Abstract
Since calcium intake is inversely related to the risk of gestational hypertension and calcium supplementation reduces vascular sensitivity to angiotensin II, we determined by a specific electrode serum ionized calcium and calcium regulating hormones by radioassay in a French Caucasian population. During the third trimester of gestation we observed a significant decrease in ionized serum calcium in 22 mild to moderate hypertensive pregnant women without proteinuria compared to 15 normotensive pregnant control subjects (p<0.01). We also observed in this group elevated intact serum PTH and significant elevated carboxyterminal serum PTH within the nonpregnant normal range (p<0.05), but calcitonin and 1,25-dihydroxycnolecalciferol remained unchanged. It appears that activation of the parathyroid glands is secondary to the decrease of ionized serum calcium which may result from a general cellular defect in cationic exchange. The importance of these observations in the pathogenesis of gestational hypertensive disorders remains to be delineated.