ratio.
88
What is the purpose of the ACTH Stim test?
Differentiate iatrogenic vs. naturally occurring Cushing's and monitor long-term treatment ## Footnote Iatrogenic Cushing's refers to excess cortisol due to external factors like medication.
89
What is the dose of ACTH for the ACTH Stim test?
125 ug/cat IM ## Footnote IM stands for intramuscular.
90
What indicates a diagnosis of Cushing's in the ACTH Stim test?
>19 post concentration ## Footnote A post concentration level of cortisol indicates the presence of Cushing's disease.
91
What does LDDST stand for?
Low Dose Dexamethasone Suppression Test ## Footnote The LDDST helps evaluate cortisol suppression in healthy individuals.
92
What is the reference range for cortisol in healthy cats during LDDST?
0.8 ug/dL ## Footnote Values above this may indicate Cushing's disease.
93
What is the significance of a cortisol level greater than 1.4 ug/dL at 8 hours in LDDST?
Consistent with diagnosis of Cushing's ## Footnote This measurement helps confirm hyperadrenocorticism.
94
What is the administration protocol for Trilostane?
High dose, low frequency: 20-30 mg/cat orally per day or Low dose, high frequency: 1 mg/kg PO q8h ## Footnote Trilostane is used to inhibit cortisol synthesis.
95
What should be done prior to starting insulin in cats treated with Trilostane?
Decrease insulin dose by 50% or to 0.1-0.5 units per kg ## Footnote This adjustment is crucial to avoid hypoglycemia.
96
What are common adverse side effects of Mitotane?
Vomiting, anorexia, lethargy ## Footnote These side effects can occur despite no change in cortisol levels.
97
What is the role of Ketoconazole in treating Feline Hyperadrenocorticism?
Inhibits 11-beta-hydroxylase and cholesterol side chain cleaving enzymes ## Footnote This action inhibits steroid synthesis.
98
What is the effect of Etomidate in cats?
Can suppress adrenocortical axis ## Footnote Etomidate is used in various species for its adrenocortical suppression effects.
99
What does Metyrapone inhibit?
11-beta-hydroxylase, converting 11-deoxycortisol to cortisol ## Footnote This drug is used to manage cortisol levels.
100
What is the significance of using Brain CT/MRI in Feline Hyperadrenocorticism?
To look for pituitary mass ## Footnote Imaging can identify structural abnormalities affecting hormone regulation.
101
What are cortisone and prednisone classified as?
Prodrugs ## Footnote They require hydroxylation in the liver by enzyme 11-beta hydroxysteroid dehydrogenase type 1.
102
Which glucocorticoid has higher anti-inflammatory effects and fewer mineralocorticoid effects compared to prednisolone?
Methylprednisolone
103
Which glucocorticoids are known for having the most potent glucocorticoid activity?
Dexamethasone and betamethasone
104
What is one method to minimize side effects of glucocorticoids?
Achieving fast metabolism by altering the D ring
105
What is the primary location of the cytoplasmic glucocorticoid receptor?
Cytoplasm
106
What happens to heat shock proteins upon glucocorticoid binding?
They dissociate, unmasks nuclear localization sequences
107
What are the two main genomic effects of glucocorticoids?
Transactivation and transrepression
108
Name two inflammatory genes that glucocorticoids suppress.
IL-1 and IL-2
109
What effect do glucocorticoids have on protein synthesis in muscle?
Catabolic effects and decreased protein synthesis
110
Fill in the blank: Glucocorticoids inhibit gene transcription of _______.
pro-opiomelanocortin
111
What is one effect of glucocorticoids on bone?
Decrease number and function of osteoblasts
112
How do glucocorticoids affect renal function?
Increase GFR and Na transport in proximal tubule
113
What cardiovascular effect do glucocorticoids have?
Increase inotrope and chronotropic effects
114
True or False: Glucocorticoids decrease capillary permeability.
True
115
What is the biological half-life of cortisol?
<12 hours
116
Which glucocorticoids are considered long-acting?
