Total but not calculated free testosterone concentration is lowered in young healthy South Asian men
Moushmi Biswas1, David Hampton2, Atilla Turkes3, Robert Newcombe4 & Aled Rees5
Background and aim: Ethnic differences in testosterone concentrations may account for variation in the prevalence of androgen-mediated disorders amongst different racial groups. Previous reports in middle-aged subjects have either found no differences, or a lowered TT and calculated free testosterone (CFT) in South Asian (SA) compared with Caucasian men. In light of this uncertainty and to exclude any confounding influence of age we sought to determine the effect of ethnicity on TT and CFT in a young population of healthy volunteers.
Methods: Following ethical approval, healthy males (age 2040) of SA (n=67) or Caucasian (n=67) origin were recruited. Subjects were excluded if they had a fasting plasma glucose (FPG) >5.9 mmol/l, central obesity (waist circumference (wc)≥94 cm (Caucasian) or ≥90 cm (SA)) or significant other disease. FPG, albumin, SHBG, insulin and TT (mass spectrometry) were measured and CFT calculated by Vermeulens formula. Insulin resistance was assessed by HOMA-IR.
Results: Subjects were well matched for age. TT was significantly lower in SA compared with Caucasian males (16.3 nmol/l, 95%CI 9.328.6 (SA); 18.4 nmol/l, 95%CI 10.631.9 (Caucasian); P=0.01) despite a lower BMI (23.2, 95%CI 18.429.2 (SA), 24.4, 95%CI 19.430.7 (Caucasian); P=0.01) and wc (82.4 cm, 95%CI 73.292.8 (SA), 84.2 cm, 95%CI 74.894.7 (Caucasian); P=0.04). HOMA-IR was higher in SA men (1.92 (SA), 1.45 (Caucasian); P=0.006) but CFT was not different between groups (0.43 nmol/l, (SA), 0.437 (Caucasian); P=0.73). Adjusting for HOMA-IR, but not BMI or wc, partly attenuated the differences in TT between groups.
Conclusions: TT levels are lower in young SA males than their Caucasian counterparts but this is only partly explained by differences in insulin resistance. CFT may be a better assessment method of androgen status in clinical practice.