From the FDA Drug Label
Monitor serum testosterone, prostate specific antigen (PSA), hemoglobin, hematocrit, liver function tests and lipid concentrations periodically (5.1,5.3,5.9,5.13) In addition to PSA levels, the following laboratory values should be monitored while on transdermal testosterone therapy:
- Hemoglobin
- Hematocrit
- Liver function tests
- Lipid concentrations
- Serum testosterone 1
From the Research
In addition to PSA levels, hematocrit should be monitored in a 60-year-old male starting transdermal testosterone therapy. Baseline hematocrit should be measured before initiating treatment, followed by evaluation at 3-6 months after starting therapy, and then annually thereafter. Testosterone therapy commonly increases red blood cell production, which can lead to erythrocytosis (elevated hematocrit) 2. This is a dose-dependent effect that occurs because testosterone stimulates erythropoiesis in the bone marrow. If hematocrit rises above 54%, testosterone therapy should be temporarily discontinued or the dose reduced until the value normalizes. Persistent elevations may require therapeutic phlebotomy or alternative testosterone formulations. Other parameters that should be monitored include complete blood count, lipid profile, and liver function tests, but hematocrit is particularly important due to the increased risk of thrombotic events associated with erythrocytosis in older men receiving testosterone replacement 2. Some studies have shown that the risk of polycythemia varies with different formulations of testosterone therapy, with transdermal testosterone having a lower risk compared to intramuscular testosterone enantate 3. However, the most recent and highest quality study suggests that developing polycythemia while on testosterone therapy is an independent risk factor for major adverse cardiovascular events and venous thromboembolism in the first year of therapy 2. Therefore, monitoring hematocrit levels is crucial in patients receiving testosterone replacement therapy. Key points to consider when monitoring hematocrit levels include:
- Baseline measurement before initiating treatment
- Evaluation at 3-6 months after starting therapy
- Annual monitoring thereafter
- Discontinuation or dose reduction of testosterone therapy if hematocrit rises above 54%
- Consideration of alternative testosterone formulations or therapeutic phlebotomy for persistent elevations.