FSH: normal values, functions and their importance in fertility

Follicle stimulating hormone, or FSH, is a hormone produced by a gland in the brain called the pituitary gland.

This hormone is important for both men and women because it helps regulate the reproductive system.

We talked to the medical director of Vida Fertility Alicante, Dr. Alejandra García-Villalba about how FSH works, what values are normal, and what medications to take in cases of problems getting pregnant.

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In women

FSH stimulates the ovaries to develop follicles, which are small structures where eggs are found. It also regulates the menstrual cycle, a monthly process that prepares a woman’s body for a possible pregnancy.

In addition, FSH is used in some medications to help women who are having trouble getting pregnant. These drugs help stimulate the ovaries so that follicles are stimulated and all activated follicles develop.

What functions and how does FSH influence a woman’s fertility?

FSH is a hormone that plays a crucial role in a woman’s menstrual cycle. It is important that its levels remain stable to avoid irregularities in the cycle.

At the beginning of the menstrual cycle:

FSH is released from the brain and acts on the ovaries.
This causes the primordial follicles, which contain eggs, to start growing.

During follicle development:

The growing follicles begin to produce another hormone called oestradiol.
Oestradiol acts on the brain and reduces the production of FSH.

Selection of the dominant follicle:

The decrease in FSH causes only one of the growing follicles to survive, known as the dominant follicle or Graaf’s follicle.
The other follicles are arrested and lost.

Ovulatory and luteal phase:

The FSH level rises again during the ovulatory phase of the menstrual cycle, but remains low during the luteal phase until menstruation arrives and a new cycle begins.

FSH: Normal hormone values

FSH tests should be done at the beginning of the menstrual cycle. It is recommended to test on day 3 of the cycle, three days after the onset of menstruation.

Normal FSH values should be between 3-9 mIU/ml. An FSH level outside this range may indicate a problem or disturbance in the menstrual cycle.

An interpretation of FSH levels can be made on day 3 of the cycle, although we must bear in mind that it can be affected by multiple causes and one value does not lead to a diagnosis:

Less than 6 mIU/ml → Probable Optimal ovarian reserve.
Between 6 and 9 mIU/ml → Probable Good ovarian reserve.
From 9 to 10 mIU/ml → Probable Moderate level of ovarian reserve.
Between 10 and 13 mIU/ml → Probable Low ovarian reserve.
Above 13 mIU/ml → Probable very low ovarian reserve, usually associated with perimenopause or onset of menopause.

*These values may vary slightly between different laboratories or due to different medical conditions.

Let us look at these alterations:

Low FSH

Underweight: Having a very low body weight can affect FSH production.
Anorexia: This eating disorder can lead to low FSH levels due to lack of nutrients.
Very rapid weight loss: Losing weight rapidly can upset hormone balance, including FSH.
Hypogonadism: A condition in which the sex glands produce little or no sex hormone.
Pregnancy: During pregnancy, FSH levels naturally decrease.

High FSH

Low ovarian reserve: Indicates that the ovaries have fewer eggs available.
Menopause: During menopause, FSH levels increase because the ovaries stop functioning.
Contraceptives: Some contraceptives can affect FSH levels.
Turner syndrome: This is a genetic condition that affects female development and can lead to high FSH levels.
Pituitary tumours: Tumours in the pituitary gland can alter FSH production.

FSH testing should be done in conjunction with testing for other reproductive hormones to get a more accurate diagnosis.

How is it measured?

When do you order an FSH test?

You may need an FSH test if your healthcare professional thinks you may have a problem with your pituitary gland. These problems can affect fertility. They can also cause symptoms such as

Decreased appetite and/or weight loss.

In women:

High FSH levels are normal in the perimenopause and menopause. The body produces more hormones to promote follicular growth so that ovulation can occur.

However, you may need an FSH test along with other hormone tests if you have a medical reason, such as:

If you have not been able to get pregnant after 1 year of trying to get pregnant.
If you have irregular or missed periods.
Premature menopause (age 40 or younger).
Early menopause (before age 45).
Menopause-related symptoms whose cause is unclear.
Decreased sexual interest.

In men:

If after a year of trying to get pregnant it is not possible.
If sexual appetite decreases
Indication by seminogram: azoospermia/oligozoospermia.
Loss of muscle mass or body hair

In men

At puberty, the male develops FSH levels that activate the function of the testes and, together with testosterone, in the production of sperm.

FSH helps to produce sperm (spermatogenesis), which are the cells necessary for reproduction.

Functions in male fertility

FSH plays a key role by acting on the Sertoli cells, located in the seminiferous tubules of the testis. These cells are responsible for providing protection and nourishment to the spermatogonia, which are the precursors of spermatozoa, making them essential to the process of spermatogenesis.

Both FSH and testosterone are essential in stimulating and maintaining sperm production in the testis. In addition, this process has an autoregulatory mechanism similar to that occurring in the ovary, in which the hormone inhibin plays a crucial role. Inhibin is released by the testis and signals the pituitary to reduce FSH production, thus preventing overstimulation of spermatogenesis.

