In granulomatous disease, which hormone is increased independently of PTH that contributes to hypercalcemia?

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Multiple Choice

In granulomatous disease, which hormone is increased independently of PTH that contributes to hypercalcemia?

Explanation:
In granulomatous disease, hypercalcemia can arise from production of the active vitamin D form outside the kidneys. Macrophages within granulomas express 1α-hydroxylase, which converts calcidiol (the circulating storage form) into calcitriol (1,25-dihydroxyvitamin D) independently of PTH. This calcitriol increases intestinal absorption of calcium (and phosphate), elevating serum calcium even when PTH is low or suppressed. Calcitonin would oppose hypercalcemia and is not involved in this process, and calcidiol is just the substrate, not the hormone driving the rise. So the culprit hormone is calcitriol.

In granulomatous disease, hypercalcemia can arise from production of the active vitamin D form outside the kidneys. Macrophages within granulomas express 1α-hydroxylase, which converts calcidiol (the circulating storage form) into calcitriol (1,25-dihydroxyvitamin D) independently of PTH. This calcitriol increases intestinal absorption of calcium (and phosphate), elevating serum calcium even when PTH is low or suppressed. Calcitonin would oppose hypercalcemia and is not involved in this process, and calcidiol is just the substrate, not the hormone driving the rise. So the culprit hormone is calcitriol.

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