Aim: Data on the prevalence of low serum testosterone in men with type 2 diabetes mellitus (T2DM) from sub-Saharan Africa are scanty. The aim of this study was to determine the prevalence and associated risk factors of low serum testosterone in South African men with T2DM; the prevalence of androgen deficiency symptoms was also assessed.

Methods: This was a cross-sectional study in men with T2DM attending two diabetes clinic in Durban. Androgen deficiency symptoms (ADS) were assessed using the Ageing Male’s Symptom Scale (AMS) questionnaire. Serum total testosterone (TT), sex-hormone binding globulin (SHBG), leutinising hormone (LH), HbA1c, fructosamine and serum lipids were measured; free-testosterone (fT) was calculated with a standard formula. The control group included men without a history of diabetes. Low serum fT (LSFT) was defined as <180 pmol/l and low TT (LSTT) as < 12nmol/l/. 

Results: The analysis included 148 men with T2DM (Study Group) and 50 control subjects (Control Group). In the study group, majority were African (Black) (58.7%); Indians (39.2%) and Whites (2.1%) constituted the remainder. 

In the study group, mean age was 57.5±11.2 years and mean duration of diabetes 11.4±8.9 years; mean HbA1c was 8.6±1.9. Prevalence of ADS using AMS score was 74.5% while the prevalence of erectile dysfunction, loss of libido, decrease beard growth and infertility was 58.8%, 56.1%, 2.7% and 2% respectively. Mean TT, SHBG, fT and LH were within normal range (14.5±5.8 nmol/l, 40.7±20.3 nmol/l, 265.9±90.4 pmol/l and 5.3 IU/l, respectively). However, mean serum TT and fT was lower in study group than control subjects (14.5 vs. 18.5nmol/l, p <0.001 and 265.9 vs. 351.7 pmol/l, p<0.001).

The prevalence of LSTT and LSFT in the study group was 35.8% and 16.2%, respectively. Prevalence of LSFT was higher with age and BMI (Figure 1 and 2). The highest prevalence of LSFT (50%) was noted in patients with a BMI>40 kg/m2. In patients with a LSFT (n=24), 20.8% had elevated LH values, 70.8% had normal levels and 8.3% had low LH levels. 

In multivariate analysis, LSFT was significantly associated with age [OR 1.05 (95%CI 1.02-1.218), p=0.043)] and waist circumference [OR 1.033 (95%CI 0.999-1.068, p=0.059)] whilst LSTT was associated with BMI [OR 1.138 (95%CI 1.063-1.218), p<0.0001)]. There was an inverse correlation between TT and BMI (r -0.34, p<0.001) and between TT and waist circumference (r -0.35, p<0.001); fT correlated inversely with BMI, waist circumference and WHR (r -0.27, p<0.001; r -0.33, p<0.00;1 r -0.22, p<0.05). There was a low correlation between AMS scores and LSTT or LSFT. 

Conclusion: There is a high prevalence of low serum testosterone and ADS in this group of South African men with T2DM, similar to that reported in other countries. Testosterone was lower in men with T2DM compared to control subjects. There was a poor association and correlation between ADS and low testosterone. More data is required from South Africa and sub-Saharan Africa before screening can be recommended.

Prevalence of low serum testosterone in men with type 2 diabetes attending two diabetes clinics in Durban, South Africa