Follicle-Stimulating Hormone: What Do Your FSH Levels Mean?

October 6, 2021Bríd Ní Dhonnabháin BSc (hons), MSc

If FSH and LH sound familiar, that’s because we talk about them a lot, especially when it comes to fertility and ovulation. Here, we’re putting the spotlight on FSH, so that you can understand it in detail. You can read more about its partner in crime, LH, here. Let’s start with a whistle-stop tour of everything you need to know about follicle-stimulating hormone and what your FSH levels mean. Read on for more detail.

  1. What is FSH? Follicle-stimulating hormone, or FSH, is a hormone released by the pituitary gland in the brain that acts on the ovaries. 
  1. What does it do?  FSH plays an important role in the production of oestradiol (E2) and the growth of ovarian follicles – AKA your eggs. 
  1. How is FSH regulated?  FSH is regulated by other hormones, including E2 and progesterone, acting on the hypothalamus to either increase or decrease FSH production. 
  1. What does high FSH mean and what causes it? High FSH levels can indicate primary ovarian insufficiency (POI), the menopausal transition, or Turner syndrome. FSH levels can also be higher in heavy smokers or drinkers or people with a vitamin D deficiency. 
  1. What does low FSH mean and what causes it?  Low FSH levels can mean your hypothalamus or your pituitary gland aren’t working as they should. It can also indicate energy deficiency in a person, meaning more calories are being burned than eaten. This is often seen with eating disorders or in people who exercise a lot. 
  1. What can I do to manage my FSH?  Some changes to diet and lifestyle can help with hormone imbalances. Quitting smoking and drinking can help lower FSH levels and decreasing soy intake may help increase it. For more information, talk to one of our Hertility experts. 

What is FSH? 

Gonadotropic hormones are hormones released from the pituitary gland in the brain and released into the bloodstream. Gonadotropins then go on to act on the ovaries. There are two types of gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The pituitary gland produces FSH which acts on the ovaries to stimulate the growth of follicles containing your eggs. As well as growing the ovarian follicles, FSH stimulates the granulosa cells that surround the follicle to produce oestrogen, an essential hormone for regulating the menstrual cycle (1). You can read more about oestrogen here. 

What does FSH do?

FSH has two primary functions: 

  1. Oestrogen production 
  2. Follicular development 

Oestrogen production

Oestrogen is essential for regulating the menstrual cycle and for reproductive health. When FSH reaches the ovaries, it acts on granulosa cells to produce an enzyme called aromatase, which then converts androgens (testosterone) which were released from nearby cells, into oestradiol (E2), a form of oestrogen (2). 

Follicular development

The eggs in your ovaries start off as immature. Each month, a number of them start a maturation process in response to hormones, and the most mature egg is released from the ovary into the fallopian tube in a process called ovulation. One of the hormones involved in the maturation process is FSH (2). 

Increasing FSH levels in the early stages of your menstrual cycle leads to more E2, which has a negative feedback effect on FSH levels. In other words, when you have lots of E2 it feeds back to the region of the brain that released the FSH and tells it to stop. That way, when it’s time to ovulate, only the follicle with the greatest amount of oestrogen stores can withstand the declining FSH and this is the egg that is eventually released during ovulation. The remaining follicles disintegrate. At this point, the E2 and remaining FSH act on the cells surrounding the follicle to make it more responsive to  LH. A surge in the hormone LH, therefore, causes the follicle to rupture, releasing the egg into the fallopian tube in the process of ovulation (3,4). 

How is FSH regulated? 

After ovulation, the empty follicle that once contained the egg produces the hormone progesterone to support conception, implantation and the early stages of pregnancy. The high levels of progesterone prevent the release of more FSH from the pituitary gland. The empty follicle breaks down if no embryo implants into the lining of the uterus. This causes a drop in progesterone which allows for FSH production to start again at the beginning of the next menstrual cycle (5). 

Your menstrual cycle starts again with your next period, which is triggered by the drop in your estradiol and progesterone levels. The drop in these hormones is sensed by the hypothalamus in the brain which begins to produce gonadotropin-releasing hormone (GnRH), which travels to the pituitary to produce FSH and LH. These are then released into the bloodstream and FSH then acts on the ovaries to grow the follicles containing your eggs(1). Is this starting to sound familiar? 

What do high FSH levels mean?

A high FSH level can mean a number of things. When the number of immature follicles remaining in the ovary is small, we produce more FSH in order to successfully mature an egg each month for ovulation. Ovaries that have a low number of eggs or aren’t functioning properly produce very little E2, and therefore the negative feedback which tells the brain to produce less FSH is no longer there. As a high FSH level is therefore a signal that your ovaries aren’t working properly, it is often used to check if someone is going through menopause i.e. the end of your ability to ovulate.  In women under 40, a high FSH level can mean primary ovarian insufficiency (POI), which is the loss of ovarian function before the age of 40 (6,7). 

High FSH levels are also seen in people with Turner syndrome, a genetic disorder that affects sexual development (8). For some people, high FSH levels can also indicate ovarian cancer, though this is very rare (9). 

