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.pharmocology > Thyroid and Parathyroid > Flashcards

Thyroid and Parathyroid Flashcards

1
Q

Hypothalamic- Pituitary- Thyroid Axis

A

Hypothalamus: TRH
Pituitary: TSH
Thyroid: T4, T3 (with negative feedback ^^)

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2
Q

Thyroid Hormone

A

Thyroglobin synthesized by smooth endoplasmic reticulum
Ingested iodine converted to iodine in GI tract

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3
Q

Iodine

A

Daily requirement (higher in cats)
Thyroid hormones only iodinated organic compounds in the body

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4
Q

Hypothyroidism

A

In dogs and horses
CS: Lethargy, mental depression, weakness, non pruritic hair loss

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5
Q

Primary hypothyroidism

A

99% spontaneous disease
Cells lost due to idiopathic atrophy or lymphatic thyroiditis

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6
Q

Secondary hypothyroidism

A

Deficiency in TSH
Congenital pituitary malformation

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7
Q

Levothyroxine

A

Hypothyroidism tx
T4 supplementation (treats symptoms)
Start slow, then ↑
Efficacy 1-3 months of dosing

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8
Q

Therapeutic failure of Levothyroxine

A

Improper dose of frequency
Owners compliance
Problems with absorption, metabolism, or excretion
Outdated
Incorrect dx

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9
Q

Hyperthyroidism

A

Most common in geriatric cats
CS: Thyrotoxicosis (excess T4 and T3), WL, ravenous appetite, hyperactivity, PU/PD

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10
Q

Cardiac CS of Hyperthyroidism

A

Tachycardia, PVC, Gallop rhythms

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11
Q

Hyperthyroidism tx

A

Definitive therapy (thyroidectomy, radioactive iodine)
Medical management (methimazole)

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12
Q

I 131 (iodine therapy)

A

A cure given SQ*, PO, IV
Euthyroidism occurs 1-3 weeks of admin
Tx in cats (ectopic thyroid tumors)

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13
Q

MOA of I131

A

Actively taken up and concentrated by thyroid tissue
Beta particles target abnormal tissues

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14
Q

Disadvantage of I131 therapy

A

Available in specialty referral centers
Radiation safety precautions must be taken
Safe to go home in 4 days
Retreatment may be necessary

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15
Q

Advantages of I131

A

Least invasive
No toxicity
Survival time 25 months

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16
Q

Methimazole

A

Reverse thyrotoxicosis and maintains euthyroidism
T4 concentrations in the lower half of reference range

17
Q

MOA of METHIMAZOLE

A

Blocks synthesis of thyroid hormones by preventing iodine and peroxidase from their normal interactions with thyroglobulin to form T3 and T4 (not secreted)

18
Q

Methimazole characteristics

A

Does not affect tumor size
CS will recur with discontinuation
Used before sx to stabilize patient

19
Q

Side effects of methimazole

A

Serum antinuclear abs
No CS
Disappears after drug discontinued

20
Q

Thyroid and drug interactions

A

Glucocorticoids
Anticonvulsants
NSAIDs (salicylates and phenybutazone)
Antimicrobials (trimethoprim/ sulfa)
Radiocontrast agents

21
Q

Parathyroid

A

Normal calcium homeostasis
Hypoparathyroid= hypocalcemia
Hyperparathyroid= hypercalcemia

22
Q

Normal calcium homeostasis

A

Reabsorption of calcium and phosphorus in bone and distal renal tubular cells
Vit. D mediated absorption of calcium from intestinal tract

23
Q

Hypocalcemia

A

↑ PTH → ↑ Ca resorption from urine → ↑ Ca and Phosphorus mobilization from bone → ↑ Vit. D synthesis

24
Q

Hypoparathyroidism in dogs

A

Destruction of parathyroid glands by disease, trauma or sx removal

25
Q

Hypoparathyroidism in cats

A

Injury or removal of parathyroid gland during thyroidectomy

26
Q

CS of Hypoparathyroidism

A

Peripheral tetany (cramping, lameness)
Muscle fasciculation
Stiff gait

27
Q

T/F: No tx compensates for lack of PTH

A

TRUE

28
Q

Calcium supplementation

A

For Hypoparathyroidism
IV prep: chloride, gluconate (potential for cardiac toxicity
Oral: carbonate, lactate, gluconate

29
Q

Calcitriol

A

For hypoparathyroidism
Vit. D supplement facilitates Ca absorption

30
Q

Hypercalcemia in dogs

A

Malignancy: Lymphosarcoma, multiple myeloma and anal sac adenocarcinoma

31
Q

Hypercalcemia in cas

A

Idiopathic hypercalcemia, neoplasia and renal failure

32
Q

Hypercalcemia tx (supportive)

A

Address underlying disorder
IV fluid therapy (correct dehydration and ↓ GFR)

33
Q

Hypercalcemia tx (medication)

A

Furosemide (↑ calcium excretion)
Glucocorticoids (↓ intestinal and bone calcium absorption and ↑ renal calcium excretion)
Sodium bicarbonate (Crisis only, ↓ ionized calcium)

34
Q

Hyperparathyroidism pathophysiology

A

↑ PTH secretion from hyperplastic or parathyroid gland carcinomas
Uncommon in dogs and cats
Older animals

35
Q

Hyperparathyroidism tx

A

Ablation of abnormal parathyroid tissue (sx)
Address secondary hypercalcemia

.pharmocology (21 decks)

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