EndocrinologyEndocrinology

Follicular Stimulating Hormone (FSH)

Normal Range
Male: 1.5-12.4 mIU/mL; Female: Follicular 3.5-12.5, Ovulatory 4.7-21.5, Luteal 1.7-7.7, Postmenopausal 25.8-134.8 mIU/mL
Sample Type
Serum
Fasting
No
Unit
mIU/mL

Function

Follicle-Stimulating Hormone (FSH) is a gonadotropin produced by the anterior pituitary gland. In women, FSH stimulates the growth and recruitment of immature ovarian follicles in the ovary. In men, FSH acts on the Sertoli cells of the testes to stimulate spermatogenesis (sperm production).

Why it is Ordered

FSH testing is used to evaluate fertility issues, irregular menstrual cycles, and pituitary gland disorders. In women, it is a primary marker used to confirm the onset of menopause or to diagnose Polycystic Ovary Syndrome (PCOS). In men, it is used to investigate low sperm counts or testicular failure.

Associated Conditions

  • Menopause: Characterized by very high FSH levels as the body tries to stimulate non-responsive ovaries.
  • Polycystic Ovary Syndrome (PCOS): Often shows an abnormal LH to FSH ratio.
  • Primary Ovarian Insufficiency (POI): High FSH in women under 40.
  • Hypopituitarism: Low FSH levels resulting in secondary infertility.
  • Klinefelter Syndrome: High FSH levels in males due to testicular failure.

Summary

FSH is a cornerstone of reproductive endocrinology, acting as a messenger between the brain and the reproductive organs to ensure proper gamete development.

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Interactive
mIU/mL

Enter your lab result to see where you stand compared to the standard reference range.

Why Context Matters

FSH levels fluctuate wildly during the menstrual cycle. A single measurement taken on the 'wrong' day can be misleading; it is typically measured on Day 3 of the cycle for fertility assessments. Additionally, biotin supplements and high stress can interfere with the immunoassay results.

Lab ranges are statistical averages, not biological laws. "Normal" for a 20-year-old male isn't normal for a 60-year-old female.

Clinical References

Source-of-truth databases and clinical guidelines for Follicular Stimulating Hormone (FSH):

Research & Guidelines

Related Indicators

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DR

Medically Reviewed by Dr. Binoy Babu, MBBS

Board Certified Doctor • 10+ Years Clinical Experience

Dr. Babu is a practicing physician dedicated to empowering patients with clear, actionable medical information. He founded 2opi to bridge the gap between complex lab reports and patient understanding, ensuring everyone has access to a reliable second opinion.

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