Dexamethasone and betamethasone
117
What is the primary route of administration for glucocorticoids?
Oral
118
What is a characteristic of water-soluble glucocorticoid esters?
Immediately available during emergency situations
119
What is a common adverse effect of glucocorticoid therapy in cats?
Iatrogenic hyperadrenocorticism
120
Fill in the blank: Excess glucocorticoids can lead to _______ resistance.
insulin
121
What gastrointestinal effect can glucocorticoids have?
Decreased mucosal cell turnover and impaired mucosal blood flow
122
What is the relationship between glucocorticoids and pancreatitis according to studies?
No strong association between steroids and cause of pancreatitis
123
What are the two main divisions of the pituitary gland?
Adenohypophysis and Neurohypophysis ## Footnote Adenohypophysis is the anterior pituitary, while Neurohypophysis is the posterior pituitary.
124
What are the components of the Adenohypophysis?
Pars distalis, Pars intermedia, Pars infundibularis
125
From where does the Adenohypophysis develop?
Rathke’s pouch
126
What are the five types of endocrine cells in the pituitary gland?
* Corticotrophs * Thyrotrophs * Gonadotrophs * Somatotrophs * Lactotrophs
127
Which type of endocrine cell accounts for 50% of cells in the anterior lobe?
Somatotrophs
128
What is the main hormone secreted by the pituitary gland?
Growth Hormone (GH) or somatotropin
129
How is GH secreted?
In a pulsatile fashion due to effects of GHRH
130
What inhibits GH secretion?
Somatostatin
131
What is the role of IGF-1 in relation to GH?
Works alongside GH to stimulate growth in many sites of the body
132
What are the two main IGFs?
* IGF-1 * IGF-2
133
Where is IGF-1 produced?
By the liver and many sources in the body
134
What is the function of IGFBP-3?
Binds to IGF-1 in conjunction with acid-labile subunit (ALS)
135
What is the half-life of IGF-1 when bound in ternary complexes?
Extended to 12 hours
136
What stimulates GH secretion from the pituitary gland?
GHRH released from the hypothalamus
137
What is the effect of Ghrelin?
Induces GH secretion
138
What metabolic actions are associated with GH?
* Stimulates IGF-1 * Lipolysis * Protein synthesis * Epiphyseal growth * Insulin antagonism
139
What are some non-endocrine causes of growth failure?
* Malnutrition * Organ dysfunction * Chronic disease * Parasitism
140
What is congenital hyposomatotropism?
An autosomal recessive disorder leading to severe hypoplasia of the anterior pituitary
141
What breeds are commonly affected by congenital hyposomatotropism?
* German Shepherds (GSD) * Karelian Bear dog * Saarloos Wolfdog * Czechoslovakian Wolfdog
142
What are clinical manifestations of congenital hyposomatotropism?
* Growth retardation * Pointed muzzle * Delayed growth plate closure * Soft and wooly hair coat * Hyperpigmentation and skin issues
143
What is the recommended diagnostic workup for congenital hyposomatotropism?
* Thyroid panel * TLI * AUS * Echo
144
What is the treatment for congenital hyposomatotropism?
Recombinant human growth hormone (rhGH) and progestins
145
What is the prognosis for untreated congenital hyposomatotropism?
Usually die at ages 3-5 years
146
What is acquired hyposomatotropism?
Caused by neoplastic, traumatic, vascular, inflammatory, and infectious disorders of the pituitary
147
What breeds are associated with Alopecia X?
* Pomeranian * Alaskan malamute * Chow Chow * Keeshond
148
What are common clinical signs of hypersomatotropism (acromegaly) in cats?
* PU/PD * Polyphagia * Weight loss * Neurologic signs
149
What is the most common cause of acromegaly in cats?
Pituitary adenoma
150
What are the imaging techniques used for diagnosing acromegaly?
* Ultrasound * CT/MRI
151
What is the treatment goal for acromegaly in cats?
