LEARN: Testosterone and the breasts
Testosterone, Breast Symptoms, and Breast Cancer: What We Know (and What We’re Still Learning)
Testosterone in women’s health often raises questions, particularly when breast pain, breast lumps, or breast cancer risk are part of the conversation. The reality is more nuanced than the fear-driven narratives many people encounter.
My approach in clinical practice
• I don’t prescribe testosterone to patients who have chosen not to use menopausal hormone therapy (MHT) specifically because of breast cancer risk
• When patients using testosterone report breast pain or new breast lumps, these are assessed appropriately, but unlikely to be secondary to the testosterone. This generally does result in a timely referral
• I don’t recommend extra breast screening or heightened breast surveillance simply because a patient is using testosterone (or even MHT)
Breast changes in perimenopause are common, and reassurance comes from assessment and understanding - not alarm.
How testosterone affects breast tissue
Testosterone behaves differently from estrogen in breast tissue. Research suggests it has anti-proliferative effects, meaning it tends to limit excessive breast cell growth rather than stimulate it.
Observational studies, including work by Glaser and Dimitrakakis (2013) , have shown lower rates of breast cancer in women treated with testosterone. While this doesn’t prove protection, it challenges the assumption that testosterone increases breast cancer risk.
A common concern is that testosterone can convert to estrogen via aromatisation. However, clinical data show that aromatisation can be prevented when needed, and testosterone has been used safely, even in breast cancer survivors, without increasing estrogen exposure.
Why testosterone matters for some women
Around h alf of a woman’s testosterone is produced by the ovaries, so levels often fall significantly after ovary removal and during midlife. Low testosterone can affect energy, mood, libido, musculoskeletal health, and overall wellbeing.
For some women, testosterone therapy is about restoring physiological balance, not adding excess hormone.
Rethinking hormones and breast cancer risk
Hormonal effects on breast tissue are not straightforward. From a biological perspective:
• Androgens inhibit breast development, independent of genetic sex
• Androgen excess suppresses breast tissue growth, even when estrogen levels are adequate
• Androgen use in female athletes and transmasculine individuals is associated with breast atrophy, not proliferation
These observations suggest the relationship between hormones and breast cancer risk is more complex than often presented.
Balance matters: estrogen, testosterone, and metabolism
One theory for why oral estrogen may increase breast cancer risk involves disrupting the estrogen–androgen balance. Oral estrogen raises sex hormone–binding globulin (SHBG), which binds free testosterone and reduces androgen activity in breast tissue. This may shift the balance toward estrogen dominance.
Conditions like PCOS and obesity further highlight this complexity. PCOS is linked to higher androgens and increased breast cancer risk, largely driven by metabolic factors such as insulin resistance and adiposity. In contrast, obesity without PCOS is often associated with lower testosterone levels due to increased aromatisation (and increased rates of cancer, and breast cancer).
The take-home message
Testosterone and breast health is not a black-and-white issue.
• Testosterone is not automatically harmful to breast tissue
• Breast symptoms in perimenopause are common and usually benign
• Testosterone alone does not justify increased breast screening
• Research is limited partly because female testosterone levels are difficult to measure
This is an evolving area of women’s health. Rather than fear, it deserves curiosity, careful practice, and optimism about what future research will bring.
References:
Glynne S, Simon J, Branson A, Payne S, Newson L, Manyonda I, Cleator S, Douek M, Usiskin S, Tobias JS, Vaidya JS. Menopausal hormone therapy for breast cancer patients: what is the current evidence? Menopause. 2026 Jan 1;33(1):88-117. doi: 10.1097/GME.0000000000002627. PMID: 41025376; PMCID: PMC12727074.
Glaser RL, Dimitrakakis C. Reduced breast cancer incidence in women treated with subcutaneous testosterone, or testosterone with anastrozole: a prospective, observational study. Maturitas. 2013 Dec;76(4):342-9. doi: 10.1016/j.maturitas.2013.08.002. Epub 2013 Sep 10. PMID: 24028858.
Dimitrakakis C, Zhou J, Bondy CA. Androgens and mammary growth and neoplasia. Fertil Steril. 2002 Apr;77 Suppl 4:S26-33. doi: 10.1016/s0015-0282(02)02979-5. PMID: 12007899.
