Parathyroid Disorders Flashcards by Courtney Smith

Calcium homeostasis

Ionized Calcium

this is the physiologically active fraction and ionized calcium is maintained within a fairly narrow range.

This fraction 44-50% of total calcium in the normal patient

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Calcium Homeostasis

Bound Calcium

typically bound to albumin in serum

Inactive form of calcium

50-55% of total calcium in the normal patient

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Calcium Homeostasis

Complexed calcium

accounts for less than 1-2% of total calcium.

In chronic renal failure, retention of sunstances such as citrate and oxalate tht form calcium complexes elevate the total calcium without affecting ionized calcium

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parathyroid Hormone

principle hormone that affects IONIZED CALCIUM

secreted by the parathryoid glands, which are in proximity to the thyroid gland.

Dogs and Cats have 4 parathyroid glands.

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Parathyroid Hormone Effects

decreases renal calcium excretion

Increases renal phosphorous excretion

Increases calcium and phosphorous mobilization from bone

Stimulates production of 1.25-dihydroxycholecalciferol (VitD). increases bone calcium and phosphorous via enhanced intestinal uptake and bone mobilization

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Primary Hyperparathyroidism

occurs in both dogs and cats

in dogs, among the common causes of sever hypercalcemia.

In cats, primary hyperparathyroidism is uncommon

In both species, primary hyperparathyroidism is typically caused by a single parathyroid adenoma

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Priamry Hyperparathyroidism

Diagnosis

confrimed by documenting elevated serum PTH and ionized calcium

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Hyperparathyroidism is characterized by

HYPERCALCEMIA

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Clinical signs of Hypercalcemia

often mild or absent

GI: common - anorexia, vomiting, constipation; Less common - Pancreatitis

Renal: PU/PD, possible stranguria/pollakiuria form stone formation

CNS: mental dullness, obtundation, coma, shivering, twitching, seizures

Muscle: Weakness

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Calcitonin

Hormone released by the thyroid gland that reduces blood calcium levels

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Differential diagnosis: Hyperparathyroidism

Hypercalcemia of malignancy

MOST COMMON cause in dogs

Tumors commonly associated with hypercalcemia include: Lymphosarcoma, Multiple Myeloma, Apocrine gland Carcinoma, leukemias, mammary gland carcinoma, thymoma,

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Differential diagnosis: Hyperparathyroidism

Hypercalcemia of malignancy

Diagnosis

dependent on appropriate imaging/FNA/Biopsy procedures

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Differential diagnosis: Hyperparathyroidism

Idiopathic Hypercalcemia in Cats

Mild to moderate hypercalcemia that occurs in young/middle-aged cats

Ionized calcium is increases

NO ABNORMALITIES in PTH, PTH-rp, VitD

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Differential diagnosis: Hyperparathyroidism

Hypervitaminosis D

Typically hypercalcemia is present with hyperphophotemia in VitD toxicosis

Cholecalciferol rodenticide is a mojor cause of this disorder.

Toxicosis becomes severe within 48-72 hours,

Other sources: dermatologic ointments for people, over-supplementation of a patient with hypoparathyroidism, cestrum diurnum (daily blooming Jessamine) toxicosis

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Differential diagnosis: Hyperparathyroidism

Hypoadrenocortisism

serum calcium willbe increased in 30-50% of dogs/cats

Typically correlates well with serum potassium levels,

Not clinically important

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Differential diagnosis: Hyperparathyroidism

Chronic Renal Failure

Renal secondary hyperparathyroidism is a well-recognized phenomenon in chronic renal failure

results as a suppression of ionized calcium form the presence of hyperphophatemia

THESE PATIENTS NEVER HAVE ELEVATED IONIZED CALCIUM

total calcium may be elevated, not physiologically important to the patient

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Differential diagnosis: Hyperparathyroidism

Miscellaneous

bacterial/fungal osteomyelitis

blastomycosis

histoplasmosis

Schistosomiasis

Coccidiodomycosis

Sepsis

hypothermia

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Differential diagnosis: Hyperparathyroidism

Laboratory error:

Lipemia

Hemoconcentration

hemolysis

ALL can falsely elevate serum total calcium

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Hyperparathyroidism

Physical Examination

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PE often unremarkable

Occasionally, careful palpation of hte neck may reveal a nodule

Hyperparathyroidism

Diagnostic Imaging

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Parathyroid nodule detected by ultrasound of hte neck is supportive, but not diagnostic for hyperparathyroidism.