Manage acromegaly and diabetes mellitus (DM)
152
What type of adenoma is associated with hypersomatotropism in dogs?
Acidophilic adenoma
153
What are clinical manifestations of hypersomatotropism in dogs?
* Inspiratory stridor * Exercise intolerance * Enlarged tongue * Prognathia inferior * Weight gain
154
What is the significance of IGF-2 measurement in dogs?
Helps in the hormonal evaluation of acromegaly
155
What is the expected GH concentration response in an IV Glucose Tolerance Test (IVGTT) for dogs with acromegaly?
GH concentration should show no change in levels
156
What is the range of growth hormone (GH) measurements recommended for evaluation?
3 to 5 measurements every 10 min
157
What does a somatostatin suppression test indicate if GH does not suppress?
Indicates acromegaly
158
What is the purpose of the IV Glucose Tolerance Test (IVGTT) in relation to GH?
Measurement of GH in dogs with normal BG or mild hyperglycemia
159
What should GH concentration levels indicate if acromegaly is present during an IVGTT?
No change in levels
160
What hormone levels are measured to evaluate acromegaly?
GH and IGF-2
161
What are the expected results of thyroid testing in acromegaly?
T4 and TSH normal
162
What is the expected GH and IGF-1 levels in primary hypothyroidism?
Increased
163
What is the definitive diagnosis for acromegaly?
Lack of GH suppression or increased IGF-1
164
What is the top differential diagnosis (ddx) for acromegaly?
Hypothyroidism
165
What treatment is suggested for diestrus-associated acromegaly?
OVH (ovariohysterectomy)
166
What are the treatment options for acromegaly?
* Removal of mammary tumors * Treatment of pituitary tumor
167
What is the prognosis for diabetic dogs with acromegaly?
Difficult to predict
168
Can some dogs with acromegaly go into remission?
Yes, but it depends on the degree of beta-cell damage
169
What is a major risk factor for feline hyperthyroidism related to diet?
Canned food due to nutritional deficiency/excess or goitrogens ## Footnote Goitrogens are substances that disrupt thyroid function, including certain plastics and flame retardants.
170
What deficiency can lead to hypothyroidism in cats?
Iodine deficiency ## Footnote Iodine deficiency can cause elevated TSH and goiter formation.
171
Which substance can inhibit thyroid hormone activity?
Soy isoflavones ## Footnote Soy can inhibit thyroid peroxidase and reduce T4 to T3 conversion.
172
What is the #1 clinical sign of feline hyperthyroidism?
Weight loss
173
List three clinical features of feline hyperthyroidism.
* Polyphagia * Nervousness, hyperactivity, aggressive behavior * PU/PD
174
What does PU/PD stand for in the context of feline hyperthyroidism?
Polyuria/Polydipsia
175
What is a common gastrointestinal dysfunction seen in cats with hyperthyroidism?
Vomiting ## Footnote Vomiting occurs in about 50% of hyperthyroid cats.
176
What is the significance of a palpable cervical mass in cats?
It indicates a goiter.
177
True or False: Cats with hyperthyroidism often exhibit tachycardia.
True
178
What is a thyroid storm?
Increased cellular response to thyroid hormones with superimposed insults.
179
What does CBC stand for in the context of diagnostic evaluation?
Complete Blood Count
180
What laboratory finding is associated with elevated thyroid hormone levels?
Erythrocytosis ## Footnote Thyroid hormones stimulate erythropoietin production, leading to increased red blood cell counts.
181
What imaging technique helps assess thyroid function and location?
Thyroid scintigraphy
182
What are the choices of radionuclide used in thyroid scintigraphy?
* I-131 * I-123 * Pertechnetate (99 mTcO4)
183
What is the gold standard for measuring free thyroxine concentration in research?
Equilibrium dialysis
184
Fill in the blank: The administration of T3 in a normal cat results in _______ suppression of TSH and T4.
TSH and T4
185
What is the common starting dose of Methimazole for treating feline hyperthyroidism?
