Calcium-regulating hormones across the menstrual cycle: evidence of a secondary hyperparathyroidism in women with PMS

Abstract

Calcium metabolism across one menstrual cycle was studied in 12 healthy, premenopausal women. Seven women had documented premenstrual syndrome (PMS), and five were asymptomatic controls. Fasting blood samples were drawn at six points throughout the ovulatory cycle. In both the asymptomatic and the PMS groups, total and ionized calcium declined significantly at midcycle with the increase of estradiol. In the PMS group only, peak midcycle intact PTH was significantly elevated by approximately 30% compared with early follicular levels (49 +/- 25 vs. 37 +/- 22 ng/L, t = 3.79, P = 0.009). In the asymptomatic group, iPTH did not vary during the menstrual cycle. Midcycle iPTH was significantly higher in the PMS group compared with that of the control group (49 +/- 25 vs. 26 +/- 7 ng/L, Wilcoxon Z = 2.28, P = 0.02). Multivariate analysis showed that total and ionized calcium both varied significantly across the menstrual cycle. Significant differences between groups were found for total calcium, 25OHD, and 1,25-(OH)2D. One woman with PMS was treated with oral elemental calcium and cholecalciferol daily for 3 months, with amelioration of her symptoms. Midcycle iPTH and 1,25-(OH)2D declined after repletion of 25OHD. In conclusion, we found that concentrations of total and ionized calcium significantly fluctuate during the menstrual cycle both in symptomatic and in asymptomatic women. We also found that concentrations of iPTH, 25OHD, and 1,25-(OH)2D differed between groups during specific phases of the menstrual cycle. Our data suggest that women with PMS have midcycle elevations of iPTH with a transient, secondary hyperparathyroidism.