Hypercalcemia is decreased by all of the following EXCEPT: March 2003, 2007
Hypercalcemia can be due to hyperparathyroidism, cancer, vitamin D toxicity, or other causes. The body lowers calcium through various mechanisms. For example, PTH (parathyroid hormone) increases calcium by acting on bones, kidneys, and intestines. So, if something inhibits PTH, that would lower calcium. Also, calcitonin is a hormone that decreases blood calcium by inhibiting osteoclasts. Diuretics like loop diuretics (furosemide) can increase calcium excretion, thus lowering levels. On the other hand, thiazide diuretics actually decrease calcium excretion and can cause hypercalcemia. So if an option includes thiazides, that would be the exception here.
Wait, the question is asking for the exception—what does NOT decrease hypercalcemia. So the correct answer is the one that actually increases or doesn't lower calcium. Let me think of the options. If one of the options is thiazide diuretics, that's the answer because they reduce calcium excretion. Other options might include bisphosphonates, which inhibit osteoclasts, so they lower calcium. Glucocorticoids can help in certain types of hypercalcemia like due to sarcoidosis. So the incorrect options would be the ones that lower calcium, and the correct answer is the one that doesn't. So the answer is thiazide diuretics. Let me confirm: thiazides decrease calcium excretion, so they can worsen hypercalcemia. Therefore, thiazides would be the exception here. So the correct answer would be the option that includes thiazide diuretics.
**Core Concept**
Hypercalcemia management involves agents that reduce serum calcium by inhibiting bone resorption, enhancing renal excretion, or modulating vitamin D metabolism. The exception is a drug that paradoxically reduces calcium excretion or stimulates resorption.
**Why the Correct Answer is Right**
Thiazide diuretics (e.g., hydrochlorothiazide) **decrease renal calcium excretion** by promoting sodium reabsorption in the distal convoluted tubule, leading to reduced calcium clearance. This exacerbates hypercalcemia rather than lowering it. Unlike loop diuretics (e.g., furosemide), which increase calcium excretion, thiazides are contraindicated in hypercalcemic states.
**Why Each Wrong Option is Incorrect**
**Option A:** Bisphosphonates inhibit osteoclast-mediated bone resorption, reducing calcium release into the blood.
**Option B:** Calcitonin suppresses osteoclast activity and enhances renal calcium excretion, effectively lowering serum calcium.
**Option C:** Glucocorticoids (e.g., prednisone) decrease intestinal calcium absorption and suppress 1,25-dihydroxyvitamin D synthesis in granulomatous diseases, reducing hypercalcemia.
**Clinical Pearl / High-Yield Fact**
Thiazide diuretics are a classic exam trap in hypercalcemia questions. Remember: **"Thiazides thieve calcium,"** worsening hypercalcemia by reducing renal excretion