Systemic effects of transdermal testosterone for the treatment of microphallus in children

Objectives: To elucidate the metabolic effects of topical testosterone for the treatment of microphallus in children. Methods: We administered 5% testosterone ointment to 50 prepubertal boys for the treatment of microphallus, allowing us to observe its metabolic effect on plasma concentrations of testosterone as a marker of transdermally absorbed testosterone, insulin-like growth factor (IGF)-I as a marker of growth hormone secretion status, and osteocalcin as a marker of bone metabolic turnover. Results: Transdermal application of testosterone for 30 days at a dose that affects penile growth increased mean (±SD) plasma testosterone concentrations from 7.5±5.1 to 31.0±8.2 ng/dL (pre- vs post-treatment, respectively; P<0.01). This was associated with a slight but statistically significant elevation of IGF-I concentrations (117.2±76.9 vs 154.4±81.5 ng/mL; P<0.05). No significant change in osteocalcin levels was found. Conclusions: When using testosterone ointment as a treatment for microphallus, it should be borne in mind that this application has systemic effects.