OBJECTIVE: Serum testosterone measurement is an integral part of the endocrine assessment
of men. Little is known about its variation in relation to migration. We examined
within a South Asian group the effect of migration to the UK on androgen levels. DESIGN:
Circulating testosterone and SHBG concentrations were measured in 97 Gujarati men
resident in India and in 79 men from the same villages of origin living in Birmingham,
UK. Free testosterone was calculated by Vermeulen's method. Insulin sensitivity (HOMA-S)
was determined from paired fasting plasma intact insulin and glucose values. RESULTS:
Circulating testosterone was significantly lower in UK Gujarati men (17.2 nmol/l [15.7-18.7])
vs. Indian Gujarati men (21.7 [20.0-23.5]) (P = 0.0002) (age-adjusted median [95%
CI]). There was no difference by migration status in circulating free testosterone.
Sex hormone binding globulin (SHBG) levels were lower in UK migrants (16.8 nmol/l
[15.5-18.1]) than in nonmigrants (21.9 nmol/l [20.5-23.3]) (P < 0.0001). Testosterone
level correlated positively with insulin sensitivity (HOMA-S) (rho 0.16, P = 0.04).
In multivariate analysis, total testosterone was independently and positively associated
with logSHBG (normalized beta (beta) = 0.29, P = 0.002) and independently and negatively
with waist circumference (beta = -0.19, P = 0.04), in a model also including height,
age, migration status, leptin and fasting insulin. CONCLUSION: Lower circulating testosterone
in UK Gujarati men and its association with markers of insulin sensitivity suggest
a profound influence of body composition change with migration on testosterone levels.
The lower SHBG in this group restores parity in free testosterone. Account should
be taken of SHBG in interpreting testosterone levels in men, as well as in women.