The FDA has approved two new oral formulations of testosterone undecanoate — Kyzatrex (Marius) and Tlando (Antares) — for treatment of males with a deficiency of endogenous testosterone due to conditions such as Klinefelter syndrome, orchiectomy, toxic damage from chemotherapy or alcohol, or pituitary-hypothalamic injury caused by tumors, trauma, or radiation. Jatenzo, another oral testosterone undecanoate formulation, was approved for the same indication in 2019. No testosterone products are approved for treatment of low testosterone levels due solely to aging.

Three coordinated double-blind, placebo-controlled clinical trials have evaluated the efficacy of one year of testosterone replacement therapy in improving sexual function, physical function, and vitality in a total of 790 men ≥65 years old with moderately low serum testosterone concentrations and symptoms suggesting hypoandrogenism. Sexual function improved modestly, and there appeared to be marginal benefits in some areas of physical function and vitality as well. The trials were not designed to evaluate the safety of testosterone replacement therapy.