Inhibin-B levels in healthy young adult men and prepubertal boys: is obesity the cause for the contemporary decline in sperm count because of fewer Sertoli cells?
Inhibin-B is a heterodimeric glycoprotein produced by Sertoli cells. Although inhibin-B levels are low when seminiferous tubules are damaged, studies in normal monkeys reveal that inhibin-B levels also correlate positively with Sertoli cell number. In this study, we measured inhibin-B levels in healthy young adult men aged 18-24 years and in prepubertal boys aged 5-9 years in relation to body mass index (BMI). Inhibin-B levels declined with increasing obesity in young adult men; values were 26% lower in men who were obese compared to normal-weight men. Sex hormone-binding globulin and total testosterone, but not free testosterone, were also lower with increasing BMI; serum follicle-stimulating hormone and luteinizing hormone levels were unaffected by obesity. In prepubertal boys, by contrast, inhibin-B was unaffected by obesity. We propose that reduced levels of inhibin-B indicate that obese men have fewer Sertoli cells than men of normal weight. Moreover, normal values in obese prepubertal boys suggest that the effect of obesity on inhibin-B is established during puberty. Finally, because each Sertoli cell is thought to support a finite number of germ cells, fewer Sertoli cells in obesity may predispose to a lower sperm count in adulthood. We speculate that the escalating prevalence of obesity and insulin resistance among adolescents might negatively influence male reproductive function for the next generation.
Department of Medicine, University of Louisville, Louisville, Kentucky 40202, USA. sjwint01@louisville.edu
Stephen J
SJ
Winters
Chenxi
C
Wang
Eiman
E
Abdelrahaman
Venus
V
Hadeed
Mary Ann
MA
Dyky
Adam
A
Brufsky
D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D002452:Cell Count; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007265:Inhibins / Q000097:blood*; D008297:Male; D009765:Obesity / Q000097:blood*; D011627:Puberty / Q000097:blood; D012708:Sertoli Cells / Q000166:cytology*; D012738:Sex Hormone-Binding Globulin / Q000032:analysis; D013076:Sperm Count; D013739:Testosterone / Q000097:blood
D012738:Sex Hormone-Binding Globulin; C422364:inhibin B; D013739:Testosterone; D007265:Inhibins