Letrozole (Letrozole (Femara))
A third-generation aromatase inhibitor used off-label as first-line ovulation induction in PCOS. Superior to clomiphene for female fertility due to less anti-estrogenic effect on endometrium. Also used in men to control estradiol on TRT.
How it works
Reversibly inhibits aromatase (CYP19A1), blocking conversion of androgens to estrogens. In women, transient estrogen reduction triggers hypothalamic GnRH release for FSH surge. In men, reduces estradiol while maintaining testosterone.
Key facts
- Molecular weight: 285.30 Da
- Half-life: ~2 days
- Bioavailability: ~100% oral
- Storage: Room temperature.
Dosing overview
- Typical dose: 2.5-7.5 mg (women, day 3-7); 0.5-2.5 mg (men, 2-3x/week)
- Frequency: Cyclic (women) or 2-3x weekly (men)
- Duration: Per cycle (women); ongoing (men)
- Route: Oral tablet
Reported benefits
- Ovulation induction (PCOS)
- Higher live birth rates than clomiphene
- No anti-estrogenic endometrial thinning
- Estradiol control in men
- Lower multiple pregnancy rate
Possible side effects
- Hot flashes
- Joint pain
- Headache
- Fatigue
- Bone density concern (long-term)
- Mood changes
Research
- NEJM: Letrozole vs clomiphene for PCOS (2014): Letrozole produced significantly higher ovulation (61.7% vs 48.3%), pregnancy (27.5% vs 19.1%), and live birth rates (18.7% vs 9.4%) in PCOS women.
- Letrozole for male estradiol management (2020): 1.25mg 3x/week reduced estradiol from 52 to 24 pg/mL while maintaining testosterone levels in hypogonadal men on TRT.
Compare Letrozole
Community discussions about Letrozole
- HCG + Letrozole combo for TRT‑induced estrogen spikes – need timing tips - 4 comments
- Recent letrozole trial in men on TRT – what I think - 4 comments
- Noticed joint aches after a week on low‑dose letrozole – anyone else? - 4 comments
- Anyone tried letrozole for estrogen control alongside other compounds? - 6 comments
- Ask the community about Letrozole
Research and educational reference only. Not medical advice.