Do you know the 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 is the test or examination of the follicle-stimulating hormone.

Follicle Stimulating Hormone (FSH)

Follicle-stimulating hormone, also called follicle-stimulating hormone or follicle-stimulating hormone (FSH), is a type of gonadotropin hormone. It 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 gland. The pituitary, also called the “pituitary gland,” is a small gland located just below the brain that produces different hormones, which travel into the bloodstream and perform their functions.

Functions in the body

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

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

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

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

Levels

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

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

Menstrual Cycle

Later, when we enter the fertile age, the levels of the follicle-stimulating hormone also vary 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 litre of blood
  • The luteal phase (after ovulation): 2-8 units per liter of blood

Menopause

Finally, at the stage of menopause, the levels of follicle-stimulating hormone increase exaggeratedly , standing between 25 and 135 units per litre of blood.

Abnormal levels of this substance

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

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

1. High levels

Elevated levels of follicle-stimulating hormone may be at the base of specific situations that are worth knowing in both men and women.

1. 1. In women

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

1.2. In men

In men, elevated FSH levels may indicate: castration, alcoholism, receiving chemotherapy, increased testosterone, Klinefelter’s syndrome, taking testosterone-containing drugs, andropause, etc.

2. Low levels

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

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

Follicle-stimulating hormone test

It is very common, especially among women, to perform a follicle-stimulating hormone test. This test measures the amount of follicle-stimulating hormone in a sample of blood.

It is mainly used to evaluate the ovarian function ; this implies the evaluation of the degree of fertility in the woman. Typically, the follicle-stimulating hormone test is carried out in assisted reproduction centres (although not only in these), where women who show difficulties (together with their partner, or not) in becoming pregnant come.

What is the FSH test used for?

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

Specifically, the follicle-stimulating hormone test allows us to determine whether the sex organs, both female and male (ovaries or testicles) are functioning properly, or if there is an underlying problem that makes pregnancy difficult. On the other hand, the test also allows us to confirm if a woman is in the stage of menopause.

Beyond being performed in assisted reproduction centres, this test can also be requested by your gynaecologist or endocrinologist . Thus, other situations that this test allows to be evaluated are

  • Early or delayed puberty
  • Causes of Absent Menstruation
  • Causes of irregular menstruation
  • General functioning of the pituitary gland
  • Presence of a pituitary gland tumor
  • Low sperm count in men
  • Adequate egg production in women

Values

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

Bibliographic references:

  • Carlson, N.R. (2005). Behavioral physiology. Madrid: Pearson Educación.
  • Prieto-Gómez, B. and Velázquez-Paniagua, M. (2002). Physiology of reproduction: gonadotrophin-releasing hormone. Rev Fac Med UNAM, 45(6): 252-257.
  • Rosenweig, M.R., Breedlove, S.M. and Watson, N.V. (2005). Psychobiology: an introduction to behavioural, cognitive and clinical neuroscience. Barcelona: Ariel.