Serum testosterone levels in male hypogonadism: Why and when to check—A review

AIM Although "late onset hypogonadism", a condition that includes low testosterone and symptoms, is common in men over the age of 40 years, diagnosis is not clear cut amongst non-specialists. It is the aim of this review to provide an up to date picture of how this state should be diagnosed and managed. METHODS We aim to describe how primary and secondary hypogonadism should be excluded before the diagnosis of late onset hypogonadism is reached. As laboratory testosterone measurements are essential the current pitfalls such as inappropriate sample collection and the use of population derived reference ranges are expanded. We review current evidence to determine associations between late onset hypogonadism and morbidity/mortality and benefits following testosterone replacement therapy. RESULTS A review of the current evidence shows that late onset hypogonadism is associated with a worse metabolic state and increased mortality. Longitudinal studies have suggested that significant reductions in both symptoms and mortality are seen, especially in patients with type 2 diabetes. DISCUSSION This review highlights the importance of diagnosing late onset hypogonadism due to its association with morbidity/mortality and benefits following testosterone replacement. Thus, after making recommendations to ensure correct diagnosis we speculate whether the time has come to move away from population derived testosterone levels towards evidence based action limits.