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.
Winters
Stephen J
SJ
Department of Medicine, University of Louisville, Louisville, Kentucky 40202, USA. sjwint01@louisville.edu
Wang
Chenxi
C
Abdelrahaman
Eiman
E
Hadeed
Venus
V
Dyky
Mary Ann
MA
Brufsky
Adam
A
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