Obesity and serum luteinizing hormone level have an independent and opposite effect on the serum inhibin B level in patients with polycystic ovary syndrome.
OBJECTIVE
To elucidate whether the negative effect of obesity on the serum inhibin B level that we previously reported is specific or not to polycystic ovary syndrome (PCOS) and whether it may explain the wide interindividual variability in serum inhibin B levels found in patients with PCOS.


METHODS
Prospective study.


METHODS
Reproductive endocrinology unit of an academic medical center.


METHODS
One hundred thirty-four consecutive patients with PCOS (mean age, 27.4 +/- 4.7 years; mean body mass index [BMI], 28.3 +/- 7.6 kg/m(2); BMI > 25, 53%) and in 78 control women (mean age, 30.1 +/- 4.1 years; mean BMI, 24.3 +/- 4.9; BMI > 25, 34%).


METHODS
Blood sampling was performed in the early follicular phase in patients and in control women.


METHODS
BMI and waist circumference (WC), serum levels of inhibin B, LH, FSH, E(2), androstenedione, T, fasting insulin, and leptin were assessed in all subjects.


RESULTS
No difference was observed in the mean inhibin B level between patients and controls. The BMI and WC correlated negatively with inhibin B in patients with PCOS and in controls, with similar regression slopes, thus indicating that the influence of obesity on inhibin B is not specific to PCOS. In addition, we found a positive relationship between serum LH and inhibin B levels in PCOS. There was no significant interaction between the effects of BMI and LH on the serum inhibin B levels by analysis of variance (ANOVA). The mean serum inhibin B level in patients with PCOS with high serum LH (i.e., >the 90th percentile of LH in controls) was significantly higher than in those patients with normal LH or in controls. The highest mean inhibin B level was noted in nonobese patients with PCOS with high LH levels (121.0 +/- 51.2 pg/mL), while nonobese patients with PCOS with normal LH levels and obese patients with normal LH or high LH levels had similar mean levels (94.5 +/- 40.0, 84.9 +/- 34 and 91.6 +/- 51.7 pg/mL, respectively).


CONCLUSIONS
We confirm that obesity has a negative effect on inhibin B serum level, which is not specific to PCOS. Obesity and excess LH, acting oppositely and independently on inhibin B production, may explain the discrepancies between the previous reports studying serum inhibin B level in patients with PCOS. Further work is required to elucidate the mechanisms underlying the antagonistic effects of LH and obesity on inhibin B production in patients with PCOS.
Cortet-Rudelli
Christine
C
Department of Diabetology and Endocrinology, Clinique Marc Linquette, C.H.R.U., 59037 Lille, France.
Pigny
Pascal
P
Decanter
Christine
C
Leroy
Maryse
M
Maunoury-Lefebvre
Catherine
C
Thomas-Desrousseaux
Patricia
P
Dewailly
Didier
D
D000293:Adolescent; D000328:Adult; D000735:Androstenedione / Q000097:blood; D015992:Body Mass Index; D004958:Estradiol / Q000097:blood; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006801:Humans; D007124:Immunoenzyme Techniques; D007265:Inhibins / Q000096:biosynthesis / Q000097:blood*; D007328:Insulin / Q000097:blood; D020738:Leptin / Q000097:blood; D007986:Luteinizing Hormone / Q000097:blood*; D009765:Obesity / Q000097:blood*; D011085:Polycystic Ovary Syndrome / Q000097:blood*; D011446:Prospective Studies; D013739:Testosterone / Q000097:blood
D007328:Insulin; D020738:Leptin; C422364:inhibin B; D013739:Testosterone; D000735:Androstenedione; D004958:Estradiol; D007265:Inhibins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone