Follicle stimulating hormone: what is it and how it affects our body

Do you know about follicle stimulating hormone (FSH)? It is a hormone linked to fertility. The levels of it vary in situations such as: fertility problems, pregnancy situation or under hormonal treatment, among others.

In this article we will see all about this hormone: what are its functions, where it occurs, what are the “normal” levels during the different stages of the menstrual cycle, which implies abnormal levels (both low and high) of the same and, finally, what the follicle stimulating hormone test or examination consists 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 gland; the pituitary gland, also called the “pituitary gland”, is a small gland located just below the brain, which produces various hormones, which travel to the bloodstream and perform their functions.

    Functions in the body

    What role does this hormone play in men and women? In humans, the follicle-stimulating hormone is involved in the synthesis of sperm. In women, its function is linked to the regulation of the maturation of the organism up to the stage of puberty. Moreover, in this sense, it is the hormone responsible for stimulating estrogen synthesis.

    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 at an earlier stage than mature eggs (which eventually become mature eggs).

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

    So this is a hormone closely related to fertility in both men and women. Their levels, as we will see later, allow us to determine if the sexual organs are functioning well, or if there are problems (facing abnormal levels).


      Levels of follicle stimulating hormones vary throughout life. To get a general idea, before puberty, their levels vary from 0 to 0.4 units of FSH per liter of blood.

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

      menstrual cycle

      Later, when we entered the fertile age, levels of follicle stimulating hormones also vary during the menstrual cycle. Within the menstrual cycle we find three main phases or periods:

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


      finally during menopause, levels of follicle stimulating hormones increase excessively, By placing them between 25 and 135 units per liter of blood.

      Abnormal levels of this substance

      What happens when our levels of follicle stimulating hormones become abnormal? Various pathological situations can trigger this fact, such as: suffering from anorexia, underweight, lack of ovulation, suffering from a pituitary or hypothalamic disorder, etc.

      On another side, in pregnancy Levels of follicle stimulating hormones may also change suddenly or be abnormal.

      1. High levels

      High levels of follicle stimulating hormone can cause specific situations that should be known to both men and women.

      1. 1. In women

      In the case of women, high FSH levels may indicate: menopausal or postmenopausal situation (already mentioned), premature menopause, on hormonal treatment, if you suffer from polycystic ovary syndrome, if you have Turner syndrome (A genetic disease that affects the development of girls, where the X chromosome is not there or is incomplete), if you have some type of tumor in the pituitary gland, etc.

        1.2. at men’s

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

        2. Low levels

        On the other hand, low hormone levels in women indicate ovarian dysfunction during egg production, pregnancy, anorexia nervosa, Being treated with birth control pills or corticosteroids, etc.

        In contrast, in men, low hormone levels indicate the existence of one of these conditions: decreased function of the pituitary gland (or hypothalamus), being under stress, low weight or produce few sperm.

        The follicle-stimulating hormonal test

        It is very common, especially in women, to perform a follicle stimulating hormone test. This test measures how much of this hormone we have from a blood sample.

        It is mainly used to assess ovarian function; it is a question of evaluating the degree of fertility of the woman. As a rule, the follicle stimulating hormone test is carried out in assisted reproduction centers (but not only in these), where women who have difficulty (with their partner or not) will become pregnant.

        What is the FSH test used for?

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

        Specifically, the follicle stimulating hormone test can determine whether the sexual organs, both female and male (ovaries or testes) are functioning properly, or if there are underlying issues that make pregnancy difficult. On the other hand, the test also confirms whether the woman is at the stage of menopause.

        In addition to being performed in assisted reproduction centers, this test may also be requested by your gynecologist or endocrinologist.. Thus, other situations allowing to evaluate this test are:

        • Precocious or delayed puberty
        • Causes of missing menstruation
        • Causes of irregular periods
        • General functioning of the pituitary gland
        • Presence of a tumor in the pituitary gland
        • Below the sperm count in men
        • Egg production suitable for women


        When the follicle stimulating hormone test is performed, reference values ​​of the population are consulted, by age and sex of the person in question. It also takes into account which phase of the menstrual cycle you are in.

        Bibliographical references:

        • Carlson, NR (2005). Behavioral physiology. 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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