Nodules may only be found after surgical exploration

Hyperparathyroidism

Laboratory Evaluation

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Chemistry: elevation in total calcium and ionized calcium levels, Phosphorous is low

Hyperparathyroidism

Laboratory Evaluation

Inconsistent with Hyperparathyroidism

Cytopenia

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suppressiono fone or more cell types (RBC, WBC, Platelets) on the CBC may be associated with bone marrow infiltration in patitents with leukemia or lymphosarcoma

Hyperparathyroidism

Laboratory Evaluation

Inconsistent with Hyperparathyroidism

Serum Globulin Level

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marked elevations with multiple myeloma and some lymphomas

Hyperparathyroidism

Laboratory Evaluation

Inconsistent with Hyperparathyroidism

BUN/Creatinine

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Can be elevated in chornic renal failure, secondary to renal mineralization from prolonged hypercalcemia

or prerenal form PU with depressed fliud intake

Hyperparathyroidism Laboratory Evaluation Inconsistent with Hyperparathyroidism Phosphorous

Important to measure in all hypercalcemia cases Usually low or low-normal as a result of increased PTH, PTH-rp Hyperphophatemia without azotemia is more suggestive for VitD toxicosis or there nonparathyroid causes

Hyperparathyroidism Laboratory Evaluation Inconsistent with Hyperparathyroidism Potassium and Sodium Concentrations

Hyperkalemai and hyponatremia in combination suggest hypoadrenocorticism

Medical therapy for severe hypercalcemia any cause

treat: dehydration azotemia cardiac arrhythmias severe neurologic dysfunciton weakness

Acute therapy of hypercalcemia Useful in all cases

fluid therapy 0.9% NaCl saline diuresis promites renal calcium loss

Acute Therapy for Hypercalcemia Useful in some cases Furosemide

increases renal calcium excretion along with enhanced sodium excretion. inhibits Ca2+ resorption in the loop of henle.

Acute therapy for hypercalcemia useful in some cases Glucocorticoids

if possible, avoid the use of GC until a diagnosis has been established. GC decreases calcium resporption from bone, decreases intestinal Ca2+ absorption, increase renal Ca2+ excretion

Primary Hypoparathyroidism

occurs in dogs and cats but is much less common than Hyperparathyroidism

Major causes of Hypoparathyroidism

lumphocytic parathyroiditis, iatrogenic damage/removal of the parathyroid gland during thyroid surgery, as complication of parathyroidectomy for hyperparathyroidism

Hypoparathyroidism is characterized by

HYPOcalcemia

Hypocalcemia

infrequently recognized problem in dogs and cats increases tissue excitabliity in nervous and muscle tissue. signs are caused by a decrease in ionized calcium concentrations

Effects of Hypocalcemia

**peripheral neuromuscular signs** - tetany (prolonged muscle spasm) **Cardiac signs** - poor cardiac systolic function, cardiac dilation, bradycardia. Prolonged S-T, Q-T segments **Neurologic sings** - extrapyramidal neurologic syndromes and increased intracranial pressure **Ocular** - papilledema

Other causes of Hypocalcemia

chronic renal fialure acute pancreatitis puerperal tetany (Eclampsia) Intestinal malabsorption Nutritional hypoparathyroidism Acute renal fialure from Ethylene Glycol Toxicity Iatrogenic phosphate toxicity

Hypocalcemia due to hypoabluminemia

serum total calcium is often decreased in patients with hypoabluminemia. bound pool of calcium is decreased

How to correct calcium measurement with hypoalbumiemia

corrected calcium = measured total Ca + (3.5-albumin)

Hypoparathyroidism Physical Exam

nervousness seizures muscle cramping or pain (usually rear limbs) Focal muscle fasiculation / twitching Ataxia, stiff gait Intense facial rubbing, biting / licking at paws Aggression Panting Weakness Inappetence. listlessness, depression

Hypoparathyroidism Diagnostic imaging

Generally not used to make a diagnosis

Hypoparathyroidism Laboratory Evaluation

Most obvious finding ishte presence of severe hypocalcemia on the serum biochemistry profile. Measurement of ionized calcium may be helpful to confirm hypocalcemia when the total calcium is not obviously low. Phosphorous level is elevated

Results consistent with a diagnosis of Primary Hypoparathyroidism

decreased serum PTH, decreased ionized and total calcium. VIt D levels typically low

Comparison with Hypercalcemia disorders

Treatment of Hypoparathyroidism Emergency therapy

intravenous calcium given IV slowly over 10-20 minutes Monitor ECG during administration and briefly discontinue infusion if bradycardia develops

Treatment of Hypoparathyroidism Maintenance therapy Immediate

Repeated IV bolus injections NOT recommended Continuous IV infusion SQ calcium: AVOID if possible

Treatment of Hypoparathyroidism Maintentace therapy long term

vitamin D2 Dihydrotachysterol (DHT) Calcitriol Oral calcium supplementation

Parathyroid Disorders Flashcards

(46 cards)