Longitudinal effects of aging on serum total and free testosterone levels in healthy men. Baltimore Longitudinal Study of Aging

  • Harman S
  • Metter E
  • Tobin J
 et al. 
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Abstract

Many studies have shown cross-sectional (and two small studies, longitudinal) declines in total and/or free testosterone (T) levels, with age, in men. The extent to which decline in T is the result of the aging process per se, as opposed to chronic illness, medication use, and other age-related factors, remains controversial. The frequency with which aging leads to T levels consistent with hypogonadism has also not been defined. These issues bear on the potential use of T replacement in aging men, because aging and hypogonadism have, in common, reduced bone and lean body mass and muscle strength and increased total and abdominal fat. We measured T and sex hormone-binding globulin (SHBG), by RIA, in stored samples from 890 men in the Baltimore Longitudinal Study on Aging. Using a mixed-effects model, we found independent effects of age and date of sampling to reduce T levels. After compensating for date effects, which investigation suggested was artifactual, we observed significant, independent, age-invariant, longitudinal effects of age on both T and free T index (free T index = T/SHBG), with an average change of -0.124 nmol/L.yr and -0.0049 nmol T/nmol SHBG.yr. T, but not free T index, also decreased with increasing body mass index. Use of beta-blocking drugs was associated with higher T and higher free T index levels. Using total T criteria, incidence of hypogonadal T levels increased to about 20% of men over 60, 30% over 70 and 50% over 80 yr of age, and even greater percentages when free T index criteria were employed. Our observations of health factor independent, age-related longitudinal decreases in T and free T, resulting in a high frequency of hypogonadal values, suggest that further investigation of T replacement in aged men, perhaps targeted to those with the lowest serum T concentrations, are justified

Author-supplied keywords

  • Adult
  • Aged
  • Aging
  • Baltimore
  • Body Mass Index
  • European Continental Ancestry Group
  • HEALTH
  • Humans
  • Hypogonadism
  • Incidence
  • Longitudinal Studies
  • MEN
  • Male
  • Middle Aged
  • Radioimmunoassay
  • Regression Analysis
  • Reproducibility of Results
  • Research
  • Sex Hormone-Binding Globulin
  • Social Class
  • Testosterone
  • analysis
  • blood
  • epidemiology

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  • PMID: 11158037

Authors

  • S M Harman

  • E J Metter

  • J D Tobin

  • J Pearson

  • M R Blackman

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