Predicting the Metabolic Syndrome According to Serum Total Testosterone, Free Testosterone Index and SHBG in Males Aged Over 20 Years: Tehran Lipid and Glucose (TLGS)

In recent years, much attention has been focused on the metabolic syndrome and its association with development of non insulin dependent diabetes mellitus (NIDDM) and cardiovascular disease. Although androgen deficiency in men is associated with obesity, whether the deficiency predisposes to, or is a consequence of the syndrome is still unclear. This study aimed at assessing the association between low levels of total testosterone, the sex hormone binding globulin (SHBG) and free testosterone index, and development of the syndrome, based on ATP III and IDF criteria. We assessed 836 men, aged ≥ 20 years, participants of the Tehran Lipid Glucose Study, at baseline and over 6.5 years follow-up, according to both definitions for occurrence of metabolic syndrome, following adjustment for confounding factors such as age, physical activity, smoking, education, fasting plasma glucose, triglycerides, serum HDL-C, waist circumference, systolic and diastolic hypertension. Using logistic regression models, the association between serum total, free testosterone index and SHBG and metabolic syndrome was investigated. After 6.5 years of follow-up, metabolic syndrome was found to have developed in 131 men and 207 men according to ATP III and IDF criteria respectively. Multiple logistic regression analysis showed an inverse relationship for total testosterone in the lower tertile concentration and serum triglycerides according to both criteria [odds ratio (OR)=1.6 95% confidence interval (CI), 1.02-2.5)]. According to ATP III criteria, adjustment of waist circumference eliminated most of the correlations between total testosterone and metabolic syndrome (OR=1.34, 95% CI (0.8-2.3), while SHBG and free testosterone index were not significantly associated with the syndrome. According to IDF criteria, statistical adjustment of waist circumference eliminated most of the correlations between total testosterone and metabolic syndrome [(OR=1.45, 95% CI (0.9-2.3)], and adjustment with triglycerides eliminated any correlation between SHBG and metabolic syndrome (OR=1.5, 95% CI (0.9-2.5). Our data do not support a predictive or causative role androgen deficiency in the development of metabolic syndrome according to ATP III and IDF definitions but do demonstrate that androgen deficiency may be consequence of the effect of poorly controlled triglycerides and increased waist circumference on, rather that a cause of, poor metabolic status.