Serene woman with flowing hair in a landscape of molecules and flowers, symbolizing breast cancer and hair loss treatment

Hair Loss and Breast Cancer Treatments: What You Need to Know About Spironolactone and Finasteride

Beau Callahan in Health & Wellness November 2025 • 5 min read.

"Navigating the safety of 5a-reductase inhibitors and spironolactone during endocrine therapy for breast cancer patients: A comprehensive guide for dermatologists, oncologists, and patients."

Breast cancer is a significant health concern for women, with over 250,000 new cases diagnosed annually in the United States alone. While systemic therapies, particularly endocrine therapies (ETs), have greatly improved the life expectancy of breast cancer patients, these treatments often come with challenging side effects. One of the most distressing is alopecia, or hair loss, which affects 15-25% of women undergoing ETs.

ET-induced alopecia (EIA) manifests similarly to androgenetic alopecia, leading to diffuse hair thinning over the fronto-parietal scalp area. This hair loss can significantly impact a woman's quality of life and adherence to cancer therapies. Managing EIA and persistent chemotherapy-induced alopecia (pCIA) is challenging, with limited FDA-approved options. While topical minoxidil shows some promise, other treatments like spironolactone and finasteride, commonly used for androgenetic alopecia, warrant careful consideration.

This article explores the use of 5a-reductase inhibitors (finasteride, dutasteride) and spironolactone in breast cancer patients receiving endocrine therapies, addressing their impact on sex hormone levels, potential drug interactions, and any risks of malignancy. By providing a clear, evidence-based overview, we aim to equip patients and healthcare providers with the knowledge to make informed decisions about managing hair loss during breast cancer treatment.

Understanding How Sex Hormones Affect Hair Growth

Serene woman with flowing hair in a landscape of molecules and flowers, symbolizing breast cancer and hair loss treatment

Hormones play a vital role in hair growth. Estrogen generally promotes hair growth, while dihydrotestosterone (DHT) can transform terminal hair follicles into miniaturized ones, contributing to androgenetic alopecia. Sex hormone-binding globulin (SHBG) is crucial, as it transports testosterone and estradiol in the blood. Elevated androgens, such as testosterone and DHT, can lower SHBG production, while estrogen increases it. Only free testosterone and estradiol are active, making SHBG levels inversely proportional to the degree of female AGA.

Estrogen receptor (ER) stimulation extends the duration of the anagen phase (active growth phase) in hair follicles. Antagonizing ERs can shorten this phase, leading to premature hair follicle regression (catagen) and telogen effluvium (resting phase). Female AGA likely results from both androgen stimulation of hair follicles and a relative lack of estrogen stimulation, which explains the similarities between EIA and female AGA when treated with anti-estrogens.

Estrogen: Promotes hair growth.
Dihydrotestosterone (DHT): Contributes to hair follicle miniaturization.
Sex Hormone-Binding Globulin (SHBG): Transports testosterone and estradiol; influences the amount of free, active hormones.
Estrogen Receptors (ERs): Stimulation prolongs the hair growth phase, while antagonism shortens it.

Breast cancers can be hormone-responsive (ER and/or progesterone receptor positive), HER2-responsive, or triple-negative. Estradiol (E2) works by binding to ERs, activating cell growth. Many breast cancer cells express aromatase, which converts androgens to aromatic estrogens. Selective ER modulators (SERMs) like tamoxifen block breast cancer proliferation by binding to ERa. Aromatase inhibitors (AIs) block estrogen production in peripheral tissues, potentially increasing testosterone and DHT levels in the scalp. Fulvestrant, an estrogen antagonist, and GnRH agonists like leuprolide are also used to suppress estrogen production.

The Takeaway: Navigating Hair Loss with Confidence

Hair loss during breast cancer treatment can be a challenging experience, but understanding the potential role of medications like spironolactone and finasteride offers hope. While research is still evolving, this review provides a foundation for informed discussions with your healthcare team. Collaborating with dermatologists and oncologists is key to developing a personalized treatment plan that addresses your specific needs and ensures your safety throughout your breast cancer journey.

About this Article -

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Everything You Need To Know

How does ET-induced alopecia (EIA) manifest, and what makes its management challenging during breast cancer treatment?

Hair loss during endocrine therapy, known as ET-induced alopecia (EIA), resembles androgenetic alopecia, causing diffuse thinning on the scalp. Managing EIA and persistent chemotherapy-induced alopecia (pCIA) is difficult because there aren't many FDA-approved treatments available. Although topical minoxidil is encouraging, drugs like spironolactone and finasteride, which are frequently used to treat androgenetic alopecia, need to be carefully evaluated. They might help manage alopecia without interfering with endocrine therapies.

What roles do estrogen, dihydrotestosterone (DHT), and sex hormone-binding globulin (SHBG) play in hair growth, particularly in the context of endocrine therapy?

Estrogen generally helps hair grow, but dihydrotestosterone (DHT) can turn healthy hair follicles into smaller ones, which can lead to androgenetic alopecia. Sex hormone-binding globulin (SHBG) is very important because it moves testosterone and estradiol in the blood. Higher levels of androgens, like testosterone and DHT, can lower SHBG production, but estrogen raises it. Only free testosterone and estradiol are active, therefore SHBG levels are inversely related to how bad female AGA is. Estrogen receptor (ER) stimulation also makes the anagen phase (active growth phase) of hair follicles last longer. Blocking ERs can shorten this phase, causing hair follicles to regress too soon (catagen) and telogen effluvium (resting phase).

How do selective ER modulators (SERMs) and aromatase inhibitors (AIs) affect estrogen levels and hair growth in breast cancer patients?

Selective ER modulators (SERMs) such as tamoxifen work by binding to ERa, which stops breast cancer cells from growing. Aromatase inhibitors (AIs) prevent estrogen from being produced in peripheral tissues, which may raise testosterone and DHT levels in the scalp. Additionally, fulvestrant, an estrogen antagonist, and GnRH agonists such as leuprolide are used to lower estrogen production.

Why are spironolactone and finasteride being considered for hair loss during breast cancer treatment, and what precautions should be taken?

Spironolactone and finasteride are considered because of their potential to manage hair loss during breast cancer treatment, but their use requires careful evaluation. Spironolactone functions primarily as an antiandrogen, which means it blocks the effects of androgens like DHT, which contribute to hair follicle miniaturization. Finasteride is a 5a-reductase inhibitor, which means it stops testosterone from being converted into DHT. Both drugs are used to treat androgenetic alopecia because they can lower androgen levels in the scalp. Before using spironolactone or finasteride while receiving endocrine therapy, it's important to speak with oncologists and dermatologists. They can offer tailored advice depending on the patient's medical history, hormone receptor status, and any potential drug interactions.

What are the potential implications of using finasteride, dutasteride, and spironolactone in breast cancer patients undergoing endocrine therapies?

The use of finasteride, dutasteride, and spironolactone in breast cancer patients on endocrine therapies requires careful consideration of their effects on sex hormone levels, potential drug interactions, and any risks of malignancy. While these medications may help with hair loss by reducing the effects of androgens or blocking their production, they could also interfere with the effectiveness of endocrine therapies. For instance, altering estrogen levels could affect how well hormone-responsive breast cancer cells respond to treatment. Therefore, healthcare providers need to carefully weigh the benefits and risks of using these drugs, keeping in mind the patient's overall health and cancer treatment strategy. Further research is needed to fully understand the long-term effects of these medications on breast cancer outcomes.