FSH, or follicle-stimulating hormone, is a hormone that plays a key role in regulating the reproductive system. It helps to stimulate the production of sperm in the testicles, and is essential for the development of a high sperm count and sperm quality.
A normal FSH indicates that the function and maturation of the so-called Sertoli cells in the testicles, essential for sperm production, are optimal.
FSH is mainly measured in men when investigating and evaluating infertility. As a consequence, it can also be measured to monitor effectiveness of treatments. Measuring FSH can provide important information on testicle function and pituitary gland function.
Sometimes, FSH is also measured as part of a more extensive testing, when investigating suspected hypogonadism (testosterone deficiency) or Klinefelter syndrome (a genetic disorder where men are born with an extra X-chromosome). In both of these conditions, FSH may be increased as a direct result of lower testosterone production.
High levels of FSH indicate that the testicles and sperm production aren’t fully functioning as they should. This is because high levels suggest that the hypothalamus and the pituitary gland, regulating the function of the testicles, are trying to compensate for a problem with the reproductive system.
In general, when the testicles are not functioning properly, FSH may increase as an attempt to stimulate sperm production. For this reason, high levels of FSH can be a sign of reduced sperm production and even infertility.
Important note: FSH levels can fluctuate during the day, and high FSH levels alone will not be enough for diagnosis, and must be analyzed and evaluated in a context together with other tests and symptoms.
Low FSH levels indicate that there is an issue with FSH production. This can for instance be the result of a dysfunctioning pituitary gland or hypothalamus, regions in the brain regulating the production of hormones, including FSH.
Another decreasing factor on FSH is excessive alcohol consumption. Although the effect is not as consistent as on lowering levels of LH, FSH levels can be suppressed by high intakes of alcohol. FSH levels may also decrease due to chronic stress, severe malnutrition and as a normal effect of aging.