Main inhibitor of follicle stimulating hormone in the luteal-follicular transition: inhibin A, oestradiol, or inhibin B?
The roles of oestradiol, inhibin A and inhibin B in the luteal-follicular transition were assessed by means of specific assays. Six premenopausal women were studied during a control and then a cycle treated with percutaneous oestradiol 0.1 mg/day from day 10 after the luteinizing hormone (LH) surge until day 4 of the following cycle. Inhibin A concentrations decreased similarly in control and treated cycles from day -5 to day 2, then increased in control cycle to 23.3 +/- 3.4 pg/ml on day 10 (mean +/- SEM). They remained low until day 5 in treated cycles and were lower than controls on day 10 (P < 0.01). Follicle stimulating hormone (FSH) concentrations increased on day 1 in controls and on day 5 in treated cycles when oestradiol concentration fell abruptly. Inhibin B concentrations remained low until day 1 in controls and day 4 in treated cycles. In both, inhibin B concentrations increased 1 day after FSH, peaking at 160 pg/ml. FSH concentrations began to plateau when inhibin B concentrations were >100 pg/ml and oestradiol concentrations below 200 pmol/l. These data suggest that inhibin A is not responsible for FSH suppression in the luteal phase and that the negative control of FSH shifts from oestradiol in the luteal phase to inhibin B in the mid-follicular phase.
D000328:Adult; D004958:Estradiol / Q000502:physiology*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000037:antagonists & inhibitors*; D005498:Follicular Phase; D006801:Humans; D007118:Immunoassay; D007265:Inhibins / Q000502:physiology*; D008183:Luteal Phase; D017697:Premenopause / Q000502:physiology; D020033:Protein Isoforms / Q000502:physiology*