1.25-2.5 mg PO q12-24h
186
What is the mechanism of action for anti-thyroid drugs in hyperthyroid cats?
Inhibit oxidation of iodide and coupling of iodothyronines.
187
What is the main concern with using Propylthiouracil (PTU) in cats?
Unacceptable rates of adverse effects
188
What percentage of cats typically become euthyroid after treatment with I-131?
93%
189
What is the treatment of choice for feline thyroid carcinoma?
Thyroidectomy
190
True or False: Nutritional management for hyperthyroid cats involves iodine restriction.
True
191
What is a potential side effect of using beta-blockers like Propranolol in hyperthyroid cats?
Bronchospasm
192
What does the term 'euthyroid' refer to?
A state where thyroid hormone levels are normal.
193
What is the functional unit of the thyroid gland?
Follicle
194
What is the role of the sodium-iodine symporter (NIS) in thyroid hormone synthesis?
Brings iodide into the follicle
195
Which enzyme oxidizes iodine in the thyroid gland?
Thyroid peroxidase (TPO)
196
What are the two primary thyroid hormones produced?
* T4 * T3
197
What regulates the secretion of T4 and T3?
TSH (thyrotropin)
198
True or False: T3 levels inhibit TSH secretion.
True
199
What is the Wolff-Chaikoff block?
Decrease in thyroglobulin iodination and thyroid hormone synthesis
200
What is the major product of the thyroid gland?
T4
201
Which protein is T4 highly bound to in plasma?
* Thyroxine-binding globulin (TBG) * Thyroxine-binding prealbumin (TBPA) * Albumin * Plasma lipoproteins
202
Which thyroid hormone enters cells more rapidly and is more potent?
T3
203
What physiological functions do thyroid hormones promote?
* Fetal development * Calorigenesis
204
What are the three classifications of hypothyroidism?
* Primary * Secondary * Tertiary
205
What is lymphocytic thyroiditis?
Infiltration of lymphocytes, plasma cells, and macrophages in the thyroid
206
What is idiopathic atrophy in the context of hypothyroidism?
Progressive reduction in size of thyroid follicles and replacement with adipose
207
What is the most common neoplasia causing secondary hypothyroidism?
Functional corticotrophic tumor causing PDH
208
What does a diagnosis of congenital hypothyroidism indicate?
Defect anywhere in hypothalamic pituitary thyroid axis
209
What are common clinical signs of adult hypothyroidism?
* Decreased metabolic rate * Dermatologic issues * Neurologic signs * Myxedema coma
210
What is the hallmark of congenital hypothyroidism?
Retardation of growth and mental development
211
What type of anemia is associated with hypothyroidism?
Normocytic normochromic nonregenerative anemia
212
What is the gold standard for thyroid function testing?
Serum fT4 by MED
213
What is the initial treatment for hypothyroidism in dogs?
Levothyroxine
214
What should be monitored after starting treatment for hypothyroidism?
* Serum T4 or fT4 * TSH
215
What effect does glucocorticoids have on thyroid function tests?
Decreases TSH
216
True or False: T4 and T3 levels increase in diestrus females compared to anestrus.
True
217
What should be done if clinical signs of hypothyroidism do not resolve?
Increase dose of levothyroxine
218
What does the term 'nonthyroidal illness syndrome' refer to?
Suppression in thyroid hormone due to concurrent illness
219
What is the purpose of the TSH stimulation test?
Differentiate hypothyroid from euthyroid
220
What is the significance of serum thyroglobulin autoantibodies?
Present in 50% of lymphocytic thyroiditis cases
221
What breeds are commonly affected by primary hypothyroidism?
Rat Terrier (TPO deficiency)
222
What are the clinical signs of myxedema coma?
* Profound weakness * Hypothermia * Bradycardia * Diminished consciousness
223
What do increased target cells in a CBC indicate?
Increased erythrocyte membrane cholesterol loading
224
What is the recommended initial dose of levothyroxine for dogs?
0.02 mg/kg of body weight
225
What should be measured if TSH is indicated?
