Relationship of estrogen and pregnancy to calcium homeostasis in pseudohypoparathyroidism.
The relationship of estrogen administration and pregnancy to vitamin D metabolism and Ca homeostasis was examined in two young women with pseudohypoparathyroidism. Estrogen, which is believed to inhibit PTH-mediated bone resorption, caused a consistent dose-related reversible reduction of serum Ca in these patients. This finding supports the concept that PTH-mediated bone resorption may contribute to the maintenance of serum Ca in normocalcemic pseudohypoparathyroidism. Paradoxically, these two patients remained normocalcemic throughout pregnancy, a high estrogen state. They were studied during four pregnancies, and each time a similar pattern emerged. Despite a primary derangement of the renal 1 alpha-hydroxylase, serum 1,25-dihydrovitamin D [1,25-(OH)2D] concentration increased 2- to 3-fold, while the serum PTH level was nearly halved during pregnancy. After delivery, serum Ca and 1,25-(OH)2D decreased, and serum PTH rose appropriately. Placental synthesis of 1,25-(OH)2D may have contributed to the maintenance of normocalcemia in these patients.
D000328:Adult; D002112:Calcifediol / Q000097:blood; D002117:Calcitriol / Q000097:blood; D002118:Calcium / Q000097:blood*; D002132:Calcium Radioisotopes; D004997:Ethinyl Estradiol; D005260:Female; D006706:Homeostasis; D006801:Humans; D010281:Parathyroid Hormone / Q000097:blood; D010710:Phosphates / Q000097:blood*; D011247:Pregnancy; D011248:Pregnancy Complications / Q000097:blood*; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D011547:Pseudohypoparathyroidism / Q000097:blood* / Q000150:complications
D002132:Calcium Radioisotopes; D010281:Parathyroid Hormone; D010710:Phosphates; D004997:Ethinyl Estradiol; D002117:Calcitriol; D002112:Calcifediol; D002118:Calcium