Plasma proinsulin, C-peptide and sex hormone concentrations in regularly menstruating premenopausal females with ovulatory and anovulatory menstrual cycles.

AIM

Highly active females are at risk of athletic menstrual irregularities including anovulatory menstrual cycles, oligomenorrhea and even amenorrhea. On the other hand, the functional relationship between endocrine pancreas and ovaries is supported by numerous studies indicating that disturbed female sex hormone secretion coexists with insulin resistance and glucose intolerance. However, the relationship between circulating beta islet and ovarian hormones in regularly menstruating active women with ovulatory and anovulatory menstrual cycle has not been studied.

METHODS

A total of 32 regularly menstruating women participated in the study. Prospective subjects monitored their BBT for 3 months before the study. The determination of plasma progesterone levels between days 5-8 and again between days 19-22 of the menstrual cycles made possible the classification of subjects as ovulating or non-ovulating. Plasma 17-beta-estradiol, testosterone, insulin, proinsulin, C-peptide and glucose concentrations were assayed on the same menstrual cycle days as progesterone.

RESULTS

There were no differences in circulating insulin, C-peptide and glucose between non-ovulating and ovulating women. In contrast, in non-ovulating subjects plasma proinsulin concentrations between days 19-22 were slightly, but significantly higher than between days 5-8 of the menstrual cycle (P<0.05). Exclusively in non-ovulating women significant and positive correlation was noted between circulating proinsulin and 17-beta-estradiol in data collected from both days 5-8 and 19-22 of the menstrual cycle (P<0.008).

CONCLUSIONS

Our results indicate that in the face of low circulating progesterone and subsequent anovulation circulating 17-beta-estradiol slightly, but significantly, affect either pancreatic beta-cell biosynthetic activity or proinsulin hepatic and/or renal clearance.