TSH should be measured
226
What is the recommended action if TSH is within reference?
No adjustment needed
227
What should be kept in mind if the measurement time is >4-6 hours?
Not looking at peak dose
228
What action is recommended if thyroid levels are above reference and >6.0 ug/dL?
Recommend reduction
229
Can TSH be used to distinguish adequately and over-supplemented?
No
230
What are some causes of treatment failure in hypothyroidism?
* Hypothyroidism mistook for Cushing’s * Owner compliance * Medication preparation * Inappropriate dose or frequency * Poor intestinal absorption
231
What should be substituted if poor intestinal absorption is suspected?
Substitute T3 for T4
232
What is Liothyronine Sodium indicated for?
When levothyroxine failed
233
What is the dose for Liothyronine Sodium?
4-6 ug/kg q8h
234
What should be monitored after administering Liothyronine Sodium?
Evaluate T3 2-4 hours after administration
235
What is the risk associated with Liothyronine Sodium?
Higher risk of thyrotoxicosis
236
What is the typical ratio in Combo Thyroxine/Triiodothyronine products?
4:1 of T4:T3
237
What are some risks associated with thyroid extracts?
* Risk of allergy * Batch variability * Shelf life
238
What is the treatment for Myxedema Coma?
Injectable T4 at 4-5 ug/kg every 12 hours or oral
239
What are signs of thyrotoxicosis?
* Panting * Nervousness * Anxiety * Tachycardia * Aggression * PU/PD * Polyphagia * Weight loss * Sinus tach * A. fib * Syncope
240
What is the prognosis for puppies with hypothyroidism?
Guarded
241
What is a common etiology of feline hypothyroidism?
Iatrogenic causes such as thyroidectomy, radioactive iodine, anti-thyroid drugs
242
What percentage of cats develop hypothyroidism after I-131 treatment?
30%
243
What are common clinical signs of adult-onset feline hypothyroidism?
* Lethargy * Inappetence * Dermatologic issues * Obesity
244
What are some clinical signs of congenital feline hypothyroidism?
* Evident at 6-8 weeks * Disproportionate dwarfism * Mental dullness * Constipation * Bradycardia * Hypothermia * Prolonged retention of deciduous teeth
245
What is the baseline serum T4 test used for?
Could indicate either hypoT4 or euthyroid
246
What is the utility of baseline T3 in testing?
Not very useful
247
What is the advantage of testing fT4?
Less influenced by non-thyroidal illness than T4
248
What does an elevated TSH indicate?
Great specificity
249
What is the protocol for the TSH stimulation test?
25 mcg IV
250
What should T4 levels do in a euthyroid response after TSH stimulation?
Increase 2-3x 6-8 hours later
251
What is the expected T4 increase in the TRH stimulation test?
1-2 ug/dL or greater than 50% above baseline
252
What is the typical treatment dosage for feline hypothyroidism?
0.05-0.1 mg/day
253
How long should one wait before assessing the response to treatment in feline hypothyroidism?
6 weeks
254
What is the treatment goal for T4 levels in feline hypothyroidism?
1.0-3.0 ug/dL
255
What problems often persist in congenital cases of feline hypothyroidism?
Neurologic and musculoskeletal problems
256
What is the efficacy comparison of Mitotane for PDH and ADH?
PDH > ADH
257
How should Mitotane be objectively monitored?
Via ACTH stim
258
What percentage of cases can Mitotane cause complete adrenocortical insufficiency?
6-10%
259
What pre-induction factors should clients monitor?
* Attitude * Activity * Daily water intake * Appetite
260
What is a contraindication for Mitotane treatment?
Decreased appetite
261
How should Mitotane be administered?
Give with food
262
What is the pill size of Mitotane that may necessitate one dose in a small dog?
500 mg
263
What is the induction dosage of Mitotane for PDH?
40-50 mg/kg/day divided BID
264
What are some signs of appetite decrease during Mitotane induction?
