Objectives: Testosterone has a spectrum of effects on the male organism. This review attempts to determine, from published studies, the time-course of the effects induced by testosterone replacement therapy from their first manifestation until maximum effects are attained.
Design: Studies in PubMed on testosterone replacement so far providing information on time course.
Results: Effects on sexual interest appear after 3 weeks plateauing at 6 weeks, no further increments beyond. Changes in erections/ejaculations may require up to 6 months. Effects on quality of life manifest within 3-4 weeks, but maximum benefits take longer. Effects on depressive mood appear after 3-6 weeks with a maximum after 18-30 weeks. First effects on erythropoiesis (increased red blood cells) after 3 months, peaking at 9-12 months. Prostate specific antigen and volume rise, marginally, plateauing at 12 months; further increase related to aging rather than therapy. Effects on lipids appear after 4 weeks, maximal after 6-12 months. Insulin sensitivity may improve within few days, but effects on glycemic control become evident only after 3-12 months. Changes in fat mass, lean body mass and muscle strength occur within 12-16 weeks, stabilize at 6-12 months, but marginally continue to improve over years. Effects on inflammation occur within 3 to 12 weeks. Effects on bone detectable after 6 months but continue at least for 3 years.
Conclusion: the time-course of the spectrum of effects of testosterone shows considerable variation, probably related to pharmacodynamics of the testosterone preparation. Genomic and non-genomic effects, androgen receptor polymorphism and intracellular steroid metabolism further contribute to such diversity.
