Can testosterone level be a good predictor of late-onset hypogonadism?

Androgens are essential for the development and growth of the genitalia. They regulate the erectile physiology by multiple mechanisms. Several studies have examined associations among sex hormones' serum levels, erectile function and sex drive. We sought to identify a protocol for using testosterone in men with erectile dysfunction and late-onset hypogonadism (LOH). During a 16-month period, men with erectile dysfunction who presented to the andrology clinic were selected. They underwent a complete physical examination and filled out the International Index of Erectile Function-5 questionnaire. Serum luteinising hormone (LH) and testosterone levels were evaluated. Patients received a single intramuscular injection of 250 mg testosterone. Thereafter, serum levels of LH and testosterone were measured 3 weeks later. The mean age was 53 years old. After treating patients with testosterone, 45 (94%) showed improvement in LOH symptoms including libido, loss of energy, irritability and quality of life. The mean International Index of Erectile Function was 9 and 13.1, prior to and after treatment respectively. Mean serum testosterone levels before and after treatment were 4.2 and 4.1 ng ml(-1) respectively (P = 0.849). Mean serum LH revealed a significant decrease after the study (P = 0.004) (6.12 and 5.1 ng ml(-1) , before and after the study respectively). Our findings suggested that testosterone replacement therapy improves libido and LOH symptoms in individuals with almost normal or lower limit normal value of serum testosterone levels.