The Effects of Aromatase Inhibition and Testosterone Replacement in Sex Steroids, Pituitary Hormones, Markers of Bone Turnover, Muscle Strength, and Cognition in Older Men

Background: Men≥65 years often produce lower levels of testosterone, meaning there is less testosterone circulating to the tissues of the body. This is associated with negative effects on muscle strength, bone density, sexual function, mood, and the ability to think to the best of one's ability. Testosterone replacement therapy often involves injections, patches, or gels that help to raise circulating testosterone levels, but these therapies often have side effects because they lead to imbalance of other hormones. Researchers have been studying the effectiveness of anastrozole, a drug that can lower estrogen levels while simultaneously increasing testosterone levels, as a treatment for the negative effects of decreased circulating testosterone levels that occur naturally with aging. Objectives: To evaluate whether anastrozole is as effective as testosterone gel in improving bone and muscle strength, hormone levels, and brain function in men over 65 years of age. Eligibility: Healthy men at least 65 years of age who have low levels of testosterone. Design: The study involves six study visits over a total of 12 months: screening, baseline, 6 weeks, 3 months, 6 months, and 12 months. All participants will receive calcium and vitamin D supplements to take daily, and will be randomized to one of three groups:Testosterone gel and placebo tablet, Anastrozole tablet and placebo gel, Placebo tablet and gel. Participants will have the following tests at each specified visit:Screening: Blood tests and rectal ultrasound to evaluate the prostate;Baseline: Blood and urine tests; growth hormone levels, muscle strength, bone density, and balance evaluation; imaging studies; cognitive testing; and questionnaires on quality of life, sexual function, depression, and urinary symptoms;Six weeks: Blood tests and dose adjustment of the gel or tablet;Three months: Blood and urine tests; growth hormone, muscle strength, bone density, and balance evaluation; and questionnaires on quality of life, sexual function, depression, and urinary symptoms;Six months: Blood and urine tests; muscle strength, bone density, and balance evaluation; cognitive testing; and questionnaires on quality of life, sexual function, depression, and urinary symptoms;Twelve months: Blood and urine tests; rectal ultrasound; muscle strength, bone density, and balance evaluation; imaging studies; cognitive testing; and questionnaires on quality of life, sexual function, depression, and urinary symptoms.