Symptoms of low testosterone include reduced libido, erectile dysfunction, lack of initiative, increased abdominal fat, reduced muscle tone and loss of bone density. Low testosterone can also adversely affect mood and cognition. Research appearing in the Journal of Clinical Endocrinology Metabolism (November 2004;89(11):5462-8) has shown a link between type 2 diabetes and hypogonadism (low testosterone) in men. The study looked at over 100 men with type 2 diabetes and found that 33% were hypogonadal. The low testosterone levels were not necessarily linked to obesity, as about 30% of the lean patients had low testosterone.

There seems to be a link to insulin resistance and low testosterone. Another cross-sectional survey of 580 type 2 diabetic men and 69 men with type 1 diabetes that appeared in the Journal of Clinical Endocrinology Metabolism (May, 2008; Vol. 93, No. 5 1834-1840), looked at insulin resistance and low testosterone levels. Type 2 diabetes is the result of insulin resistance. Type 1 diabetics are incapable of producing insulin. The study found that 43% of the type 2 diabetics had reduced total testosterone and 57% had a reduced calculated free testosterone. Only 7% of the subjects with type 1 diabetes had low total testosterone. The calculated free testosterone levels were low in 20.3% of the subjects with type 1 diabetes.