H-36731: Finasteride in Management of Elevated Red Blood Cells

Hypogonadism is becoming an increasingly recognized clinical syndrome affecting millions of men in the United States and globally, and is characterized by symptoms including chronic fatigue, decreased libido and muscle mass, and low serum testosterone level. Treatment of hypogonadism in men typically involves treatment with exogenous testosterone.

However, exogenous testosterone therapy is not without risks, and can cause numerous side effects including high blood pressure, hyperlipidemia, and erythrocytosis, or elevated hematocrit. Adverse effects of erythrocytosis can include an increased risk of developing thromboembolism, and treatment of erythrocytosis involves therapeutic phlebotomy and testosterone dose adjustment, which can decrease the symptomatic benefits of testosterone therapy.

Aghazadeh et al.found that erythrocytosis occurring during testosterone therapy may be related to dihydrotestosterone (DHT) levels. As part of normal physiology, testosterone is converted to DHT via 5-alpha reductase (5AR). DHT is associated with various effects on the body, including stimulation of prostate growth, male pattern baldness, and others. Currently, finasteride, a 5-alpha reductase inhibitor (5ARI), is available as an FDA-approved drug used to treat DHT-related prostate growth and to prevent DHT-related baldness.

Given the positive association between DHT and the increased hematocrit seen in men being treated for hypogonadism with exogenous testosterone, finasteride's effects in preventing the synthesis of DHT may improve or even prevent erythrocytosis in men on testosterone.

The study will be a prospective randomized controlled trial of patients on injectable testosterone therapy. Subjects will be evenly distributed between the control and treatment groups. The treatment groups will receive finasteride and the control groups will not. All subjects will then be followed with blood tests to determine if there are any changes in their hematocrit, testosterone, DHT, and other blood test values.

An interim data analysis will be performed after approximately 150 men (75 treatment and 75 control) are accrued into the study and followed for at least 1 year. Rates of hematocrit elevation and erythrocytosis will be evaluated in finasteride treated and untreated men to determine whether finasteride is having an impact on erythrocytosis rates and whether any unanticipated adverse effects are occurring. Secondary outcomes, including effects on erythropoietin and hepcidin levels, will also be evaluated. Study accrual will continue if there is evidence that finasteride may decrease the incidence of erythrocytosis. The study will be stopped if unacceptable adverse events are identified or if there is no evidence suggesting that finasteride mitigates the risk of erythrocytosis.