Follicle stimulating hormone (FSH) is a hormone made by the pituitary gland in the brain. Both men and women produce FSH but it has slightly different functions in each gender. It is a hormone which is essential for our development during puberty and is associated with the function of the ovaries in females and the testes in men.
The production of FSH is a multifaceted approach involving other hormones such as gonadotrophin-releasing hormone (GnRH). Because these hormones are made by the ovaries, testes, pituitary gland or hypothalamus, producing FSH is complex.
In females, FSH levels along with luteinising hormone (LH) levels can distinguish between primary and secondary ovarian failure. If levels of FSH and LH are increased then this is indicative of primary ovarian failure. Whereas low FSH and LH alongside low oestrogen levels show secondary ovarian failure.
Increased FSH levels will rise when a woman enters the menopause because her ovaries will no longer work. In men, high levels of FSH are a result of testicular failure and confirm there is little or no sperm production.
It is important your FSH levels are measured at the correct time during your cycle. FSH levels fluctuate during your cycle and your sample should be taken within the first four days to give the most accurate result. If you are going through the menopause, on the other hand, your sample can be taken at any time.
You can test your FSH levels along with other key fertility hormones by purchasing a simple at-home finger prick test kit which is then analysed at an accredited lab. Forth offers a number of blood tests which include FSH such as Female Fertility, Male Hormones, Perimenopause & Menopause Health
FSH has regulatory functions in the reproductive systems of both males and females.
In females, FSH is an important hormone in the menstrual cycle because it promotes the growth and development of ovarian follicles during the follicular phase of the cycle. Ovarian follicles are fluid-filled sacs which contain immature eggs, during ovulation a mature egg is released from an ovarian follicle. As the follicles mature, a dominant follicle eventually takes over and releases oestradiol and inhibin, suppressing the secretion of FSH.
The levels of FSH peak at the same time as a surge in luteinising hormone which causes ovulation. During the next stage of the menstrual cycle, known as the luteal phase, FSH levels are reduced to prevent the development of new follicles. However, during this phase, FSH is responsible for stimulating the production of another hormone, progesterone. Oestrogen and progesterone help the pituitary gland control the amount of FSH is produced.
In men, FSH production is controlled by circulating levels of testosterone and inhibin, both of which are produced by the testes. Testosterone is regulated by FSH. Therefore, when testosterone levels increase nerve cells in the hypothalamus detect the rise so GnRH and FSH production can be reduced. When testosterone levels fall, the opposite happens, this is known as a negative feedback loop. As a result, testosterone production is maintained at a steady rate. Inhibin is controlled in a similar way but changes are detected by the pituitary gland rather than the hypothalamus. Increased FSH levels are associated with a reduction in sperm production, usually occurring with low inhibin levels. This is due to a disturbed feedback loop between the hypothalamus, pituitary gland and testes.
Because high levels of FSH are associated with a defect in the ovaries or testes, the effects can interfere with your everyday life, particularly as it may hinder your chances of having a baby. Increased levels of FSH are associated with primary ovarian failure or testicular failure. Infertility is responsible for many psychological and social issues for both couples and individuals. As a result, failure to conceive has been associated with reduced sexual intimacy, depression and stress. 
In women, FSH levels rise naturally around the time of the menopause, highlighting the reduced function of the ovaries as well as the reduction in oestrogen and progesterone production. The menopause can negatively affect wellbeing because of both the psychological and physical symptoms during the transition.
If you are worried about your FSH level or just want to check where you fall on the range, you can test your level with a simple at-home blood test.
Changes in FSH levels may be caused by an imbalance in the pituitary gland or the hypothalamus. Equally, individuals who have had eating disorders like anorexia and bulimia tend to have reduced FSH levels.
A common reason for increased levels of FSH in females is the menopause. FSH is released to cause ovulation by maturing ovarian follicles. However, during the menopause, the ovaries stop working and no longer produce follicles. Usually, once a follicle matures and releases an egg, a structure called the corpus luteum forms which produces progesterone and suppresses the release of FSH. However, because there are no follicles and subsequently no corpus luteum, FSH levels continue to rise.
The menopause causes differing levels of hormones in the system, which are responsible for various side effects, including:
Primary ovarian failure can present with similar symptoms to the menopause. It is most commonly associated with:
Making improvements to your lifestyle can help to reduce the symptoms associated with increased FSH levels or may help with your fertility. A key factor in reproductive issues is obesity. Therefore, it is important to stay within a healthy weight range.
When menstruating, it is essential women keep their iron levels adequate to deal with the blood loss. Foods which are good sources of iron include:
You should aim to eat a healthy, balanced diet which incorporates essential fatty acids to help increase hormone levels.
Exercise is also important. Controlled weight loss in overweight individuals has been shown to help restore reproductive function. Exercise is also great for psychological issues too, like depression and mood changes which have been linked to the menopause.
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