Testosterone Concentrations In Young Patients With Diabetes Mellitus
Although it has been known for two decades that males with type 2 diabetes have low testosterone concentrations and that subjects with low testosterone concentrations are likely to develop type 2 diabetes, the issue of low testosterone concentrations has been treated as a marker associated with type 2 diabetes and features of the metabolic syndrome(1-3). These studies were based on total testosterone concentrations. The first study to attract attention towards the low testosterone concentrations as a feature of clinically relevant hypogonadism in type 2 diabetic males (age range: 28 to 80 years) was based on free testosterone concentrations(4).
Dhindsa and colleagues demonstrated that one third of males with type 2 diabetes had subnormal free testosterone concentrations and that most of these patients had TT and FT concentrations in the low normal or subnormal range. This was associated with SHBG concentrations in the low normal range. This study also demonstrated that these patients had inappropriately low LH and FSH concentrations. Thus, these patients had hypogonadotrophic hypogonadism (HH).
Total and free testosterone concentrations were also inversely related to age as expected and to BMI. However, hypogonadism was not entirely dependent upon obesity since 25% of non-obese patients(31% of lean and 21% of overweight) also had HH(4). This observation has now been confirmed by studies from the UK, Brazil, Italy and Australia(5-8). Clearly, therefore, HH occurs frequently in males with type 2 diabetes. Type 2 diabetic men with low testosterone have also been found to have a high prevalence of symptoms suggestive of hypogonadism(5). All of the above studies were based on middle aged patients.
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