There is increasing scientific evidence that low testosterone causes sexual dysfunction, visceral obesity, hypertension, insulin resistance, and dyslipidemia. Researchers investigated the effects of administration of the long-acting testosterone undecanoate to a cohort of elderly men with sexual dysfunction for 1 year. Their plasma testosterone levels were below the lower limit of normal. At the end of the study, administration of testosterone undecanoate normalized testosterone levels but also resulted in reversal of the metabolic syndrome. Plasma cholesterol, LDL and triglycerides declined. Plasma HDL showed a parallel rise. The decline in waist circumference was significantly correlated with the fall of plasma cholesterol and LDL. After 12 months there was a modest drop in values of systolic blood pressure. There were no changes in plasma PSA levels, in glucose and hemoglobin A1c levels and liver function. It was reassuring that over a one year period of testosterone administration there were no safety concerns reported.

Saad F, Gooren L, Haider A, Yassin A. An exploratory study of the effects of 12 month administration 

of the novel long-acting testosterone undecanoate on measures of sexual function and

 the metabolic syndrome. Arch Androl. 2007 Nov-Dec;53(6):353-7.