FSH hormone levels

FSH hormone levels

Follicle-stimulating hormone (FSH) is produced by the pituitary gland situated at the base of the brain. It is released from this gland into the bloodstream and plays an essential role with regards to the ovaries. Its purpose is to stimulate follicle growth and selection and it also plays a role in maturing the egg which will later be released during ovulation.

In cases of ovarian insufficiency, the pituitary gland attempts to compensate for this by increasing FSH secretion. This happens in a physiological manner during the menopause and, as a result, women going through this stage have FSH levels which are far above those in women of childbearing age.

If abnormally high levels of FSH (>10 lU/L) are detected at a young age, this can be a suggestion of low ovarian reserve which reduces the possibility of getting pregnant naturally.

But detecting FSH with a view to evaluating ovarian reserve has a number of limitations:

  • FSH levels vary across the menstrual cycle and they can vary from one laboratory to another depending on the detection technique used. The reference values used in our laboratory are indicated in the following table:
Follicular phase (prior to ovulation) 3,03-8,08   UI/l
Midcycle 2,55-16,69 UI/l
Luteal phase (following ovulation) 1,38-5,47   UI/l
Menopause >26,72       UI/l
  • Because of this variation, in order to evaluate ovarian reserve, the analysis needs to be carried out between the second and fourth day of the menstrual cycle.
  • The FSH value obtained over several cycles can vary. Therefore, an isolated result in a given cycle could lead to an incorrect poor reserve diagnosis.

As a result of the limitations of determining FSH in evaluating ovarian reserve, currently most clinics specialised in reproduction use anti-Müllerian hormone along with an antral follicle count (an ultrasound which needs to be carried out under basal conditions or, in other words, between the second and fourth day of the menstrual cycle) in order to give experts an understanding of a woman’s ovarian reserve. As such, medical decisions can be taken based on the results obtained.

Dr Ana Fabregat, pharmacist at Instituto Bernabeu

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