* Eating slower than usual * Vomiting or diarrhea * Listlessness * Water intake <60 ml/kg/day
265
What is the maximum duration of Mitotane induction?
8 days
266
What is the goal for pre- and post-ACTH concentration during Mitotane therapy?
1-5 ug/dL
267
What should be done if ACTH concentration is above the desired range during Mitotane therapy?
Continue for another 3-7 days
268
What are potential reasons for no improvement after 21 days of Mitotane treatment?
* More resistant AT * Inherent resistance to mitotane * Too low induction dose * Incorrect diagnosis * Drug potency issues * Another drug interference (e.g., phenobarbital)
269
What is the maintenance dose of Mitotane?
50 mg/kg/week
270
How often should ACTH stimulation tests be performed after initiating Mitotane?
1, 3, and 6 months after initiating, then q3months
271
What percentage of dogs with PDH relapse within one month?
60%
272
What is the post-ACTH concentration range for increasing Mitotane dose?
5-9 ug/dL (moderately elevated)
273
What should be done if post-ACTH concentration is greater than 9 ug/dL?
Restart induction
274
What percentage of dogs with PDH experience decreased aldosterone concentration?
79%
275
What should be administered during major stress while on Mitotane?
Prednisone 0.2 mg/kg/day
276
What is the protocol for planned medical adrenalectomy with PDH?
* Administer Mitotane for 24 days (50-75 mg/kg/day up to 100 mg/kg/day) in 3-4 portions with food * Start pred at high dose (1 mg/kg/day) * Administer fludrocortisone (0.0125 mg/kg/day) and sodium chloride (0.1 mg/kg/day) * Weekly owner reports * Recheck electrolytes and ACTH stim after 1 week
277
What is the induction dosage for ADH using the ablative protocol?
50-75 mg/kg/day
278
What should be administered concurrently during the induction of ADH?
Physiologic doses of prednisone
279
How often should ACTH stimulation be repeated during ADH induction?
Every 10-14 days
280
What is the maintenance dose for ADH once pre and post are within reference?
75-100 mg/kg/week
281
What is the induction dosage for ADH using the non-ablative protocol?
50 mg/kg/day divided BID
282
How long should ACTH stim be rechecked after non-ablative protocol induction?
7-10 days later
283
What should be done if there is no improvement after non-ablative protocol induction?
Increase to 75-100 mg/kg/day for another 7-10 days
284
What are chromaffin cells?
Modified postganglionic sympathetic neurons lacking axons ## Footnote Chromaffin cells are located in the adrenal medulla and secrete hormones into the bloodstream.
285
What hormones are synthesized by chromaffin cells?
Norepinephrine and epinephrine ## Footnote These hormones are also known as catecholamines.
286
What enzyme does cortisol induce for catecholamine synthesis?
PNMT (phenylethanolamine N-methyltransferase) ## Footnote PNMT is responsible for the conversion of norepinephrine to epinephrine.
287
What is the percentage of pheochromocytomas that have local invasion?
34% ## Footnote This indicates the aggressiveness of certain tumors.
288
What are catecholamines?
Epinephrine, norepinephrine, dopamine ## Footnote They are synthesized from the amino acid tyrosine.
289
What is the metabolic pathway for catecholamines starting from tyrosine?
Tyrosine 🡪 L-DOPA 🡪 dopamine 🡪 norepinephrine 🡪 epinephrine ## Footnote This pathway is essential for catecholamine synthesis.
290
How are catecholamines metabolized?
Metabolized to metanephrine via COMT and MAO ## Footnote COMT stands for catechol-O-methyltransferase, and MAO stands for monoamine oxidase.
291
What is the short half-life of catecholamines?
1-3 minutes ## Footnote This short duration affects their physiological effects.
292
Which receptors do catecholamines act on?
Alpha and beta receptors ## Footnote These receptors mediate various physiological responses.
293
What effect does epinephrine have on blood pressure?
Depends on concentration ## Footnote Different concentrations of epinephrine can lead to vasoconstriction or vasodilation.
