Home / Trigger atlas / Medications & treatments / Letrozole, anastrozole & tamoxifen
Medications · Updated 2026-10-30 · Editorial review in progress
Letrozole, anastrozole and tamoxifen hair loss: when it starts
Also searched as: letrozole hair lossanastrozole hair losstamoxifen hair lossaromatase inhibitor hair thinning
In 112 women with endocrine-therapy-induced alopecia, 67% of cases were attributed to aromatase inhibitors and 33% to tamoxifen; 92% were mild (grade 1) with a pattern like androgenetic alopecia, and most people report it within the first 12 months of starting treatment.
No consistent week-by-week window is published for this, so it is not on the calculator.
The timeline
| Stage | When (typically) | What's happening |
|---|---|---|
| Onset | Usually within the first 12 months | ACS: most people with hormone-therapy hair thinning report it within the first 12 months of starting treatment. [American] |
| Pattern | Thinning like pattern hair loss | 92% of 104 photographed cases were grade 1, with a pattern similar to androgenetic alopecia. [JAMA] |
| After stopping | Improvement in about 3–6 months | Cancer Research UK: improvement is usually seen 3 to 6 months after stopping hormone therapy; full growth can take over a year. [Cancer] |
Aromatase inhibitor vs tamoxifen
| Aromatase inhibitors (letrozole, anastrozole, exemestane) | Tamoxifen | |
|---|---|---|
| Share of 112 cases | 67% [JAMA] | 33% [JAMA] |
| Pattern | Like female pattern thinning [JAMA] | Like female pattern thinning [JAMA] |
| After chemo | — | Linked to slower regrowth after chemo [NPJ] |
This is a different clock from chemotherapy: chemo hair falls fast; hormone-therapy thinning creeps in over months and looks like a widening part.
Normal vs. warning signs
- Gradual widening of the part over months
- Thinning at the crown without bald patches
- Patches or smooth bald spots
- Scalp pain, redness, burning or scaling
- Loss of eyebrows, eyelashes or body hair
- Rapid, heavy shedding — look for another trigger
What may help
- Never stop or change a prescribed medicine on your own — raise hair changes with your prescriber, who can weigh them against why you take it.
- Ask your oncology team or a dermatologist about treatment options; in the 2018 study minoxidil was assessed in 46 patients.
- Take dated photos of your part line every month.
Related triggers
Hair regrowth after chemotherapy
Medical treatmentsPersistent hair loss after taxanes (docetaxel)
Starting/stopping treatmentsStarting minoxidil
Life eventsStopping birth control
Frequently asked questions
Does letrozole cause hair loss?
Yes, it can. In a 112-patient study, aromatase inhibitors such as letrozole and anastrozole accounted for 67% of endocrine-therapy hair loss cases.
When does anastrozole hair loss start?
Most people report hormone-therapy thinning within the first 12 months of starting, per the American Cancer Society.
Is tamoxifen hair loss permanent?
Cancer Research UK says it usually recovers, with improvement about 3–6 months after stopping, though some people's hair stays thinner.
Should I stop letrozole because of hair thinning?
No — never stop on your own. Hormone therapy is prescribed to reduce cancer risk; talk to your oncology team.
Sources
- JAMA Dermatology, 2018. Endocrine Therapy–Induced Alopecia in Patients With Breast Cancer (n=112)
- American Cancer Society. Hair Loss (Alopecia)
- Cancer Research UK. Hair loss, hair thinning and cancer drugs
- NPJ Breast Cancer, 2025. Clinical and genetic predictors of persistent chemotherapy-induced alopecia despite scalp cooling in breast cancer (n=123)