FSH (Follicle-Stimulating Hormone)
Follicle-stimulating hormone (FSH) is produced by the pituitary gland and stimulates ovarian follicle development. FSH levels vary significantly across the menstrual cycle and are a primary marker for ovarian reserve and menopausal status.
In the follicular phase, FSH rises to stimulate egg maturation. It peaks at mid-cycle to trigger ovulation, then drops in the luteal phase. Persistently elevated FSH indicates diminished ovarian reserve or menopause.
Note: Reference ranges vary by cycle phase. Always note cycle day when interpreting results. Source: ACOG, Endocrine Society.
What It Measures
Pituitary hormone that stimulates ovarian follicle development.
Reference Ranges
| Status | Range (mIU/mL) |
|---|---|
| Optimal | 3.5–12.5 mIU/mL (follicular phase) |
| Normal | 4.7–21.5 mIU/mL (mid-cycle peak) |
| Borderline | 25.8–134.8 mIU/mL (postmenopausal) |
| Out of Range | Range varies by cycle phase — consult provider |
Range by Cycle Phase
| Cycle Phase | Reference Range |
|---|---|
| Follicular | 3.5–12.5 mIU/mL (days 1–13) |
| Ovulatory | 4.7–21.5 mIU/mL (mid-cycle peak) |
| Luteal | 1.7–7.7 mIU/mL (days 17–28) |
| Menopause | 25.8–134.8 mIU/mL |
Source: Endocrine Society, ACOG. Ranges are approximate — consult your provider.
When to test: Day 3 for baseline fertility assessment. Paired with estradiol.
Interpreting Your Results
When Values Are High
Diminished ovarian reserve, menopause, or primary ovarian insufficiency. Ovaries producing less inhibin → pituitary increases FSH.
When Values Are Low
Hypothalamic or pituitary dysfunction. May indicate hypothalamic amenorrhea from low body weight or stress.
How GATOR Tracks This
Lab Providers
Related Clinical Ratios
Related Biomarkers
This content is for informational purposes only and does not constitute medical advice. Reference ranges may vary by laboratory and individual factors. Consult a qualified healthcare provider for interpretation of your results and treatment decisions.
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