Serum testosterone and bioavailable testosterone correlate with age and body size in hypogonadal men treated with testosterone undecanoate (1000 mg IM--Nebido).

Objective: To investigate the loading regimen for intramuscular (IM) testosterone undecanoate (Nebido) to determine whether testosterone and bioavailable testosterone levels achieved correlate with age or body size of subjects studied.

Design: Retrospective observational study of testosterone naïve patients and patients previously treated with an alternative testosterone therapy.

Patients: 51 hypogonadal men (35, 68.