Endocrine Abstracts

Background: Testosterone substitution with favourable kinetics and tolerance is important for hypogonadal men. Intramuscular injections of long-acting testosterone undecanoate (TU) offer a convenient modality.

Methods: We report data from 281 patients (134 with primary, 88 with secondary hypogonadism and 59 with late-onset (‘mixed’ or ‘metabolic’) hypogonadism aged 15 to 72 years (mean 40±13 years) receiving altogether 4913 intramuscular injections of 1000 mg of TU during a maximal treatment time of 13.5 years, overall corresponding to 1069 treatment years.

Components of the metabolic syndrome were assessed in 216 men receiving 2864 injections.

Results: Trough levels of testosterone were generally within the low normal range, indicating sufficient substitution. Individual dosing intervals ranged from 10 to 14 weeks. The proportion of men fulfilling the new joint consensus criteria of the International Diabetes Federation and the National Cholesterol Education Program for definition of the Metabolic Syndrome decreased from initially 87 to 52% within 2 years (χ² for trend: P<0.001). Especially waist circumference decreased from 112.0±10.3 to 96.4±9.1 cm (P<0.001) within a year (body mass index from 30.4±5.1 to 28.6±3.8 cm (P=0.001)). Lipoprotein subfractions, blood pressure and fasting glucose levels improved in a similarly meaningful manner. Hematocrit was significantly elevated under treatment but remained within the normal range, except for occasional measurements (maximal value 56.3%).

Conclusion: Injections of testosterone undecanoate represent a feasible, safe and well tolerated modality of androgen substitution in hypogonadal men of a wide age-range, substantiated by more than one decade of experience, facilitating a decrement of metabolic/cardiovascular risk factors.