Disorders of Calcium Metabolism Flashcards
PTH increases serum calcium by four ways: _________________.
increased bone resorption; increased intestinal absorption; decreased renal excretion; and increased renal resorption
What is the major storage form of vitamin D?
25-hydroxy vitamin D (in the liver)
What enzyme in the kidney activates vitamin D?
1-alpha hydroxylase
To assess for deficiency, we measure ________________.
the storage form of vitamin D
Vitamin D has a similar effect as parathyroid hormone. How do they differ?
Vitamin D increases phosphate levels, while PTH decreases phosphate levels
What are the two most common causes of hypercalcemia?
Primary hyperparathyroidism and malignancy (these account for 90% of hypercalcemias)
What are some less common causes of hypercalcemia?
Exogenous vitamin D toxicity Exogenous vitamin A toxicity Hyperthyroidism Granulomatous disease Thiazide diuretics Milk-alkali syndrome Immobilization Adrenal insufficiency Acute renal failure Familial hypocalciuric hypercalcemia
What is the first step in evaluating hypercalcemia?
Measure PTH: there are only two disorders where it’s high (primary hyperparathyroidism and familial hypercalcemia)
What are brown tumors?
They are overgrowths of osteoclasts that occur in response to extremely elevated levels of parathyroid hormone (such as from a parathyroid adenoma)
Most people with hyperparathyroidism have what symptoms?
None, most are asymptomatic
What might you see in a CBC of someone with hyperparathyroidism?
Anemia (because PTH suppresses erythropoiesis)
Someone with primary hyperparathyroidism might have lines in their joint spaces. What are these?
Chondocalcinosis
Most of the cases of hyperparathyroidism are ___________.
sporadic (10%)
MEN I is the disorder of three Ps: __________________.
pituitary adenoma, pancreatic endocrine tumors, and hyperParathyroidism
What is the genetic cause of MEN I?
Defects in the Menin gene (MEN1n… get it?)
