Follicle-stimulating hormone (follitropin or FSH for short) is one of the sex hormones. In a woman, it is responsible for the maturation of the egg or follicle growth; in a man, it is responsible for the production of sperm. FSH is produced in the pituitary gland in both sexes.
What is follicle stimulating hormone?
Schematic diagram showing the anatomy and structure of the endocrine (hormone) system. Click to enlarge. Follicle-stimulating hormone is produced in the pituitary gland. Based on its name, it might be assumed that it occurs exclusively in a female; however, this is not the case. FSH is needed for follicle growth, follicle maturation, and indirectly for egg maturation. Men require FSH for sperm formation (spermatogenesis), albeit in a comparably small amount. FSH is thus directly important for fertility in both sexes. FSH deficiency can lead to infertility or inability to conceive.
Production, manufacture, and formation
The female menstrual cycle is controlled by the fine interplay of various hormones. FSH plays a central role in this process. At the beginning of a new cycle, the midbrain first produces gonadotropin releasing hormone (GnRH for short). GnRH stimulates the pituitary gland to produce luteotropin (LH for short) and FSH. FSH causes the maturation of several follicles in the ovaries of the woman. Its activity stimulates estrogen formation in the follicles and at the same time activates the activity of cells inside the follicle – the granulosa cells – which in turn supply the follicle with nutrients. Thus, oocytes mature, which under certain conditions can later be fertilized and grow into an embryo. The production of FSH stops on about the 10th day of the female cycle, namely when the leading follicle has released a mature follicle into the fallopian tube (ovulation). A man’s pituitary gland continuously secretes FSH, albeit in small amounts. In the male body, FSH stimulates the maturation of sperm (spermatogenesis).
Function, action, and properties
FSH is an endogenous hormone produced in the pituitary gland. It is more directly related to a person’s ability to conceive, as it is responsible for both the maturation of eggs capable of fertilization and spermatogenesis in males. The production of FSH is controlled by the hormone GnRH, which is produced in the midbrain. In males, FSH production remains roughly constant throughout his life, i.e. the pituitary gland of the sexually mature male continuously releases a certain amount of FSH. The woman’s body, on the other hand, ceases to be able to conceive around the age of 50 (menopause). At this stage, the midbrain will not produce GnRH and consequently FSH production will also largely cease. Maturation of follicles and ovulation are then no longer possible; a woman can then no longer have a child naturally. Sometimes even relatively young women do not produce FSH or produce the wrong amount. Then neither a leading follicle can develop nor ovulation take place. A woman usually notices this because her menstrual period starts irregularly or not at all, although there is no pregnancy. The lack of FSH is often responsible for polycystic ovary syndrome (PCO). Here, the woman forms countless follicles, but no leading follicle is produced due to the low FSH concentration. Ovulation and pregnancy are then not possible. As part of fertility treatment, FSH deficiency can be regulated by taking medication (e.g., monopreparation Fertavid, Puregon; combination preparation Pergoveris).
Diseases, ailments, and disorders
The most obvious clinical picture of a woman suffering from FSH deficiency is her sterility, and her most common complaint is an irregular menstrual cycle. If FSH underproduction is present, follicles do mature in the body. However, they are not fully formed and no follicle is able to take over the leading function (polycystic ovary syndrome). The result is a disturbed menstrual cycle, since neither ovulation nor the formation and subsequent bleeding of a uterine lining can take place.The woman notices an irregular bleeding up to the complete absence over several months without pregnancy. Since ovulation either occurs irregularly or not at all, the probability of becoming pregnant is low or non-existent. Women with PCO or FSH deficiency can nevertheless have a child as part of fertility treatment. The FSH deficiency can be compensated for with medication (e.g. Puregon), so that the woman either ovulates herself or allows enough fertilizable eggs to mature so that IVF can subsequently be performed. If the woman has an irregular cycle and wishes to have children, a visit to the doctor is always indicated.
