What are the side effects of testosterone replacement therapy? In general, hormone replacement therapy is safe. It is associated with some side effects, including: acne or oily skin mild fluid retention stimulation of prostate tissue, with perhaps some increased urination symptoms such as decreased stream or frequency breast enlargement worsening of sleep apnea (a sleep disorder that results in frequent night time awakenings and daytime sleepiness) decreased testicular size :rofl Many of these side effects are not common. Laboratory abnormalities that can occur with hormone replacement include: changes in cholesterol concentrations increase in red cell count decrease in sperm count, producing infertility (especially in younger men)