Calcium-Regulating Hormones across the Menstrual Cycle*

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Abstract
Midcycle elevations of serum PTH, calcitonin (CT), and 1,25–dihydroxyvitaminD [1,25–(OH)2D] in women have been reported. To examine the effects of cyclic changes inovarian steroid secretion on calcitropic hormone concentrations, we used a cytoreceptor assay for 1,25–(OH)2D and homologous RIAs for PTH and CT to measure these hormones in dailyblood samples obtained from six women throughout the menstrual cycle. Significant changesin serum PTH, CT, 1,25–(OH)2D, calcium, and phosphorus concentrations during the cycle were not found; transverse means (±SE) were 101 ± 3.5 pg⁄ml for PTH, 30.8 ± 1.8 pg⁄ml for CT, and 40.1 ± 1.7 pg⁄ml for 1,25–(0H)2D. In addition, CT reserve was assessed by calcium infusion (3 mg⁄kg, iv, in 10 min) during the early and late follicular and midlutealphases of the cycle. Although serum CT increased significantly (P < 0.01) after calcium infusion, the mean (±SE) increment (23.2 ± 2.2 pg⁄ml) did not significantly differ in thethree phases of the cycle (early follicular, 23.8 ± 4.0; late follicular,23.3 ± 3.4; midluteal, 22.5 ± 4.1). Our data do not support previous reports of midcycleelevations in serum PTH, CT, and 1,25–(OH)2D concentrations, and we conclude that serum concentrations ofthe calcitropic hormones do not significantly vary during the menstrual cycle. (J Clin Endocrinol Metab62: 1313,1986)