Index
It is one of the gonadotrophic hormones, and the other is the luteinizing hormone. Both are released by the pituitary gland into the bloodstream.
Function
Follicle stimulating hormone is one of the essential hormones for pubertal development and the function of the ovaries in women and the testes in men.
In women, this hormone stimulates the growth of ovarian follicles in the ovary prior to the release of an egg from a follicle at ovulation. It also increases the production of estradiol.
In men, follicle-stimulating hormone acts on the Sertoli cells of the testes to stimulate sperm production (spermatogenesis).
Alternative names for follicle-stimulating hormone
Other names for this hormone are:
- FSH.
- Follitropin (pharmaceutical preparations).
How is follicle stimulating hormone controlled?
The production and release of follicle stimulating hormone is regulated by the levels of various circulating hormones released by the ovaries and testes.
This system is called the hypothalamic-pituitary-gonadal axis. Gonadotropin-releasing hormone is released from the hypothalamus and binds to receptors in the anterior pituitary gland to stimulate both the synthesis and release of follicle-stimulating hormone and luteinizing hormone.
The released follicle-stimulating hormone is transported into the bloodstream where it binds to receptors in the testes and ovaries. Using this mechanism, follicle stimulating hormone, along with luteinizing hormone, can control the functions of the testes and ovaries.
In women, when hormone levels drop towards the end of the menstrual cycle, this is detected by nerve cells in the hypothalamus.
These cells produce more gonadotropin-releasing hormone, which in turn stimulates the pituitary gland to produce more follicle-stimulating hormone and luteinizing hormone, and releases them into the bloodstream.
Increased follicle stimulating hormone stimulates follicle growth in the ovary. With this growth, the follicle cells produce increasing amounts of estradiol and inhibin.
In turn, the production of these hormones is detected by the hypothalamus and pituitary gland and less gonadotropin-releasing hormone and follicle-stimulating hormone will be released.
However, as the follicle grows, and more estrogen is produced from the follicles, it simulates an increase in luteinizing hormone and follicle-stimulating hormone, which stimulates the release of an egg from a mature follicle (ovulation).
Therefore, during each menstrual cycle, there is an increase in the secretion of follicle stimulating hormone in the first half of the cycle that stimulates follicular growth in the ovary.
After ovulation, the ruptured follicle forms a corpus luteum that produces high levels of progesterone. This inhibits the release of follicle stimulating hormone.
Towards the end of the cycle, the corpus luteum breaks down, progesterone production decreases, and the next menstrual cycle begins when follicle-stimulating hormone begins to rise again.
In men, follicle-stimulating hormone production is regulated by circulating levels of testosterone and inhibin, both produced by the testes.
Follicle-stimulating hormone regulates testosterone levels and, when they increase, they are detected by the nerve cells of the hypothalamus, thus decreasing the secretion of gonadotropin-releasing hormone and, consequently, follicle-stimulating hormone.
The opposite occurs when testosterone levels drop. This is known as “negative feedback” control to keep testosterone production stable.
Inhibin production is also controlled in a similar way, but this is detected by cells in the anterior pituitary gland rather than the hypothalamus.
What if I have too much follicle stimulating hormone?
Very often, elevated levels of follicle-stimulating hormone are a sign of malfunction in the ovary or testicle.
If the gonads do not create enough estrogen, testosterone, and / or inhibin, proper feedback control of the pituitary gland’s follicle-stimulating hormone production is lost and levels of follicle-stimulating hormone and luteinizing hormone will increase.
This condition is called hypergonadotropism and hypogonadism, and it is associated with primary ovarian failure or testicular failure. This is seen in conditions such as Klinefelter syndrome in men and Turner syndrome in women.
In women, follicle-stimulating hormone levels also begin to increase naturally in women in the menopausal period, reflecting a reduction in the function of the ovaries and decreased production of estrogen and progesterone.
There are very rare pituitary conditions that can raise follicle-stimulating hormone levels in the bloodstream.
This overwhelms the normal negative feedback loop and can (rarely) cause ovarian hyperstimulation syndrome in women.
Symptoms of this include enlarged ovaries and a potentially dangerous accumulation of fluid in the abdomen (triggered by increased ovarian steroid production), resulting in pain in the pelvic area.
What if I have too little follicle stimulating hormone?
In women, a lack of follicle-stimulating hormone leads to incomplete development at puberty and poor ovarian function (ovarian failure). In this situation, the ovarian follicles do not grow properly and do not release an egg, which leads to infertility.
Since the levels of follicle stimulating hormone in the bloodstream are low, this condition is called hypogonadotropism – hypogonadism. This is seen in a condition called Kallman syndrome, which is associated with a reduced sense of smell.
Sufficient action of follicle stimulating hormone is also needed for proper sperm production. In the case of the complete absence of follicle stimulating hormone in men, lack of puberty and infertility due to lack of sperm (azoospermia) can occur.
Partial follicle-stimulating hormone deficiency in men can cause delayed puberty and limited sperm production (oligozoospermia), but it may be possible to father a child. If the loss of follicle-stimulating hormone occurs after puberty, there will be a similar loss of fertility.
