Serum levels of inhibins are differentially altered in patients with polycystic ovary syndrome: effects of being overweight and relevance to hyperandrogenism

Fertil Steril. 2000 May;73(5):972-7. doi: 10.1016/s0015-0282(00)00421-0.

Abstract

Objective: To explore the abnormalities of serum inhibin isoform concentrations in a large group of patients with polycystic ovary syndrome (PCOS) and to evaluate the influence of body mass index (BMI), age, LH, and androgens on serum inhibin levels.

Design: Prospective study.

Setting: Reproductive endocrinology unit of an academic medical center.

Patient(s): Forty-one women with PCOS were compared with 24 healthy women.

Intervention(s): Blood sampling was performed in the early follicular phase in patients and in control women.

Main outcome measure(s): Serum levels of inhibin A, inhibin B, alpha-inhibin, pro-alphaC (alpha-inhibin precursor proteins), LH, FSH, E(2), T, and androstenedione (A) were assessed in all subjects.

Result(s): Serum alpha-inhibin levels together with LH, T, and A levels were significantly increased in women with PCOS. Serum inhibin A levels were lower in patients with PCOS than controls (median +/- SD: 7.35 +/- 2.9 vs. 9.4 +/- 4.7 pg/mL), pro-alphaC levels were higher (264 +/- 136.7 vs. 127 +/- 81.5 pg/mL), and inhibin B levels did not differ between the groups (110.5 +/- 51.5 vs. 108 +/- 47.5 pg/mL). Simple regression analysis showed that inhibin A and B levels were negatively correlated with BMI in patients with PCOS (r = -0.43 and r27 kg/m(2)) displayed significantly lower inhibin A and inhibin B levels and a higher pro-alphaC-inhibin A ratio than nonobese patients with PCOS (BMI </=27 kg/m(2)). In this last subgroup, the mean inhibin B level was significantly higher than in controls (median +/- SD: 144 +/- 53.5 vs. 108 +/- 47.5 pg/mL). Partial regression analysis, after controlling for age and BMI, demonstrated that in patients with PCOS, pro-alphaC levels were positively and independently correlated with LH and A levels.

Conclusion(s): Among women with PCOS, the trend toward an excess serum inhibin B level is observed exclusively in nonobese patients. The higher pro-alphaC levels and the lower inhibin A levels might reflect a defect in the processing of inhibins specific to polycystic ovaries. In addition, our data suggest that pro-alphaC originates from the theca-interstitial cells and could participate in control of the androgen production by these cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Androstenedione / blood
  • Body Mass Index
  • Estradiol / blood
  • Female
  • Humans
  • Hyperandrogenism / complications*
  • Inhibins / blood*
  • Luteinizing Hormone / blood
  • Obesity / complications*
  • Polycystic Ovary Syndrome / blood*
  • Polycystic Ovary Syndrome / complications
  • Protein Precursors / blood
  • Testosterone / blood

Substances

  • Protein Precursors
  • inhibin-alpha subunit precursor
  • Testosterone
  • Androstenedione
  • Estradiol
  • Inhibins
  • Luteinizing Hormone