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J Clin Endocrinol Metab. 2007 Jan;92(1):196-202. Epub 2006 Oct 24.

A population-level decline in serum testosterone levels in American men.

Author information

  • 1New England Research Institutes, 9 Galen Street, Watertown, Massachusetts 02472, USA. ttravison@neriscience.com

Abstract

CONTEXT:

Age-specific estimates of mean testosterone (T) concentrations appear to vary by year of observation and by birth cohort, and estimates of longitudinal declines in T typically outstrip cross-sectional decreases. These observations motivate a hypothesis of a population-level decrease in T over calendar time, independent of chronological aging.

OBJECTIVE:

The goal of this study was to establish the magnitude of population-level changes in serum T concentrations and the degree to which they are explained by secular changes in relative weight and other factors.

DESIGN:

We describe a prospective cohort study of health and endocrine functioning in randomly selected men of age 45-79 yr. We provide three data collection waves: baseline (T1: 1987-1999) and two follow-ups (T2: 1995-1997, T3: 2002-2004).

SETTING:

This was an observational study of randomly selected men residing in greater Boston, Massachusetts.

PARTICIPANTS:

Data obtained from 1374, 906, and 489 men at T1, T2, and T3, respectively, totaling 2769 observations taken on 1532 men.

MAIN OUTCOME MEASURES:

The main outcome measures were serum total T and calculated bioavailable T.

RESULTS:

We observe a substantial age-independent decline in T that does not appear to be attributable to observed changes in explanatory factors, including health and lifestyle characteristics such as smoking and obesity. The estimated population-level declines are greater in magnitude than the cross-sectional declines in T typically associated with age.

CONCLUSIONS:

These results indicate that recent years have seen a substantial, and as yet unrecognized, age-independent population-level decrease in T in American men, potentially attributable to birth cohort differences or to health or environmental effects not captured in observed data.

PMID:
17062768
[PubMed - indexed for MEDLINE]
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