Endocrine Abstracts

A reliable form of androgen substitution therapy in terms of favorable kinetics and tolerance as well as effective restoration of androgenicity is paramount in hypogonadal men. A feasible modality is the intramuscular injection of the long-acting ester testosterone undecanoate (TU).

We report data from 183 patients (99 with primary, 70 with secondary hypogonadism and 14 with late-onset hypogonadism) aged 15–70 years (mean 37±12 years) receiving altogether 2135 intramuscular injections of 1000 mg of TU during a maximal treatment time of 11 years.

The medication was well tolerated and local irritation of the injection site was moderate and did not exceed a duration of 3 days. Serum trough levels of testosterone were generally within the low normal range, indicating sufficient substitution. Individual dosing intervals ranged from 10 to 14 weeks. In accordance, patients reported restoration of sexual functions and convenient changes in mood patterns, e.g. gain of vigor and loss of depressiveness. In contrast to short-acting testosterone esters, sensation of fluctuations in androgen concentrations was rarely reported. Hematocrit was significantly elevated under treatment but remained within the normal range, except for 13 measurements (maximal value 54.4%). PSA concentrations did not exceed 4.0 μg/l, except for one measurement (5.5 μg/l) in a case of later confirmed prostatitis. Bone density generally improved in all patients.

In summary, intramuscular injections of testosterone undecanoate represent a feasible, safe and well tolerated modality of androgen substitution in hypogonadal men of a wide age-range, also on the basis of more than one decade of experience.