From the Research
The target progesterone level during ovulation induction with letrozole is typically above 3 ng/mL (or >10 nmol/L) in the mid-luteal phase, measured approximately 7 days after ovulation, as indicated by the most recent study 1.
Key Points to Consider
- The standard letrozole protocol involves 2.5-7.5 mg daily for 5 days, typically starting on cycle days 3-5, with 5 mg being the most common starting dose.
- Progesterone levels should be checked about one week after the expected ovulation date, which is typically 5-10 days after the last letrozole dose.
- If progesterone levels are below 3 ng/mL, it may indicate that ovulation did not occur or that luteal phase deficiency exists, and the letrozole dose may need to be increased in subsequent cycles, or additional medications like human chorionic gonadotropin (hCG) trigger shots might be considered.
- Letrozole works by temporarily inhibiting estrogen production, which increases follicle-stimulating hormone (FSH) release from the pituitary gland, stimulating follicular development and subsequent ovulation, ultimately resulting in progesterone production by the corpus luteum if ovulation is successful.
Relevant Studies
- A study published in 2021 found that letrozole was associated with significantly higher clinical pregnancy and live birth rates compared to clomiphene in treatment-naïve infertile women with PCOS 2.
- Another study published in 2011 found that there was no significant difference in ovulation rates between women treated with 5 mg or 7.5 mg of letrozole per day 3.
- A 2014 study found that letrozole ovulation induction was an effective option in endometrial preparation for frozen-thawed embryo transfer, with higher clinical pregnancy and live birth rates compared to hormone replacement therapy 4.
- A 2020 study found that letrozole was effective in inducing ovulation in women with PCOS, with a clinical pregnancy rate of 22.5% 5.
- The most recent study published in 2023 found that ovarian response can be predicted in women with PCOS who have ovulation induction with letrozole, with higher follicle development in women with lower FSH, androgen, and AMH values 1.