What is the appropriate dosing of Anastrozole (Arimidex) for men with hypogonadism on Testosterone (T) therapy?

From the Guidelines

Anastrozole dosing for men on testosterone therapy should be individualized, but a common starting dose is 0.5 mg once weekly, with adjustments based on follow-up blood tests measuring estradiol levels. The goal of anastrozole therapy in this context is to manage estrogen-related side effects such as gynecomastia, water retention, or mood swings by inhibiting the aromatase enzyme that converts testosterone to estrogen 1. It is crucial to use the lowest effective dose for the shortest necessary duration to minimize potential side effects, including joint pain, reduced bone mineral density with long-term use, and lipid profile changes. Regular monitoring of estradiol levels is essential, typically every 2-3 months initially and then every 6-12 months once stable, with the goal of maintaining estradiol between 20-30 pg/mL 1.

Key considerations in the management of testosterone therapy and the use of anastrozole include:

• Adjusting testosterone therapy dosing to achieve a total testosterone level in the middle tertile of the normal reference range 1
• Using the minimal dosing necessary to drive testosterone levels to the normal physiologic range of 450-600 ng/dL 1
• Stopping testosterone therapy if patients do not experience symptomatic relief after reaching the specified target testosterone levels or remain testosterone deficient in the setting of symptom/sign improvement 1
• Being aware of the potential benefits and risks of anastrozole, including its effects on bone health, cognitive function, and cardiovascular health in men 1

In clinical practice, the decision to use anastrozole in men on testosterone therapy should be based on a thorough evaluation of the individual's symptoms, testosterone and estradiol levels, and potential risks and benefits. The most recent and highest quality evidence should guide this decision, with a focus on minimizing harm and optimizing outcomes in terms of morbidity, mortality, and quality of life.

From the Research

Anastrozole Dosing for Men on Testosterone

• The dosing of anastrozole for men on testosterone therapy is typically based on the management of elevated estradiol levels 2.
• A study published in 2021 found that men with elevated estradiol levels (>60 pg/mL) or symptoms with levels between 40-60 pg/mL were started on anastrozole 0.5 mg 3 times a week 2.
• The study showed that anastrozole was effective in reducing estradiol levels, with a median decrease from 65 pg/mL to 22 pg/mL 2.
• Another study published in 2015 found that high estradiol levels were common in men undergoing injectable testosterone therapy, and that aromatase inhibitors such as anastrozole were used to treat symptoms of hyperestrogenism 3.

Considerations for Anastrozole Use

• The use of anastrozole in men on testosterone therapy should be individualized and based on symptoms and estradiol levels 2.
• Aromatase inhibitors such as anastrozole may not be necessary for all men on testosterone therapy, and their use should be carefully considered 4.
• The long-term safety and efficacy of anastrozole in men on testosterone therapy are not well established, and further research is needed 5, 6.

Alternative Therapies

• Selective estrogen receptor modulators (SERMs) may be an alternative to aromatase inhibitors such as anastrozole for the treatment of functional hypogonadism 6.
• However, the use of SERMs in this context is not well established, and further research is needed to evaluate their efficacy and safety 6.