Encyclopedia · drug with hair side effects
Breast cancer endocrine therapy (tamoxifen, aromatase inhibitors)
Anti-estrogen pills taken for years after breast cancer can cause female pattern-type thinning, and in one uncontrolled series topical minoxidil helped 80% of those assessed.
What it is
Prescription drugs that block estrogen's action (tamoxifen) or its production (aromatase inhibitors) to prevent breast cancer recurrence, usually taken for 5-10 years.
How it works
Estrogen helps keep follicles in the growth phase and balances androgens. Lowering or blocking it can reveal pattern-type thinning, which matched the pattern authors saw: similar to androgenetic-type. Freites-Martinez 2018
What the studies show
- In 112 women seen at a cancer-centre dermatology service, 67% of cases were attributed to aromatase inhibitors and 33% to tamoxifen. Of those graded, 92% had grade 1 (mild) severity, and quality of life was affected mainly emotionally. Freites-Martinez 2018
- Of 46 assessed on topical minoxidil, 37 (80%) improved moderately or significantly by single-blinded photo review, with no control group. Freites-Martinez 2018
- Only patients referred with alopecia were included, so this study cannot give an incidence.
How it's used in studies
Topical minoxidil as per the clinic; doses were not described in the abstract.
Side effects and safety
Do not stop cancer endocrine therapy because of thinning without the oncology team, since the drug may protect survival. For topical minoxidil see minoxidil.
Bottom line
Real, usually mild and possibly treatable, based on one uncontrolled series. It supports counselling before therapy. Discuss with a doctor.
Fun facts
- A drug that lowers estrogen produces pattern-type thinning, a clue that hair is sensitive to the estrogen and androgen balance.
Studies 1
Freites-Martinez A et al. Endocrine therapy-induced alopecia in patients with breast cancer. JAMA Dermatol. 2018
Result: 67% on aromatase inhibitors, 33% on tamoxifen; 92% of graded patients had grade 1; topical minoxidil improved 37 of 46 (80%), uncontrolled.
Read the study ↗Related
- MinoxidilThe most widely used hair-growth treatment, available as a cheap over-the-counter lotion or foam and as a prescription tablet, with a mechanism that is still only partly understood.
- Androgenetic alopecia (male and female pattern hair loss)The most common cause of hair loss is an inherited, slowly progressive shrinking of scalp follicles; it cannot be cured, but finasteride, minoxidil and transplants slow, partly reverse or camouflage it.
- Drug-induced hair changesMedicines can thin hair, regrow it curly, darken or whiten it, or lengthen lashes; this table sorts the best-known links by how strong the evidence is.
- CDK4/6 inhibitors (palbociclib, ribociclib, abemaciclib)Breast-cancer pills that cause a thinning pattern similar to androgenetic alopecia, concentrated at the crown, with a slightly weaker response to minoxidil than with hormone therapy alone.