Serum inhibin-b in fertile men is strongly correlated with low but not high sperm counts: a coordinated study of 1,797 European and US men

Fertil Steril. 2010 Nov;94(6):2128-34. doi: 10.1016/j.fertnstert.2009.12.051. Epub 2010 Feb 10.


Objective: To describe associations between serum inhibin-b and sperm counts, adjusted for effect of time of blood sampling, in larger cohorts than have been previously reported.

Design: Cross-sectional studies of spermatogenesis markers.

Setting: Four European and four US centers.

Patient(s): Fertile men (1,797) were included and examined from October 1996-February 2005.

Intervention(s): The study was observational and therefore without any intervention.

Main outcome measure(s): Associations between inhibin-b and semen variables controlled for time of blood sampling and other covariates.

Result(s): Inhibin-b decreased about 2.00% per hour from 8 am-12 pm and then about 3.25% per hour from 12 pm-4 pm. There was a strong positive association between inhibin-b levels less than 150 pg/mL and both sperm concentration and total sperm count (slopes of the regression lines were β=0.011 and β=0.013 for natural logarithm-transformed sperm concentration and total sperm count, respectively). For inhibin-b levels of 150-300 pg/mL the associations were not as steep (β=0.002), but still significant. For inhibin-b levels more than 300 pg/mL there was little association to the sperm counts. Neither sperm motility nor morphology was significantly related to inhibin-b level in any group.

Conclusion(s): Serum inhibin-b levels decrease nonlinearly during the daytime, and are positively correlated with sperm counts, but the predictive power is best when inhibin-b is low.

Publication types

  • Comparative Study
  • Evaluation Study
  • Multicenter Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Biomarkers / blood
  • Blood Specimen Collection
  • Circadian Rhythm / physiology
  • Cross-Sectional Studies
  • Europe / epidemiology
  • Fertility* / physiology
  • Humans
  • Inhibins / blood*
  • Male
  • Middle Aged
  • Oligospermia / blood*
  • Oligospermia / diagnosis
  • Oligospermia / epidemiology
  • Predictive Value of Tests
  • Sperm Count*
  • Time Factors
  • United States / epidemiology
  • Young Adult


  • Biomarkers
  • inhibin B
  • Inhibins