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Diagnostic Tests 2023

FSH: what é, what it is for and why it is á high or low

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FSH: what é, what it is for and why it is á high or low
FSH: what é, what it is for and why it is á high or low

FSH, known as follicle-stimulating hormone, is produced by the pituitary gland and has the function of regulating sperm production and egg maturation during childbearing age. Thus, FSH is a hormone linked to fertility and its concentration in the blood helps to identify whether the testes and ovaries are working properly.

The reference values of the FSH test vary according to the age and gender of the person and, in the case of women, with the phase of the menstrual cycle, and may also be useful to confirm menopause.


What the FSH exam is for

This exam is usually ordered to assess whether the couple has their fertility preserved, if they are having difficulties getting pregnant, but it can also be ordered by the gynecologist or endocrinologist to assess:

  • Causes of missed menstruation or irregular menstruation;
  • Early or delayed puberty;
  • Sexual impotence in men;
  • If the woman has already entered menopause;
  • If the testes or ovaries are working properly;
  • Low sperm count in men;
  • If the woman is producing eggs properly;
  • The function of the pituitary gland and the presence of a tumor, for example.

Some situations that can change the result of the FSH test are the use of contraceptive pills, tests with radioactive contrast, such as those performed for the thyroid, as well as the use of drugs such as Cimetidine, Clomiphene and Levodopa, for example. The doctor may recommend that the woman stop taking the contraceptive pill 4 weeks before having this test.

FSH reference values

FSH values vary by age and gender. In infants and children, FSH is either not detectable or is detectable in small concentrations, and its production begins normally at puberty.

The reference values of FSH can vary according to the laboratory, and therefore the values that each laboratory uses as a reference must be observed. However, here is an example:

Children: up to 2.5 mIU/ml

Adult male: 1, 4 - 13.8 mIU/mL

Adult woman:

  • In the follicular phase: 3, 4 - 21.6 mIU/mL
  • In the ovulatory phase: 5.0 - 20.8 mIU/ml
  • In the luteal phase: 1.1 - 14.0 mIU/ml
  • Menopause: 23.0 - 150.5 mIU/ml

Normally FSH is not requested during pregnancy, as the values change a lot during this period due to hormonal changes. Learn how to identify the phases of the menstrual cycle.

Possible FSH changes

According to the test result, the doctor will indicate what is causing the increase or decrease in this hormone, taking into account age, and whether it is male or female, but the most common causes of this type of change are:

FSH High

  • In Women: Loss of ovarian function before age 40, post-menopause, Klinefelter syndrome, use of medications with progesterone, estrogen.
  • In Men: Loss of testicle function, castration, increased testosterone, Klinefelter syndrome, use of testosterone medications, chemotherapy, alcoholism.


  • In a woman: The ovaries are not producing eggs properly, pregnancy, anorexia nervosa, use of corticosteroids or the contraceptive pill.
  • In men: Low sperm production, decreased pituitary or hypothalamus function, stress or low weight.

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