I am a reproductive‑age woman taking letrozole 7.5 mg from cycle day 3‑7; my follicle‑stimulating hormone (FSH) levels were 8.7 IU/L on day 5, 12.2 IU/L on day 7, and 2.4 IU/L on day 9—are these values normal?

Understanding Your FSH Pattern During Letrozole Treatment

Your FSH fluctuations during letrozole treatment are completely expected and normal—the rise to 12.2 IU/L on cycle day 7 reflects the medication's intended mechanism of action, while the subsequent drop to 2.4 IU/L on day 9 demonstrates appropriate negative feedback as follicles develop. 1

Why These FSH Changes Occur with Letrozole

Letrozole's Mechanism Creates Predictable FSH Dynamics:

• Letrozole blocks aromatase enzyme activity, temporarily reducing estradiol production during days 3-7 of your cycle 2, 1
• This estradiol suppression removes negative feedback on your pituitary gland, causing FSH to rise naturally 1
• The FSH elevation you experienced (from 8.7 to 12.2 IU/L) is the therapeutic goal—it stimulates follicle recruitment and growth 2, 1
• Once letrozole is discontinued after day 7, developing follicles produce increasing estradiol, which then suppresses FSH through normal negative feedback 1
• Your day 9 FSH of 2.4 IU/L indicates successful follicular development with appropriate estradiol production restoring negative feedback 1

What Your Specific Pattern Indicates

Your FSH trajectory suggests optimal response to letrozole:

• The mid-treatment rise to 12.2 IU/L falls within the expected range for letrozole-stimulated cycles 1
• Studies demonstrate that FSH levels during letrozole treatment remain significantly lower than with FSH-only stimulation protocols, yet achieve comparable follicular development 1
• The subsequent drop to 2.4 IU/L by day 9 confirms that follicles responded appropriately and are producing estradiol 1
• This pattern is distinctly different from pathological FSH elevation, which would remain persistently elevated and indicate primary ovarian dysfunction 3, 4

Critical Distinction: Medication Effect vs. Ovarian Dysfunction

Your FSH pattern is medication-induced, not a sign of diminished ovarian reserve:

• Baseline day 3 FSH >10 IU/L measured before starting letrozole would suggest diminished ovarian reserve 4
• Your day 5 FSH of 8.7 IU/L (while on letrozole) and day 7 FSH of 12.2 IU/L represent the drug's intended effect, not ovarian failure 1
• Pathological FSH elevation would show persistently high levels (>10-15 IU/L) on baseline cycle day 3 testing without medication 3, 4
• The rapid decline to 2.4 IU/L proves your ovaries responded appropriately to stimulation 1

Expected Hormonal and Follicular Dynamics

Letrozole combined with your treatment protocol creates specific patterns:

• Estradiol levels remain significantly lower throughout most of the follicular phase with letrozole compared to FSH-only protocols 2, 1
• Despite lower estradiol, follicular development proceeds normally with appropriate FSH stimulation 2, 1
• Endometrial thickness may be slightly reduced during early monitoring but typically normalizes by the time of ovulation trigger 2, 1
• The number of mature follicles (>15mm) is typically lower with letrozole protocols, which reduces multiple pregnancy risk 1

What to Expect Going Forward

Your treatment response suggests good prognosis:

• The FSH pattern you experienced indicates your ovaries are responsive to stimulation 1
• Pregnancy rates with letrozole 7.5mg (5.0mg) combined with monitoring are comparable to higher-dose gonadotropin protocols 5, 6
• The lower follicular count associated with letrozole reduces the risk of multiple pregnancy and ovarian hyperstimulation 1
• If additional FSH supplementation is needed, the letrozole pre-treatment typically reduces the total gonadotropin dose required 6, 1

Common Pitfalls to Avoid

Do not misinterpret medication-induced FSH changes as ovarian failure:

• FSH measurements during active letrozole treatment cannot be used to assess baseline ovarian reserve 1
• True ovarian reserve assessment requires baseline cycle day 3 FSH measurement before starting any ovulation induction medication 4
• Single FSH measurements during stimulation cycles reflect the dynamic interplay between medication, follicular development, and feedback mechanisms—not static ovarian function 1
• The rapid FSH fluctuations you observed (8.7 → 12.2 → 2.4 IU/L) are characteristic of normal medication response, not hormonal instability 1