Sometimes, FSH levels can be elevated due to dietary and lifestyle factors and therefore modifications in these areas may reduce them.  However, it is important to understand that if high FSH levels have been caused by menopause, modifications to your diet or lifestyle will not be able to reverse this.  Dietary and lifestyle factors that can cause or contribute to elevated FSH levels include: 

  • Smoking (10,11,12) 
  • Excessive alcohol use (13) 
  • Vitamin D deficiency (14,15) 
  • Polychlorinated biphenyls (PCBs) (16,17)

What do low FSH levels mean? 

Low FSH levels can mean your ovaries are not maturing enough eggs or that your pituitary gland (which releases FSH) is not working correctly. Problems with the pituitary gland can be directly related to the gland itself, or with the hypothalamus, further, back the chain of hormone command. Low FSH levels can also be the result of an energy deficiency. This is when a person is burning more calories than they’re taking in from their diet and is seen in people who are very underweight or who exercise excessively. 

Other causes of low FSH levels include: 

  • A diet rich in soy products or isoflavones (18,19)
  • Glucocorticoids (10) 
  • Eating disorders (21,22)
  • Excessive exercise (23,24)
  • A meningitis infection in the previous 12 months (25,26)

What can I do to manage my FSH levels?

If your FSH levels are elevated and you are a regular smoker or drinker, consider taking steps to reduce these habits. If you’re trying to conceive, consider cutting alcohol and cigarettes completely as this will improve your chances of conception and prevent harmful effects to the baby during pregnancy (17). For advice on how to quit smoking, see the full list of NHS quit smoking services here.

Vitamin D deficiency has many negative effects on health, including disrupting hormone balances. Our bodies create vitamin D when our skin is exposed to the sun. However, due to long, sunless winters and improved skincare regimens that include daily SPF wearing, vitamin D deficiencies are becoming more common. If you’re vitamin D deficient, you may want to include a vitamin D supplement in your diet and this may help with hormonal imbalances. However, you must always consult a doctor before taking supplements.

If your FSH levels are on the lower side, it may be worth re-evaluating your diet and exercise regime. Excessive exercise is known to disrupt the release of GnRH from the hypothalamus which has knock-on effects on FSH and LH levels. You can read more about the relationship between exercise and fertility and how much exercise is too much here. If you regularly consume soy or isoflavone products, these may cause excessively high levels of oestrogens, which as we mentioned, suppresses FSH release from the pituitary. However, data on the effects of soy on oestrogen is conflicting and further studies are needed. If you have a vegan diet and regularly use soy-based meat and dairy substitutes, you may want to consider switching to other plant-based protein sources. 

If you have a prescription for glucocorticoid medication or you have had meningitis in the previous 12 months, these can temporarily decrease your FSH levels due to disrupting the release of GnRH from the hypothalamus. 

If you’re concerned about your FSH results and would like to speak to someone, we recommend booking a consultation with one of our Hertility experts. 

Trusted Resources

  1. Follicle stimulating hormone 
  2. Physiology, Follicle Stimulating Hormone – StatPearls – NCBI Bookshelf 
  3. The Normal Menstrual Cycle and the Control of Ovulation 
  4. Luteinizing hormone and follicle stimulating hormone synergy: A review of role in controlled ovarian hyper-stimulation 
  5. Stimulatory and inhibitory effects of progesterone on FSH secretion by the anterior pituitary 
  6. Primary ovarian insufficiency: an update 
  7. Idiopathic primary ovarian insufficiency: a study of serial hormonal profiles to assess ovarian follicular activity
  8. FSH may be a useful tool to allow early diagnosis of Turner syndrome
  9. FSH and LH serum/tumor fluid ratios and malignant tumors of the ovary.
  10. Follicle-stimulating hormone concentrations in relation to active and passive smoking
  11. Smoking, alcohol and caffeine in relation to ovarian age during the reproductive years
  12. Ovarian function and cigarette smoking in the BioCycle Study 
  13. Alcohol intake induces diminished ovarian reserve in childbearing age women – Li – 2013 – Journal of Obstetrics and Gynaecology Research – Wiley Online Library 
  14. Association between serum 25-hydroxyvitamin D and ovarian reserve in pre-menopausal women 
  15. Is the ovarian reserve influenced by vitamin D deficiency and the dress code in an infertile Iranian population? 
  16. Persistent organic pollutants as predictors of increased FSH:LH ratio in naturally cycling, reproductive age women 
  17. Preconception care: caffeine, smoking, alcohol, drugs and other environmental chemical/radiation exposure 
  18. Effects of soy protein and isoflavones on circulating hormone concentrations in pre- and post-menopausal women: a systematic review and meta-analysis 
  19. Effects of soy foods on ovarian function in premenopausal women 
  20. Glucocorticoids, Stress, and Fertility 
  21. Eating disorders from a gynecologic and endocrinologic view: hormonal changes 
  22. Obstetric and gynecologic problems associated with eating disorders 
  23. A review of the pathophysiology of functional hypothalamic amenorrhoea in women subject to psychological stress, disordered eating, excessive exercise or a combination of these factors 
  24. Effect of Exercise on Ovulation: A Systematic Review 
  25. Prospective investigation of pituitary functions in patients with acute infectious meningitis 
  26. Hypothalamic pituitary dysfunction in acute nonmycobacterial infections of central nervous system 

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