Androgens and Osteocalcin during the Menstrual Cycle1

The relationship between physiological variations in female sex and androgenic hormones and calciotropic hormones was investigated during the menstrual cycle. Estradiol, progesterone, total and free testosterone, androstenedione, immunoreactive PTH, calcitonin, osteocalcin (OC), and ionized calcium serum levels were determined throughout the menstrual cycle in a population of healthy eumenorrhoic women (n = 12; age range: 20-29 yr; mean: 24.2 yr). The women were studied from the first day of a menstrual phase until the first day of the following menstrual phase. Cycle length was standardized on the preovulatory estradiol peak (day 0), and values were given for the first day of a menstrual phase, and days -12, -10, -8, -6, -4, -2, 0, 2, 4, 6, 8, 10, 12, and 14 of the menstrual cycle. All subjects had a regular ovulatory cycle, as indicated by the hormonal profile. No significant cycle phase-dependent changes in calciotropic hormones were present. Significant positive correlations between total testosterone (r = 0.32, P < 0.001), free testosterone (r = 0.26, P < 0.001), androstenedione (r = 0.35, P < 0.0001), and OC were observed. The significant relations between these variables were confirmed by a time series analysis. For the first time, these findings indicate a relationship between androgens and OC serum levels during the menstrual cycle. An important regulatory role of endogenous androgens in OC secretion, bone formation, and maintenance of normal bone mineral content in the healthy eumenorrhoic woman is hence suggested.