Follicle-Stimulating Hormone (FSH): Function and Normal Values in Women

Published: 23 February 2024|Last updated: 23 February 2024|About Assisted Reproduction.|

FSH (Follicle-Stimulating Hormone) is a key player in the intricate machinery of women’s fertility. It is a hormone that is produced in the brain, specifically in the pituitary gland. Once released into the bloodstream, its challenging task is to regulate a crucial part of the female menstrual cycle.

What is the exact function of Follicle-Stimulating Hormone (FSH)?

The primary role of FSH is to stimulate the growth and subsequent development of ovarian follicles.

What are ovarian follicles?

Ovarian follicles are microscopic structures located within the ovary. When a girl is born, her ovaries already contain small groups of cells known as primordial follicles, each containing an immature oocyte surrounded by a thin layer of cells.

Throughout a woman’s reproductive life, some of these primordial follicles mature into primary follicles. In each menstrual cycle, one of them becomes the dominant follicle that will be selected to release the oocyte into the fallopian tube during ovulation.

What does FSH do?

FSH plays a crucial role in selecting the dominant follicle and promoting the growth of follicles in the ovary. Additionally, it stimulates the production of oestrogen by these follicles.

During the menstrual cycle, there is a peak release of FSH into the blood, triggering ovulation. Subsequently, FSH levels decrease, and these hormonal changes are essential for the maturation and release of the oocyte.

What if FSH levels are low?

As seen, FSH levels vary throughout the menstrual cycle. In the follicular phase, they should be high, while in the luteal phase, they should decrease. Typical FSH values range from 4.7 to 21.5 mIU/mL, but these values may vary depending on age and stage of the menstrual cycle.

Abnormally low FSH levels in a fertile woman can lead to the failure of follicle stimulation, resulting in no oocyte being released and insufficient oestrogen function, potentially causing difficulties in conceiving.

What causes FSH alterations in women?

A very low value of FSH hormone in women indicates no ovulation.

Low FSH levels can be attributed to various reasons, with the most common being:

  • Very low body weight or recent rapid weight loss: inadequate body weight or sudden weight loss can lead to low FSH levels.
  • Kallmann syndrome: this genetic disorder affects the entire reproductive system, including FSH production.
  • Pituitary tumours: the presence of a tumour in the pituitary gland can disrupt FSH production.
  • Chronic stress: despite seeming unlikely, prolonged stress significantly influences women’s hormonal regulation and can cause disruptions in FSH production.

Conditions associated with high FSH levels include:

  • Undeveloped ovaries: ovaries that did not develop normally.
  • Primary ovarian insufficiency: insufficient functioning of the ovaries.
  • Polycystic ovary syndrome (PCOS): a condition characterized by the presence of multiple cysts on the ovaries.
  • Menopause or perimenopause: the natural cessation of menstruation or the transitional period leading to menopause.
  • Ovarian tumour: the presence of a tumour in the ovaries.
  • Thyroid diseases or adrenal gland disorders: conditions affecting the thyroid or adrenal glands can lead to elevated FSH levels.
  • Chromosomal disorders, such as Turner syndrome: genetic conditions affecting the X chromosome that can result in abnormal FSH levels.

Treatment for low FSH levels

Detecting low FSH levels is crucial to addressing fertility issues. Understanding the cause is essential for tailoring the correct treatment, such as:

  • Hormone therapy: recommended to stimulate ovarian function in cases of primary ovarian insufficiency (POI). Ovarian stimulation is often recommended for women trying to conceive.
  • Stress management: using techniques like meditation, cognitive-behavioural therapy, and exercise.
  • Other treatments: for instance, specific treatments to address tumours.

In any case, at Eugin, we can help identify the underlying causes of fertility problems associated with low FSH levels and guide you to the appropriate treatment.

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