The most impoant regulator of serum 1,25 (OH)2 vitamin D concentration is
High-Yield Explanation
A major function of parathyroid hormone is to act as a trophic hormone to regulate the rate of formation of 1,25(OH)2 vitamin D. The mechanism by which parathyroid hormone exes this effect may be secondary to its effects on phosphorus metabolism. Other hormones, including prolactin and estrogen, also may playa role in stimulating the production of 1,25(OH)2 vitamin D. Ref - Harrison's internal medicine 20e pg bone effects of PTH 2956-2957 PTH in calcium homeostasis, 2095, 2912, 2931f