Follicle stimulating hormone (FSH)

On this page

1. What is FSH?
2. Where is FSH produced?
3. Function of FSH
4. Normal FSH levels
5. FSH levels by age
6. Causes of high FSH
7. Causes of low FSH
8. FSH in men
9. When and how to test FSH
10. FSH in traditional Chinese medicine
11. Acupuncture and FSH
12. Chinese herbal medicine and FSH
13. Diet, supplements and lifestyle
14. Related pages

1. What is FSH?

Follicle stimulating hormone (FSH) is a glycoprotein hormone produced by the anterior pituitary gland in response to gonadotrophin-releasing hormone (GnRH) from the hypothalamus. FSH is one of the most important fertility hormones in both women and men. In women, FSH stimulates the ovaries to grow and mature follicles, each of which contains an egg; in men, FSH supports the production of sperm in the testes.

FSH levels rise and fall throughout the menstrual cycle, peaking briefly at the start of each cycle to stimulate a cohort of follicles to begin growing. As one follicle becomes dominant and produces increasing amounts of oestradiol, the rising oestradiol provides negative feedback on the pituitary and FSH falls again. Understanding this rhythm is key to interpreting FSH levels accurately.

Reference ranges vary from country to country and between laboratories. The values listed here are general guides — always interpret your own result against the reference range provided by the laboratory that performed your test.

If you have already been told that your FSH is elevated, see my dedicated clinical page on high FSH level, which covers symptoms, causes, age-related ranges, and how I treat high FSH naturally with acupuncture, Chinese herbal medicine, supplements and lifestyle changes at my clinic in Wokingham, Berkshire.

2. Where is FSH produced?

FSH is produced by gonadotroph cells in the anterior pituitary gland, a small gland at the base of the brain. The pituitary releases FSH after receiving GnRH signals from the hypothalamus. FSH then travels through the bloodstream to act on the ovaries (in women) or the testes (in men).

3. Function of FSH

In women, FSH:

1. Stimulates the ovaries to recruit a cohort of 10–20 follicles each cycle.
2. Promotes the growth and maturation of these follicles, including the egg they contain.
3. Stimulates the granulosa cells of the dominant follicle to produce oestradiol, which builds the uterine lining.
4. Works with luteinising hormone (LH) to drive the conversion of androgens to oestrogens.

It takes around 85 days for a follicle to develop from its primordial state to the point of ovulation. During this time, FSH supports its growth, and any deficiencies in the woman's energy, blood, lipids, protein or complex carbohydrates can affect the developing egg's quality.

In men, FSH stimulates the Sertoli cells in the testes, which support the production of sperm.

4. Normal FSH levels

The normal level of FSH on day 2 or 3 of the menstrual cycle is approximately 3.5–12.5 IU/mL in most UK and international reference ranges. Mid-cycle FSH peaks briefly during the LH surge, and luteal-phase FSH is low again. Reference ranges vary from country to country and between laboratories; always interpret your own result against the laboratory's reference range.

For practical purposes, an FSH below 10 IU/L on day 2–3 is considered favourable for natural conception and IVF response; above 10–12 IU/L the response to ovarian stimulation is reduced, and above 25–30 IU/L premature ovarian insufficiency should be considered.

5. FSH levels by age

FSH levels typically rise with age, reflecting the decline in ovarian reserve. The following table shows typical day 2–3 FSH ranges by age group:

These are population averages. Individual women vary considerably, and an FSH above the average for one's age does not preclude pregnancy.

6. Causes of high FSH

High FSH typically reflects reduced ovarian function:

1. Diminished ovarian reserve — the most common cause; the ovaries produce less oestradiol so the pituitary increases FSH to compensate.
2. Premature ovarian failure or insufficiency.
3. Menopause and perimenopause.
4. Damage to the ovaries — from surgery, chemotherapy or radiation.
5. Chronic exposure to cold — research has shown that cold exposure can delay follicle growth and impair the ovarian response to FSH.

For full clinical detail on diagnosis, treatment options and natural ways to reduce FSH levels, see my dedicated page: High FSH level — Wokingham, Berkshire.

7. Causes of low FSH

Low FSH typically reflects suppression at the level of the hypothalamus or pituitary:

1. Hypothalamic amenorrhoea — caused by stress, low body fat or excessive exercise.
2. Hyperprolactinaemia — high prolactin suppresses FSH.
3. PCOS — FSH is often relatively low compared with LH, although both may be within reference ranges.
4. Pituitary disease — uncommon, but should be considered if FSH and LH are both low.

8. FSH in men

In men, FSH stimulates spermatogenesis through its action on Sertoli cells. Elevated FSH in a man with a low sperm count generally indicates testicular failure, while a low or normal FSH in a man with a low sperm count points to a problem at the level of the hypothalamus or pituitary.

9. When and how to test FSH

FSH must be measured at a specific point in the cycle to be meaningful. The standard timing in women is day 2 or day 3 of the menstrual cycle (the first day of bleeding counts as day 1). Testing at any other point in the cycle gives a result that cannot be used to assess ovarian reserve. FSH is usually measured alongside oestradiol, because high oestradiol can artificially suppress FSH and mask diminished ovarian reserve.

FSH levels can fluctuate considerably from cycle to cycle, particularly when high. A single result should not be taken as definitive — testing across two or three consecutive cycles gives a more reliable picture.

Reference ranges vary from country to country. Always interpret your test result against the laboratory's own reference range and discuss it with your doctor.

10. FSH in traditional Chinese medicine

In traditional Chinese medicine, high FSH most commonly reflects a deficiency of Kidney Yin and Blood — the foundational substances that nourish the follicles. The pituitary having to "shout louder" to stimulate the ovaries is the western equivalent of TCM's picture of an exhausted reproductive system. Symptoms typically include hot flushes, night sweats, dryness, lower back ache, poor sleep and dark circles under the eyes.

11. Acupuncture and FSH

Research has shown that acupuncture can reduce elevated FSH levels by improving ovarian blood flow and regulating the hypothalamic-pituitary-ovarian axis. Acupuncture also helps to reduce stress and cortisol, which indirectly supports the entire reproductive endocrine system. I have helped many women reduce their FSH from levels above 25–40 IU/L into the normal range, allowing them to conceive naturally or proceed with IVF. See my dedicated page on high FSH level for full clinical detail.

12. Chinese herbal medicine and FSH

Chinese herbal medicine is particularly effective for reducing high FSH. Formulae that nourish Kidney Yin and Blood — such as Zuo Gui Wan, Liu Wei Di Huang Wan and Er Zhi Wan — are most commonly used, often in combination with herbs to gently move the Liver Qi where stress is a factor. Treatment is typically over three to six menstrual cycles, with retesting after this period.

13. Diet, supplements and lifestyle

To support healthy FSH levels and ovarian function:

1. Eat plenty of iron- and protein-rich foods to support Blood and follicle development.
2. Ensure adequate complex carbohydrates (around 250–350 g per day) — sialic acid in complex carbs is important for FSH activity on the follicle.
3. Take a good-quality prenatal supplement.
4. Consider DHEA, coenzyme Q10, royal jelly and bee pollen under professional guidance — these have been shown to improve egg quality.
5. Sleep before 10 p.m. and aim for seven to eight hours per night.
6. Avoid excessive exercise, prolonged dieting and chronic exposure to cold.
7. Reduce psychological stress.

14. Related pages

• Fertility hormones directory
• Luteinising hormone (LH)
• Anti-Müllerian hormone (AMH)
• Oestrogens
• High FSH level (clinical page)
• Low AMH level
• Premature ovarian failure
• My Fertility Guide