Testosterone deficiency syndrome (TDS) is a clinical and biochemical syndrome associated with aging, characterized by symptoms suggestive of testosterone deficiency and a decrease in serum testosterone levels.

In most cases, the reason for consultation with a urologist/andrologist is erectile dysfunction or decreased libido. However, beyond these symptoms, testosterone deficiency is associated with a range of conditions that negatively affect men’s health.

Both plasma testosterone levels and those of its carrier proteins undergo significant changes associated with aging. While total testosterone and albumin levels tend to decrease, SHBG (sex hormone-binding globulin) levels increase; therefore, more plasma testosterone binds to SHBG, resulting in a decrease in free and bioavailable testosterone fractions. For this reason, levels of free and bioavailable testosterone decline with age to a greater extent than total testosterone levels. Population studies have shown that by the age of 80, men have only 50% of the testosterone levels observed in healthy 20-year-old men.

A decrease in serum testosterone levels leads, among other effects, to reduced sexual function and mood, as well as decreased bone mineral density and changes in body composition.

The main objective of testosterone replacement therapy is to restore normal physiological testosterone concentrations. The method of testosterone replacement depends on availability, safety, tolerability, efficacy, and the preferences of both the patient and the physician. Currently, injectable formulations and transdermal gels are available.