Serum Concentrations of Sex Hormone-binding Globulin Vary Widely in Younger and Older Men: Clinical Data from a Men's Health Practice

Abstract

Background: The testosterone (T) status of a man is influenced by serum concentrations of sex hormone-binding globulin (SHBG). Specifically, tight binding of T to SHBG is believed to render the SHBG-bound T fraction biologically unavailable, meaning that interpretation of T levels in the clinical setting depends in part on knowledge of SHBG concentrations. Although SHBG levels have been reported in population studies, there is scant information for men presenting with clinical symptoms.

Objective: To report SHBG values for a large cohort of men presenting to a men's health center.

Design, setting, and participants: Medical records were reviewed for 1000 consecutive patients seen at our center with a reported SHBG value. SHBG concentrations were measured by a national clinical laboratory using an immunoassay run on a Beckman Coulter DXi system.

Outcome measurements and statistical analysis: Patients were age-stratified and data were plotted in the form of comparative histograms.

Results and limitations: The mean age (±standard deviation) of the total cohort was 53.5±13.5 yr (range 17-91). The mean SHBG was 31.8±15.2nmol/l (range 6-109), with a nearly 20-fold difference from the lowest to the highest values. SHBG was >60nmol/l in 5.6% of the men. Patients were stratified according to age. A total of 535 patients were ≤54 yr old. In this younger cohort, the mean age was 40.52±7.9 yr (range 17-54) and mean SHBG was 27.7±13.3nmol/l (range 6-88), and 2.2% of patients had SHBG >60nmol/l. A total of 465 patients were ≥55 yr old. In this older cohort, the mean age was 64.8±7.23 yr (range 55-91) and mean SHBG was 36.6±15.8 nmol/l (range 11-109), and 9% of patients had SHBG >60 nmol/l. Mean SHBG was significantly higher in the older group (p<0.001).

Conclusions: A remarkably wide distribution of SHBG concentrations was observed in a clinical population of men presenting to a men's health center, among both younger and older men. Since SHBG concentrations greatly influence test results for hormones that bind to SHBG, recognition of this large interindividual variability should be considered in the clinical interpretation of these hormone results, particularly for T. Routine SHBG testing should be considered for men suspected of T deficiency.

Patient summary: Sex hormone-binding globulin (SHBG) levels vary widely among both older and younger men. This may impact the interpretation of test results for hormones that bind to SHBG, such as testosterone, since the portion that binds to SHBG is believed to not be biologically available.

Keywords: Androgens; Free testosterone; Sex hormone–binding globulin; Testosterone.