Follicle-stimulating Hormone: What Is It And How Does It Affect Our Body

What is follicle stimulating hormone? How does it affect the functioning of the body?

Follicle Stimulating Hormone

Are you familiar with follicle-stimulating hormone (FSH)? It is a hormone linked to fertility. Its levels vary in situations such as: fertility problems, pregnancy situation or being under hormonal treatment, among others.

In this article we will see everything about this hormone: what are its functions, where is it produced, what are the “normal” levels of it during the different stages of the menstrual cycle, what implies abnormal levels (both low and high) of it and Finally, what does the follicle stimulating hormone test or exam consist of?

Follicle Stimulating Hormone (FSH)

Follicle-stimulating hormone, also called follicle-stimulating hormone or follicle-stimulating hormone (FSH), is a type of gonadotropin hormone. This hormone is found in humans and also in other mammals.

Its function is essential in the reproductive cycle, and it participates in both sexes in growth and development.

Follicle-stimulating hormone is produced in the pituitary; The pituitary gland, also called the “pituitary gland,” is a small gland located just below the brain that produces different hormones, which travel to the bloodstream and perform their functions.

Functions in the body

What role does this hormone have in men and women? In the case of men, follicle stimulating hormone is involved in the synthesis of sperm. In women, its function is related to the regulation of the maturation of the organism until the stage of puberty. In addition, in this sense, it is the hormone in charge of stimulating the synthesis of estrogens.

On the other hand, in the first phase of a woman’s menstrual cycle, follicle-stimulating hormone modulates oocyte maturation. Oocytes are female germ cells; that is, they are cells in a stage prior to that of mature ovules (which end up becoming these).

In addition, follicle-stimulating hormone is a marker that allows diagnosing certain gynecological irregularities in women, in relation to infertility and menstruation (rule).

Thus, it is a hormone closely linked to fertility, both in men and women. Their levels, as we will see later, allow us to determine if the sexual organs are working well, or if there is a problem (with abnormal levels).


The levels of follicle stimulating hormone vary throughout life. To get a general idea, before puberty, your levels range from 0 to 0.4 FSH units per liter of blood.

As we grow and once we enter the stage of puberty, its levels increase to 0.3 and 10 units per liter of blood.

Menstrual cycle

Later, when we enter the fertile age, the levels of follicle stimulating hormone also change during the menstrual cycle. Within the menstrual cycle, we find three major phases or periods:

  • The follicular phase (which occurs before ovulation): 2-10 units per liter of blood.
  • The ovulatory phase (during ovulation): 8-20 units per liter of blood.
  • The luteal phase (after ovulation): 2-8 units per liter of blood.


Finally, in the menopausal stage, the levels of the follicle-stimulating hormone increase exaggeratedly, reaching between 25 and 135 units per liter of blood.

Abnormal levels of this substance

What happens when our levels of follicle stimulating hormone become abnormal? Various pathological situations can trigger this, such as: suffering from anorexia, being underweight, having no ovulation, suffering from a disorder of the pituitary or hypothalamus, etc.

On the other hand, in a pregnancy situation the levels of follicle stimulating hormone can also change abruptly or be abnormal.

1. Elevated levels

Elevated levels of follicle-stimulating hormone can be the basis of specific situations that should be known, both in men and women.

1. 1. In women

In the case of women, elevated levels of FSH may indicate: menopausal or postmenopausal situation (already mentioned), premature menopause, when undergoing hormonal treatment, if you suffer from polycystic ovary syndrome, if you have Turner Syndrome (a genetic disorder that affects the development of girls, where the X chromosome is missing, or is incomplete), if you have any type of tumor in the pituitary, etc.

1.2. In men

In men, elevated FSH levels could indicate: castration, alcoholism, receiving chemotherapy, increased testosterone, suffering from Klinefelter Syndrome, taking medications containing testosterone, andropause, etc.

2. Low levels

On the other hand, low levels of the hormone in women indicate a malfunction of the ovaries when producing eggs, pregnancy, anorexia nervosa, being on contraceptive pills or corticosteroids, etc.

On the other hand, in men, low levels of the hormone indicate the existence of one of these situations: reduced function of the pituitary (or hypothalamus), being under stress, underweight or producing few sperm.

The follicle stimulating hormone test

It is very common, especially among women, to perform a follicle-stimulating hormone test. What this test does is measure the amount we have of this hormone through a blood sample.

It is used mainly to evaluate ovarian function ; This implies the evaluation of the degree of fertility in the woman. Typically, the follicle-stimulating hormone test is performed in assisted reproduction centers (although not only in these), where women who show difficulties (with their partner, or not) attend to become pregnant.

What is the FSH test used for?

We have seen the usefulness of the FSH test in determining potential fertility problems in both women and men.

Specifically, the follicle-stimulating hormone test makes it possible to determine if the sexual organs, both female and male (ovaries or testicles) are working properly, or if there is an underlying problem that makes pregnancy difficult. On the other hand, the test also allows to confirm if the woman is in the menopausal stage.

Beyond being performed in assisted reproduction centers, this test can also be requested by your gynecologist or endocrinologist. Thus, other situations that allow to evaluate this test are:

  • Precocious or delayed puberty
  • Causes of the absence of menstruation
  • Causes of irregular menstruation
  • General function of the pituitary gland
  • Presence of a tumor in the pituitary gland
  • Low sperm count in men
  • Production of adequate ovules in women


When the follicle-stimulating hormone test is performed, the reference values ​​of the population are consulted, according to the age and gender of the person in question. The phase of the menstrual cycle you are in is also taken into account.

Bibliographic references:

  • Carlson, NR (2005). Physiology of behavior. Madrid: Pearson Education.
  • Prieto-Gómez, B. and Velázquez-Paniagua, M. (2002). Reproductive physiology: gonadotropin-releasing hormone. Rev Fac Med UNAM, 45 (6): 252-257.
  • Rosenweig, MR, Breedlove, SM and Watson, NV (2005). Psychobiology: An Introduction to Behavioral, Cognitive, and Clinical Neuroscience. Barcelona: Ariel.

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