Definition
The abbreviation FSH stands for follicle stimulating hormone. This hormone belongs to the sex hormones and is responsible for the maturation of the germ cells in women and men. The FSH level in women decreases and increases during the course of the female cycle. Furthermore, it is also important in puberty for the development of the reproductive organs. FSH is released by the pituitary gland, a small hormonal gland in the brain, also called the pituitary gland.
Function
As a sex hormone, FSH, in combination with other hormones, leads to the maturation of germ cells in both men and women. In women, FSH acts on cells surrounding the egg, producing estrogen and promoting the maturation of the egg. The egg cell with these cells is called a follicle.
However, in order for only one follicle to mature each month in a woman, and for the lining of the uterus to prepare for a possible pregnancy, it is important that FSH and the other sex hormones are precisely coordinated. The concentrations of the different hormones vary during a cycle and influence each other. FSH promotes oestrogen synthesis, but at the same time the release of FSH is inhibited by high oestrogen levels.
The FSH level initially rises immediately after menstruation and ensures that a follicle matures. Shortly before ovulation, approximately after 14 days, the FSH initially drops and then rises sharply for a short time at the time of ovulation. In men the FSH concentration is more constant. Here, the target site of FSH is certain cells in the testes (Sertoli cells or nurse cells), which under the influence of FSH control sperm maturation with the help of testosterone. Also at the beginning of puberty, the FSH level, along with other sex hormones, increases, which leads to the development of the reproductive organs.
What does the value say?
FSH levels change over the course of life and the monthly cycle. After menstruation and after ovulation the values are between 2-10 U/l. Near ovulation the values are higher.
Here, values up to 30 U/l are still normal. -After menopause, the FSH level rises even more strongly. Values above 20 U/l are the norm.
They can also rise above 100 U/l. In contrast, very low values below 1.5 U/l are found during pregnancy. In men, the FSH values are between 2-10 U/l.
In women and men, FSH is released intermittently and irregularly, so that a certain margin in the values has no disease value. In children, the standard values differ in the different age groups. During the menopause, elevated values are normal.
This is because FSH release is inhibited by high estrogen levels. However, estrogen production decreases steadily during the menopause, as the function of the ovaries slowly ceases and estrogen can no longer be produced. This results in menstrual cycles without ovulation and high FSH levels.
FSH levels are also elevated in other causes of ovarian hypofunction, such as after removal of an ovary. This is because even in these cases there is no feedback and inhibition of FSH release by estrogen. Elevated FSH levels shortly before ovulation are completely normal.
Here, a high concentration of FSH is necessary for the development of the egg cell and thus for fertility. In men, increased FSH levels can also occur. This is also caused by an underfunction of the gonads, which can be hereditary, for example.
Stress is a harmless cause of reduced FSH levels. Anorexia also causes menstrual bleeding to stop because, among other things, the FSH levels are too low. This also makes sense because in this situation the body does not have enough resources to maintain a pregnancy.
A rarer cause can also be polycystic ovarian syndrome, which is a metabolic disease with many cysts in the ovaries. Another cause in both women and men may be hypofunction of the anterior pituitary gland (anterior pituitary insufficiency). Here, not enough FSH is produced and the FSH concentration in the body drops.
Reasons for anterior pituitary lobe insufficiency can be tumors, trauma, bleeding or inflammation. Autoimmune processes, i.e. processes in which the body turns against itself, are also possible causes. However, disturbances in the hypothalamus can also lead to lowered FSH concentrations, since the gonatropin-releasing hormone is produced there, which stimulates FSH release.