294
What are the clinical manifestations of pheochromocytoma?
Paroxysmal episodes, lethargy, PU/PD, seizures, tachypnea, dyspnea, acute blindness, anorexia, weight loss, abdominal pain, V/D ## Footnote PU/PD stands for polyuria and polydipsia.
295
What is a common laboratory finding in pheochromocytoma?
Hypercholesterolemia ## Footnote This condition can result from catecholamine-induced lipolysis.
296
What is the most sensitive test for detecting metanephrines?
24-hour urine samples for metanephrine ## Footnote This test is preferred for its sensitivity.
297
What medication is used to block catecholamines before surgery?
Phenoxybenzamine ## Footnote It is a non-competitive alpha-adrenoreceptor blocker.
298
What is the role of metyrosine in medical treatment?
Tyrosine hydroxylase inhibitor ## Footnote It prevents further catecholamine synthesis.
299
What are paragangliomas?
Neuroendocrine tumors that develop from primitive neural crest cells ## Footnote They are extra-adrenal and can occur in various locations.
300
What should be ruled out when encountering an incidental adrenal mass?
Adrenal metastasis and hormonally active tumors ## Footnote It is crucial to identify the nature of the mass for proper management.
301
What are the three major components of MEN-1?
Parathyroid tumors, pancreatic tumors, pituitary tumors ## Footnote Diagnosing MEN-1 requires the presence of at least two of these components.
302
What characterizes MEN-2?
Pheochromocytoma, primary hyperparathyroidism, medullary thyroid carcinoma ## Footnote MEN-2 is associated with significant morbidity and mortality.
303
What structures are involved in the control of water metabolism?
Hypothalamus, pituitary, thirst center, kidney, plasma osmolality, fluid in vascular compartment ## Footnote These structures work together to regulate water intake and urine volume.
304
What is water balance?
Regulation of water intake (thirst center) + urine volume (vasopressin) ## Footnote Water balance is crucial for maintaining homeostasis in the body.
305
What regulates vasopressin release?
Blood pressure (RAAS), osmolality (vasopressin) ## Footnote Increased osmolality slightly raises vasopressin levels.
306
What are magnocellular neurons responsible for?
Synthesize oxytocin and vasopressin ## Footnote These neurons are located within the hypothalamic nuclei.
307
What inhibits the release of vasopressin under normal conditions?
Arterial baroreceptors ## Footnote These baroreceptors provide a tonic inhibition of vasopressin release.
308
What is the primary effect of ADH?
Conserve body fluid by reduction in urine volume ## Footnote This effect requires the presence of ADH, V2 receptors, and a medullary concentrating gradient.
309
What stimulates thirst?
Increase in ECF osmolality, decrease in IV volume ## Footnote Osmoreceptors in the anterior hypothalamus are involved in this regulation.
310
What are the broad categories for PU/PD differentials?
Primary polydipsic, primary polyuric ## Footnote Primary polyuric includes central DI, nephrogenic DI, osmotic-diuresis, and interference with ADH secretion.
311
What causes osmotic diuresis?
Diabetes mellitus, primary renal glycosuria, chronic renal failure, post-obstructive diuresis ## Footnote These conditions lead to increased urine output due to osmotic effects.
312
What is primary nephrogenic DI?
Congenital defect involving cellular mechanisms for opening water channels ## Footnote This results in impaired kidney response to vasopressin.
313
What can lead to acquired secondary nephrogenic DI?
Interference between ADH and ADH receptors, bacterial endotoxins, hypercalcemia, hepatic insufficiency, Cushing’s disease ## Footnote These factors can disrupt normal kidney function and response to ADH.
314
What is the typical USG range for renal insufficiency?
1.008-1.015 ## Footnote This range is suggestive of renal insufficiency.
315
What does a USG >1.030 indicate?
Normal urine concentrating ability ## Footnote This supports the diagnosis of conditions like central DI or primary nephrogenic DI.
316
What is the significance of plasma vasopressin concentrations?
