Follicle-stimulating hormone (FSH) is really important for our reproductive health. In this article, find out how to know what normal FSH levels look like, what the symptoms of high and low FSH levels are and how to balance your FSH levels.

Quick facts:

• FSH is a hormone that helps to regulate the menstrual cycle and ovulation.
• FSH stimulates growth of ovarian follicles (eggs) and the production of oestradiol (E2)
• Normal levels of FSH in women change as we age and whether we are pre, peri or postmenopausal
• FSH is regulated by other hormones, including E2 and progesterone.
• High FSH levels can indicate that the ovaries aren’t working properly.
• Low FSH levels can mean your hypothalamus or pituitary gland isn’t working as it should. 
• Find out more about your FSH levels with an at-home Hormone & Fertility Test.

What is FSH? 

FSH stands for Follicle-Stimulating Hormone and is one of the main hormones involved in the regulation of your menstrual cycle and ovulation—making it an important hormone not only for your health but your fertility too.

FSH is what’s known as a gonadotropin hormone. It’s released by the pituitary gland in the brain and then acts on the ovaries.
There is only one other gonadotropin hormone in the body—luteinising hormone (LH). True partners in crime, there’s no FSH without LH, and they act in tandem to bring about changes which essentially regulate ovulation.

Normal FSH levels in women

Because our FSH levels are intricately linked to our ovarian reserve, what’s considered a ‘normal’ FSH level changes as we age. This is because our ovarian reserve declines as we age which makes our FSH levels increase. 

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 from testosterone, 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. Help the follicles grow
2. Help make oestrogen 

Follicular development

FSH does pretty much exactly what it says on the tin—it stimulates the growth of follicles which contain your eggs. 

You’re born with ‘immature’ eggs. So each month, a number of them start maturing before one is released during ovulation. Your eggs are housed in tiny follicles inside your ovaries, and it’s these follicles that FSH signals to prepare your eggs for ovulation (2).

Oestrogen production

FSH also stimulates the cells that surround the follicles to make an enzyme called aromatse, which converts testosterone into oestrogen, another essential hormone for regulating the menstrual cycle and reproductive health (1).

The relationship between FSH and LH

When your eggs are fully mature and ready to be released during ovulation, LH steps in. A surge of LH is released, again by the pituitary gland in the brain, causing the most mature follicle to rupture—releasing an egg into your Fallopian tube. This is ovulation. 

Despite FSH causing numerous follicles, and therefore numerous eggs, to mature each cycle, only one follicle will release an egg each month. This is because FSH and LH are both involved in negative feedback loops, controlled by E2.

But what does negative feedback loop mean?

Increasing FSH levels in the early stages of your menstrual cycle leads to more oestrogen being made, but this ha, a negative feedback effect on FSH levels. In other words, when you have lots of oestrogen, it feeds back to the brain that it needs to stop making more FSH.

Similarly, with LH, oestrogen levels keep increasing through the cycle and once they reach a peak around the middle of the cycle, it causes a sudden surge in LH that promotes ovulation.

After ovulation, the empty follicle that once contained the egg makes another hormone, progesterone, to support conception, implantation and the early stages of pregnancy.

High levels of progesterone tell the brain to stop making more FSH. Now if a pregnancy doesn’t happen, there is a drop in oestrogen and progesterone which triggers your period. It also tells the brain it needs to start making FSH to start the whole process all over again in the next menstrual cycle (5).

High FSH levels

Okay, but what happens when we have high FSH levels? Let’s take a look at the causes and symptoms of high FSH levels.

What causes high FSH levels?

The most common reason for high FSH levels is a low ovarian reserve (egg count), or ovaries that aren’t functioning properly.

When we have a low ovarian reserve, this essentially means we have a smaller number of immature follicles available in our ovaries and our bodies will produce less oestrogen. 

Because oestrogen controls how much FSH we produce (remember that negative feedback loop), when we have less oestrogen, our FSH levels may go up. 

High FSH levels can therefore indicate that our ovaries aren’t functioning properly, be an indicator of low ovarian reserve or an indicator of the onset of menopause.

Other reasons for high FSH levels can be ovarian cancer (although this is very rare) (9) and Premature Ovarian Insufficiency (POI) which is the loss of ovarian function before the age of 40 (6,7).

In some cases, dietary and lifestyle factors can moderately raise FSH levels.

Symptoms of high FSH levels

Symptoms of high FSH levels usually mimic symptoms of menopause and are related to low oestradiol levels —which is why it’s so important to test a range of your reproductive hormones to get to the bottom of symptoms.

Symptoms can include:

• Irregular periods or no periods
• Hot flashes and/or night sweats
• Skin and hair changes
• Difficulty conceiving

How to lower FSH levels?

It is important to understand that if high FSH levels have been caused by menopause or a low egg reserve, modifications to your diet or lifestyle will not be able to reverse this.

However, there are some dietary lifestyle factors associated with a higher FSH, such as smoking and high alcohol consumption. 

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.

Nutrition can be a really powerful tool in balancing hormones and helping to alleviate symptoms. You can book a nutritional health consultation with one of our registered nutritionists via your health hub.

Low FSH levels

What do low FSH levels mean? 

Commonly, low FSH levels can be caused by the pituitary gland in the brain not functioning properly. This is also known as hypopituitarism.

Problems with the pituitary gland can be directly related to the gland itself, or with the hypothalamus—another part of the brain that controls the release of FSH. This can result in a disorder known as hypogonadotropic hypogonadism.

This can be caused by high levels of stress or an energy deficiency i.e. burning more calories than we are taking in through our diet. It can therefore be common in people who are very underweight, such as those who suffer from eating disorders, or who exercise without adequate fuel. This can eventually result in your periods stopping, which is a condition known as hypothalamic amenorrhea.

Other less common causes of low FSH levels include glucocorticoids or meningitis.

Symptoms of low FSH levels

Symptoms of low FSH can include:

• Low sex drive
• Fatigue
• Infertility
• Hot flashes
• Irregular periods or no periods

Low FSH levels can mean that our ovaries are not maturing enough eggs. But again, symptoms can mimic symptoms from lots of other conditions, so testing a range of different reproductive hormones is important to get a clearer idea of what’s going on.

How to increase FSH levels?

Diet and lifestyle changes can only improve FSH levels—but only if the root cause of low FSH levels are linked to diet or lifestyle factors.

If you think you could be in an energy deficiency, balancing your energy intake could improve your FSH levels, in addition to reducing any excessive exercise.

You can read more about the relationship between exercise and fertility and how much exercise is too much here

Find out more about your FSH levels

Diet and lifestyle changes can only improve FSH levels—but only if the root cause of low FSH levels is linked to diet or lifestyle factors.

If you think you could be in an energy deficiency, balancing your energy intake could improve your FSH levels, in addition to reducing any exercise.

Resources

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