From the Guidelines
Taking testosterone without anastrozole can lead to increased estrogen levels, potentially causing unwanted side effects such as gynecomastia, water retention, mood swings, and decreased libido, as evidenced by the lack of association with increased risk for prostate cancer in a study published in the Annals of Internal Medicine 1. When testosterone is administered, some of it naturally converts to estrogen through a process called aromatization. Without anastrozole, an aromatase inhibitor that blocks this conversion, men may experience estrogen-related side effects.
- The risk and severity of these side effects depend on individual factors like dosage, duration of testosterone use, age, body composition, and genetic predisposition to aromatization.
- Some men may tolerate testosterone without anastrozole with minimal issues, while others may experience significant side effects.
- Regular blood work to monitor estrogen levels is essential when using testosterone, and anastrozole should be added to the regimen if estrogen levels become elevated beyond the normal range, as suggested by the analysis of data from 38 RCTs that found little to no effect on physical functioning, depressive symptoms, energy and vitality, and cognition 1. The study published in the Annals of Internal Medicine 1 found that intramuscular or transdermal testosterone therapy resulted in small improvements in sexual functioning and quality of life, but had little to no effect on other outcomes, and the evidence for most outcomes was of low or moderate certainty.
- Typical anastrozole dosing when needed ranges from 0.25mg to 1mg taken 1-2 times weekly, adjusted based on blood test results.
- It is crucial to prioritize patient-centered outcomes over intermediate measures, such as body composition or metabolic variables, as done in the study 1.
From the Research
Effects of Testosterone Without Anastrozole
The effects of taking testosterone without anastrozole, an aromatase inhibitor, can be significant. Testosterone replacement therapy (TRT) is commonly used to treat hypogonadism in men, but it can lead to elevated estradiol levels, which may cause adverse effects such as gynecomastia and infertility 2, 3, 4, 5.
Adverse Effects
Without anastrozole, testosterone therapy may result in:
- Elevated estradiol levels, leading to gynecomastia and other feminizing effects 4
- Increased risk of infertility due to high estradiol levels 5
- Potential cardiovascular risks, although the evidence is mixed 6
- Testicular atrophy and erythropoiesis 3
Hormonal Changes
Studies have shown that testosterone therapy without anastrozole can lead to:
- Increased total and free testosterone levels, but also elevated estradiol levels 2, 3
- Suppression of gonadotropin levels, which can affect fertility 2
- Changes in sex hormone binding globulin, luteinizing hormone, and follicle-stimulating hormone levels 2, 3
Importance of Anastrozole
Anastrozole is used to control estradiol levels and prevent adverse effects associated with elevated estradiol. The use of anastrozole with testosterone therapy has been shown to: