Prevalence of low serum testosterone levels among men with type 2 diabetes mellitus attending two outpatient diabetes clinics in KwaZulu-Natal Province, South Africa

Abstract

Background. The reported prevalence of low testosterone among men with type 2 diabetes mellitus (T2DM) is high. However, there is a dearth of information on the prevalence of androgen deficiency symptoms and low serum testosterone levels in men with T2DM from sub- Saharan Africa. Scanty data are available from Nigeria, Ghana and South Africa (SA). Objectives. To determine the prevalence of low serum testosterone and associated risk factors and the prevalence of androgen deficiency symptoms in men with T2DM. Methods. In a cross-sectional observational study, androgen deficiency symptoms in men with T2DM attending two outpatient diabetes clinics in Durban, KwaZulu-Natal Province, SA, were assessed using the Ageing Males' Symptoms Scale (AMS) questionnaire and direct enquiry. Serum total testosterone (TT), sex hormone-binding globulin (SHBG), luteinising hormone (LH), fructosamine, serum lipids and glycated haemoglobin (HbA1c) were measured and free testosterone (FT) was calculated. TT, SHBG and FT levels were measured in control subjects with no history of diabetes. Results. There were 148 men with T2DM in the study group and 50 control subjects in the control group. In the study group, the majority were black Africans (58.8%); Indians (39.2%) and whites (2.0%) constituted the remainder. The mean (standard deviation (SD)) age was 57.5 (11.2) years, the mean duration of diabetes 11.4 (8.9) years and the mean HbA1c 8.6% (1.9%). Of the study group, 85.8% had metabolic syndrome. Mean TT, SHBG and FT and median LH (interquartile range) in the study group were within normal ranges. However, mean (SD) serum TT and FT were lower in the study group than in the control subjects (14.5 (5.8) v. 18.8 (7.2) nmol/L; p<0.001 and 265.9 (90.4) v. 351.7 (127.3) pmol/L; p<0.001, respectively). The prevalence of low serum total testosterone (LSTT) and low serum free testosterone (LSFT) in the study group was 35.8% and 16.2%, respectively. The prevalence of androgen deficiency symptoms using the AMS questionnaire was 74.5% and correlated poorly with LSTT or LSFT. In multivariate analysis, LSFT was significantly associated with age (odds ratio (OR) 1.05, 95% confidence interval (CI) 1.02 - 1.218; p=0.043) and waist circumference (WC) (OR 1.033, 95% CI 0.999 - 1.068; p=0.059). LSTT was associated with body mass index (BMI) only (OR 1.138, 95% CI 1.063 - 1.218; p<0.0001). TT correlated inversely with BMI, WC and the number of metabolic syndrome criteria. FT correlated inversely with BMI, WC and WHR. Conclusions. There was a high prevalence of LSTT, LSFT and androgen deficiency symptoms in this study. Serum TT and FT were lower in men with T2DM than in control subjects. Risk factors associated with LSFT or LSTT included higher BMI and WC and older age. The AMS score was a poor predictor of low testosterone. More research is required locally before any screening policy can be recommended.