Prevalence and prognosis of a low serum testosterone in men with type 2 diabetes: the Fremantle Diabetes Study Phase II. (5th May 2016) - Hamilton, Emma J.
Summary: Background: Because published studies have usually involved imprecise assays and selected patients with limited additional data and follow‐up, the consequences of a low serum testosterone in diabetes are unclear. This study assessed the prevalence, associates and prognosis of a low testosterone in community‐dwelling men with type 2 diabetes. Design: Longitudinal observational study. Patients: 788 men (mean ± SD age: 65·8 ± 11·3 years) followed for 4·0 ± 1·1 years. Measurements: Serum testosterone, SHBG, erectile dysfunction (ED; Sexual Health Inventory for Men score <22), anaemia (haemoglobin <130 g/l), all‐cause mortality. Results: The mean ± SD total serum testosterone by liquid chromatography/mass spectrometry was 13·1 ± 5·9 nmol/l (30·6% <10 nmol/l). Most men with a total testosterone <10 nmol/l (67·0%) had a normal/low serum LH. Serum testosterone was independently associated with anaemia ( P < 0·001), but not ED ( P = 0·80), in logistic regression models. The optimal cut‐point (Youden Index) for anaemia was 9·8 nmol/l (sensitivity 53·6%, specificity 75·4%). During the follow‐up, 102 men (12·9%) died. There was a U‐shaped relationship between total serum testosterone quintiles and death ( P = 0·003, log rank test). The middle quintile (>11·1 to ≤13·7 nmol/l) had the lowest risk and there was a 78% increased risk for highest (>16·9 nmol/l) vs lowest (≤8·6 nmol/l) quintile in Cox proportional hazards modelling ( P = 0·036). Free serum testosterone and SHBG quintiles were not associated with death. Conclusions: These data provide some support for the general conventional serum testosterone <10 nmol/l cut‐point in identifying an increased risk of anaemia and the subsequent death in men with type 2 diabetes, but indicate that high‐normal levels are also an adverse prognostic indicator.