Endocrine Abstracts

Conventional intramuscular preparations of testosterone esters are associated with wide fluctuations in serum testosterone (T) levels following administration, even when a lower dose (100 mg) is injected every 7–10 days, let alone 250 mg every 2–3 weeks. Depot Testosterone undecanoate [TU -Nebido] is a newly available option for androgen replacement. The possibility of achieving stable therapeutic serum T levels over a period of months is its principal attraction. Data from Germany suggest that, after adequate loading, patients can be maintained on injections spaced >12 weeks apart.

We report our initial experience with use of TU in a cohort of 20 men with organic severe hypogonadism (eg. hypopituitary, Kallmann’s, Klinefelter’s, or survivors of childhood cancer – baseline 9 am serum T at original diagnosis 0–5.0 nmol/L), who received TU injections for up to 9 months. All were transferred from other forms of T replacement and treatment was initiated with two injections of TU 1000 mg given 6-weeks apart (loading dose), followed by 1000 mg initially every 12 weeks. Following the first injection, serum T levels were measured prior to their next loading injection at 6 weeks and before every subsequent injection.

The medication was well-tolerated and no significant local irritation was reported. Individual dosing intervals ranged from 12–14 weeks. Serum total T levels prior to the second loading dose at 6 weeks was 14.4±1.4 nmol/L and serum free T levels were 261±21.5 pmol/L. Serum total T levels prior to the 3rd injection was 19.5±1.8 nmol/L, with serum free T levels 354±58.8 pmol/L. Dosing intervals were increased as appropriate and T levels prior to subsequent injections were all within the normal range, indicating physiological T replacement. All patients reported high levels of satisfaction, confirming that TU (Nebido) is a useful and well-tolerated form of replacement therapy even in men with near-total deficiency of endogenous T secretion.