Changes in BMI modulate age-associated changes in sex hormone binding globulin and total testosterone, but not bioavailable testosterone in young adult men: the CARDIA Male Hormone Study

Int J Obes (Lond). 2007 Apr;31(4):685-91. doi: 10.1038/sj.ijo.0803465. Epub 2006 Sep 12.

Abstract

Objectives: To compare age-associated 8-year changes in total testosterone, calculated bioavailable testosterone and sex hormone binding globulin (SHBG) across five groups of men stratified according to change in body mass index (BMI) (i.e., BMI stable (+/-0.69 kg/m(2)), decreased (-0.7 kg/m(2)), increased minimally (0.7-1.74 kg/m(2)), increased moderately (1.75-3.19 kg/m(2)) and increased most (> or =3.20 kg/m(2))).

Design: Eight-year longitudinal cohort study.

Subjects: Four hundred and seventy-four black and 695 white men, aged 24-31 years at the time of the first hormone measurement.

Measurements: Aging-related changes in serum SHBG, total testosterone and bioavailable testosterone.

Results: SHBG significantly increased with age for men whose BMI decreased, and there were progressively smaller increases for men whose BMI was stable, or whose BMI increased minimally or moderately (range 1.1-0.3 nM per year, P< or =0.03, respectively). There was no age relationship with SHBG among men whose BMI increased most. Total testosterone did not change with age for men whose BMI decreased, was stable or increased minimally, but for men whose BMI increased moderately and most there was a graded decrease in total testosterone with age (beta=-0.2 and -0.4 nM per year, respectively, P< or =0.005). However, bioavailable testosterone decreased with age to a similar extent across all groups.

Conclusions: These results suggest that changes in BMI during young adulthood modulate age-related changes in SHBG and total testosterone, but not bioavailable testosterone.

Publication types

  • Multicenter Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • African Continental Ancestry Group
  • Aging / ethnology
  • Aging / physiology*
  • Biological Availability
  • Body Mass Index*
  • Body Weight / physiology
  • European Continental Ancestry Group
  • Humans
  • Longitudinal Studies
  • Male
  • Sex Hormone-Binding Globulin / analysis*
  • Testosterone / blood*
  • Testosterone / pharmacokinetics

Substances

  • Sex Hormone-Binding Globulin
  • Testosterone