Reference ranges for testosterone in men generated using liquid chromatography tandem mass spectrometry in a community-based sample of healthy nonobese young men in the Framingham Heart Study and applied to three geographically distinct cohorts

Abstract

Context: Reference ranges are essential for partitioning testosterone levels into low or normal and making the diagnosis of androgen deficiency. We established reference ranges for total testosterone (TT) and free testosterone (FT) in a community-based sample of men.

Methods: TT was measured using liquid chromatography tandem mass spectrometry in nonobese healthy men, 19-40 yr old, in the Framingham Heart Study Generation 3; FT was calculated. Values below the 2.5th percentile of reference sample were deemed low. We determined the association of low TT and FT with physical dysfunction, sexual symptoms [European Male Aging Study (EMAS) only], and diabetes mellitus in three cohorts: Framingham Heart Study generations 2 and 3, EMAS, and the Osteoporotic Fractures in Men Study.

Results: In a reference sample of 456 men, mean (sd), median (quartile), and 2.5th percentile values were 723.8 (221.1), 698.7 (296.5), and 348.3 ng/dl for TT and 141. 8 (45.0), 134.0 (60.0), and 70.0 pg/ml for FT, respectively. In all three samples, men with low TT and FT were more likely to have slow walking speed, difficulty climbing stairs, or frailty and diabetes than those with normal levels. In EMAS, men with low TT and FT were more likely to report sexual symptoms than men with normal levels. Men with low TT and FT were more likely to have at least one of the following: sexual symptoms (EMAS only), physical dysfunction, or diabetes.

Conclusion: Reference ranges generated in a community-based sample of men provide a rational basis for categorizing testosterone levels as low or normal. Men with low TT or FT by these criteria had higher prevalence of physical dysfunction, sexual dysfunction, and diabetes. These reference limits should be validated prospectively in relation to incident outcomes and in randomized trials.

Fig. 1.

The STROBE diagram: selection of the FHS reference sample. Of the 1912 men who attended the first Gen 3 examination (2002–2005), 1893 had total testosterone measurements, 962 were 40 yr of age or younger, and 456 men were free of cancer, CVD, DM, hypertension, hypercholesterolemia, obesity, and smoking.

Fig. 2.

Distribution of total and free testosterone levels by decades of age in the FHS broad sample as well as the EMAS and MrOS validation samples. Means and sd bars are shown. To convert total testosterone from nanograms per deciliter to nanomoles per liter, multiply concentrations in nanograms per deciliter by 0.0347. To convert free testosterone from picograms per milliliter to picomoles per liter, multiply concentrations in picograms per milliliter by 3.47.

Fig. 3.

Association of low total or free testosterone with sexual symptoms, physical dysfunction, DM, or any one of these conditions in the FHS, EMAS, and MrOS cohorts. The odds ratios along with the 95% confidence intervals for the association of total and free testosterone with various outcomes in the three validation cohorts are shown. The composite outcome indicates the following: in FHS, one or more of slow walking speed (walking speed in the lowest 20th percentile), self-reported mobility limitation, or diabetes; in EMAS, one or more of low frequency of morning erections, erectile dysfunction, low frequency of sexual thoughts, difficulty in climbing several stairs, limited in walking more than 1 km, slow walking speed (walking speed in the lowest 20th percentile), or diabetes; in MrOS, one or more of frailty, slow walking speed (walking speed in the lowest 20th percentile), or diabetes.