In this study seven normal weight Indian patients with polycystic ovarian disease (PCOD) with no evidence of acanthosis nigricans and 7 age- and weight-matched normal Indian women were studied to determine whether PCOD patients were insulin-resistant. While all 14 women had normal glucose tolerance, the PCOD women had significantly higher mean plasma glucose levels at 30 and 60 min and higher mean incremental glucose areas [incremental areas: PCOD, 9.0 +/- 2.2 (+/- SEM); normal women, 4.0 +/- 0.8 mmol/L; P less than 0.05]. Insulin responses were significantly higher in the PCOD compared to normal women (incremental areas: PCOD, 623.8 +/- 78.3; normal women, 226.2 +/- 30.3 microU/mL; P less than 0.001). Both serum testosterone and androstenedione levels correlated with the insulin areas (r = 0.82; P less than 0.001 and r = 0.86; P less than 0.001, respectively). [125I] Insulin binding to erythrocytes revealed decreased maximum specific binding in the PCOD women (6.9 +/- 0.6%) compared to that in normal women (9.2 +/- 0.7%; P less than 0.02). While Scatchard analysis revealed similar receptor numbers, ID50 values demonstrated decreased receptor affinity in the women with PCOD. In conclusion, in the absence of acanthosis nigricans, nonobese patients with PCOD are insulin resistant, and this insulin resistance correlates with the hyperandrogenism.

Inhibin production by the corpus luteum was investigated by undertaking pharmacological rescue of the corpus luteum with hCG in four healthy women. Blood samples were collected daily for two menstrual cycles. Starting 7 days after the LH surge in the second cycle, incremental doses of hCG (125-8000 IU) were administered daily for 7 days resulting in hCG levels comparable to those seen in normal pregnancy. Following hCG, the luteal phase was prolonged and there were significant increases in the plasma concentrations of inhibin ( P < 0-05), and oestradiol (P< 0-05). The progesterone concentration was maintained at the mid-luteal phase peak and as a result was significantly higher than those on the equivalent days of the control cycle (P

To examine the relationship between circulating levels of bioactive FSH (B-FSH) and immunoactive inhibin and oestradiol we studied five women during ovulatory cycles. Daily blood samples were collected from each subject during one menstrual cycle. B-FSH was measured using a modified, highly sensitive in-vitro rat granulosa cell bioassay. The inclusion of IGF-1 (10 micrograms/l) and transferrin (50 mg/l) in the assay system enhanced granulosa cell responsiveness to FSH and resulted in increased assay sensitivity. Inhibin was measured by a heterologous radioimmunoassay (RIA) using an antibody raised against 31 kDa bovine inhibin. Bioactive FSH (B-FSH) levels were closely correlated to those of immunoactive FSH (I-FSH, r = 0.79, P less than 0.001) throughout the cycle. Peak levels of B-FSH were observed during the early follicular phase (day -13, 44.7 +/- 9.6 IU/l, mean +/- SEM) and during the midcycle surge (35.2 +/- 6.2 IU/l); lowest levels occurring during the luteal phase (nadir 3.9 +/- 0.27 IU/l). Plasma oestradiol levels increased significantly during the follicular phase (P less than 0.001) to a peak on day -1 and were negatively correlated with B-FSH during the late follicular phase (day -8 to -1; r = -0.45, P less than 0.02). There was no change in the concentration of inhibin (range 55.3-72.3 U/l) during the follicular phase until day -2 after which an increase to a midcycle peak of 139 +/- 10.6 U/l was observed. No correlation was observed between inhibin and B-FSH during the follicular phase. A second increase in the concentration of inhibin was seen during the luteal phase; peak levels occurred by day 6 (311 +/- 25.8 U/l), remained elevated until day 12, and were negatively correlated with B-FSH (r = -0.53, P less than 0.001). No correlation was observed between oestradiol and inhibin or B-FSH during the luteal phase. We conclude that (1) oestradiol secretion from the growing follicle is primarily responsible for the negative feedback regulation of B-FSH resulting in a change from peak levels in the early follicular phase to basal levels in the late follicular phase; (2) significant and sustained increase in peripheral inhibin concentrations occur mostly during the luteal phase; and (3) regulation of FSH secretion by inhibin occurs primarily in the luteal phase. These results suggest a temporal relationship between oestradiol and inhibin in the negative feedback regulation of FSH in vivo.