Normal FSH hormone values in men

Assessment of male fertility is mainly based on the seminogram, but FSH analysis in men can also provide valuable information when alterations in seminal parameters are detected.

FSH values in men usually range between 1 and 12 mIU/ml. However, if these values are outside this range, there may be testicular dysfunction associated with different causes:

Low FSH: may be related to hypogonadotropic hypogonadism, hyperprolactinaemia induced by the use of antidepressants or antihypertensives, among other factors.
High FSH: may be associated with a history of chemotherapy or radiotherapy, pituitary tumours, Klinefelter’s syndrome or the natural ageing process (andropause).

* It is important to note that reference values for hormone tests may vary slightly depending on the laboratory where they are performed.

In case of abnormal FSH values, it is advisable to consult a fertility specialist for a more precise diagnosis and to determine the most appropriate treatment.

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What drugs should I take to regulate?

If you are trying to get pregnant and your FSH levels are altered, FSH-based drugs are essential in assisted reproduction treatments, such as artificial insemination (AI) or in vitro fertilisation (IVF).

Their main function is to stimulate follicular development in the ovarian stimulation phase, allowing several follicles to mature at the same time rather than selecting a single dominant follicle.

How does work in fertility treatment?

The continuous administration of this hormone makes it easier to obtain several mature eggs in IVF treatments, thus increasing the possibility of generating viable embryos after fertilisation in the laboratory.

Learn about the IVF process in Spain

Who should take FSH during assisted reproduction treatment?

Medications containing FSH can be prescribed to women during the IVF process. Men can also be prescribed if required depending on the case.

This hormone is key to stimulating follicular development in women and sperm production in men where it is deemed necessary.

In women:

Patients with polycystic ovary syndrome (PCOS) who have alterations in ovulation.
Women with low ovarian reserve, in whom the aim is to improve ovarian response in fertility treatments.
Patients suffering from anovulation.
Cases in which there have been previous failures in stimulation cycles with clomiphene citrate.

In men:

Patients with hypogonadotropic hypogonadism, either congenital or acquired origin.
Men with azoospermia of hormonal origin, in whom FSH administration may favour sperm production.

How to choose the right fertility treatment?

Choosing the right fertility treatment is not just a medical decision. Factors such as ovarian response and the individual needs of each patient must be considered.

If you want to know what is the best option for you, at Vida Fertility we can help you design a personalised plan, contact us and take the first step towards motherhood!

Ask us about your case

Frequently asked questions about FSH hormone

High FSH at the age of 40

Dr. Alejandra García-Villalba answers:

High FSH is usually a sign that the ovarian reserve (the number of eggs in the ovaries) is decreasing. This can happen naturally with age or due to premature ovarian failure.

To better understand a woman’s fertility and whether IVF treatment can work, it is important to test not only FSH, but also anti-Müllerian hormone (AMH) and to perform ultrasound scans.

If FSH is very high and ovarian reserve is low, IVF with a woman’s own eggs may be less successful, especially in women over 40.
If donor eggs are used, the chances of success increase significantly, as the donor eggs come from young women with good fertility.

If you have doubts about your chances of pregnancy with a high FSH, it is best to talk to a specialist to assess all available options.

Normal FSH values in menopause

Dr. Alejandra García-Villalba responds:

Normal FSH values in menopause range from 25.8 to 134.8 mIU/mL.

*These values may vary slightly between different laboratories.

What is the level to get pregnant?

Dr. Alejandra García-Villalba answers:

FSH hormone is a key indicator to evaluate a woman’s ovarian reserve. Generally, when its values are between 3 and 9 mIU/ml, ovarian reserve is considered to be adequate.

An interpretation of FSH levels can be made on day 3 of the cycle, although we must bear in mind that it can be affected by multiple causes and one value does not lead to a diagnosis:

Less than 6 mIUI/ml → likely Optimal ovarian reserve.
Between 6 and 9 mIU/ml → likely Good ovarian reserve.
9 to 10 mIU/ml → likely Moderate level of ovarian reserve.
Between 10 and 13 mIU/ml → likely Low ovarian reserve.
Above 13 mIU/ml → likely very low ovarian reserve, which is often associated with perimenopause or the onset of menopause.

* It is important to note that reference values for hormone tests may vary slightly depending on the laboratory where they are performed. This is due to differences in the measurement methods and equipment used for the analyses.

Therefore, it is always advisable to interpret the results with the help of a fertility specialist, who will be able to evaluate the values according to your particular case and determine the best course of action.

Causes of an elevated FSH

Dr. Alejandra García-Villalba responds:

FSH is a hormone that regulates fertility in both men and women.

In women: FSH can be high if the ovaries have less ovarian reserve, which happens when the woman has low ovarian reserve or has reached menopause. It can also be high if there are genetic problems such as Turner’s syndrome or if there are tumours in a part of the brain called the pituitary gland.

In men: High FSH may be because the testicles are not producing enough sperm. This can happen after chemotherapy or radiotherapy, if there are genetic problems such as Klinefelter’s syndrome, or with age, as FSH levels tend to rise in older men.

If you think something is wrong with your hormone levels, it is best to talk to a specialist doctor to analyse the cause and find a solution.

Ask us about your case