CDI: below normal; primary NDI or psychogenic PD: normal or increased AVP ## Footnote This helps differentiate between types of diabetes insipidus.
317
What is the role of DDAVP in treatment?
Vasopressin analogue with minimal vasopressor activity ## Footnote It is used to manage conditions like central DI.
318
What is the function of thiazide diuretics in DI treatment?
Helpful with NDI and partial CDI by reducing urine volume ## Footnote They paradoxically promote Na and water reabsorption at the proximal tubule.
319
What does a modified water deprivation test (MWDT) assess?
AVP secretory capabilities and renal responsiveness to AVP ## Footnote It helps in diagnosing the type of diabetes insipidus.
320
What indicates a positive response to DDAVP?
USG increased by 50% or >1.030 ## Footnote This suggests partial central diabetes insipidus.
321
What is the expected response in primary nephrogenic DI during MWDT?
Urine concentration barely changes; urine osmolality <300 mOsm/kg ## Footnote Minimal to no change in urine osmality and USG with AVP administration.
322
What are the complications associated with MWDT?
Hypertonic dehydration, hypernatremia ## Footnote These complications can arise from excessive water loss.
323
What imaging techniques are useful for diagnosing idiopathic CDI?
MRI and CT ## Footnote They help rule out neoplasia and other structural abnormalities.
324
What is the effective dosage range for P in partial CDI?
10-40 mg/kg/day ## Footnote Effective dosages not established but reported range is noted.
325
What adverse effect is associated with P due to induced insulin secretion?
Hypoglycemia ## Footnote This occurs as a result of the drug's action.
326
What is the role of thiazide diuretics in treating NDI and partial CDI?
Helps reduce urine volume ## Footnote Thiazide diuretics paradoxically inhibit Na reabsorption at the ascending limb of the loop of Henle.
327
What is the typical dosage for thiazide diuretics?
20-40 mg/kg/day ## Footnote Should be used with a low Na diet and Na monitoring.
328
What is the recommended management for CDI or primary NDI?
Na restriction ## Footnote This is a key part of managing these conditions.
329
What is the recommended approach when no treatment is available for CDI or primary NDI?
Allow free water access ## Footnote This is essential for maintaining hydration.
330
What behavior modification can be applied for psychogenic PD?
Gradually limit water intake ## Footnote This should be done in a high normal range and may involve changing the environment.
331
What does SIADH stand for?
Syndrome of Inappropriate Antidiuretic Hormone secretion ## Footnote It is characterized by excess ADH without osmotic stimuli.
332
Name one condition associated with SIADH.
Tumors ## Footnote Examples include carcinomas, lymphoma, and thymoma.
333
What are the diagnostic criteria for SIADH?
Hyponatremia, euvolemia, plasma osmolality <275, urine osmolality greater than plasma osmolality, increased Na excretion, normal renal function ## Footnote R/O other causes of hyponatremia is also necessary.
334
What is a potential complication of correcting hyponatremia too quickly?
Osmotic demyelination syndrome ## Footnote This condition involves demyelination of white matter.
335
What is the treatment goal for correcting hyponatremia in SIADH?
Increase Na to greater than 125 mEq/L ## Footnote This is typically done with 0.9% saline or hypertonic saline.
336
What defines hypodipsic hypernatremia?
Diminished sensation of thirst and diminished release of AVP ## Footnote Characterized by chronic hypernatremia with euvolemia and normal renal function.
337
What clinical findings are associated with hypodipsic hypernatremia?
Na 168-215, USG >1.030, dehydration, azotemia ## Footnote These findings indicate a high Na level and dilute urine.
338
What is the main mechanism of action (MOA) in hypodipsic hypernatremia?
Defect in thirst center and osmoreceptors ## Footnote This leads to impaired thirst perception.
339
What is one treatment option for hypodipsic hypernatremia?
Increase water intake ## Footnote This can be done through food, tube feeding, or using chloropropamide.

Ettingers (11 decks)

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