In a recent placebo-controlled study, long acting testosterone undecanoate (an ester of testosterone) improved erectile function, intercourse satisfaction, and sexual desire scores in type 2 diabetic men with severe hypogonadism, a condition in which the body doesn't produce enough testosterone. Only sexual desire improved significantly with testosterone replacement therapy in those with mild hypogonadism.

"The study's results also suggest that trials of testosterone therapy should be for a minimum of 6 months and not shorter periods as suggested by some guidelines," said Dr. Geoffrey Hackett, lead author of the BJU International study.

Article: Testosterone Undecanoate improves Sexual Function in Men with Type 2 diabetes and Severe Hypogonadism: Results from a 30 week randomized placebo controlled study, Geoffrey Hackett, Nigel Cole, Atif Saghir, Peter Jones, Richards C Strange and Sudarshan Ramachandran, Medicine & Healthcare, doi: 10.1111/bju.13516, published online 28 April 2016.