Follicle-stimulating Hormone (FSH)
For women, when you are having difficulty getting pregnant or are having irregular or absence of menstrual periods
For men, when your partner cannot get pregnant, or you have a low sperm count, low muscle mass or decreased sex drive
When a healthcare practitioner suspects that a child has delayed or earlier than expected sexual maturation
None, but the timing of a woman's sample will be correlated with her menstrual cycle.
Follicle-stimulating hormone (FSH) is a hormone associated with reproduction and the development of eggs in women and sperm in men. This test measures FSH in the blood or urine.
FSH is made by the pituitary gland, a grape-sized organ located at the base of the brain. Control of FSH production is a complex system involving the hypothalamus in the brain, the pituitary gland, and the hormones produced by the ovaries or testicles. The hypothalamus releases gonadotropin-releasing hormone (GnRH), which stimulates the pituitary to release FSH and luteinizing hormone (LH), a closely related hormone also involved in reproduction.
- In women, FSH stimulates the growth and maturation of eggs (follicles) in the ovaries during the follicular phase of the menstrual cycle. The menstrual cycle is divided into the follicular and the luteal phases, with each phase lasting about 14 days. During this follicular phase, FSH initiates the production of estradiol by the follicle, and the two hormones work together in the further development of the egg follicle. Near the end of the follicular phase, there is a surge of FSH and luteinizing hormone. Release of the egg from the ovary (ovulation) occurs shortly after this surge of hormones. The hormone inhibin as well as estradiol and progesterone help control the amount of FSH released by the pituitary gland. FSH also facilitates the ability of the ovary to respond to LH.
As a woman ages and menopause approaches, ovarian function wanes and eventually ceases. As this occurs, FSH and LH levels rise.
- In men, FSH stimulates the testicles to produce mature sperm and also promotes the production of androgen binding proteins. FSH levels are relatively constant in men after puberty.
- In infants and children, FSH levels rise shortly after birth and then fall to very low levels by 6 months in boys and 1-2 years in girls. Concentrations begin to rise again before the beginning of puberty and the development of secondary sexual characteristics.
Disorders affecting the hypothalamus, pituitary, and/or the ovaries or testicles can cause the production of too much or too little FSH, resulting in a variety of conditions such as infertility, abnormal menstrual cycles, or early (precocious) or delayed sexual maturation (puberty).
How is the sample collected for testing?
A blood sample is drawn by needle from a vein in the arm. Sometimes, a random urine sample is collected but, due to the cyclic secretion of FSH, a 24-hour collection of urine may be requested. By measuring FSH levels produced over a 24-hour period, the variation in FSH levels seen throughout the day can be minimized.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed, but a woman's sample should be collected at specific times during her menstrual cycle.
How is it used?
The test for follicle-stimulating hormone (FSH), a hormone associated with reproduction and the development of eggs in women and sperm in men, has several uses.
- Determine the cause of infertility
- Diagnose conditions associated with dysfunction of the ovaries or testicles
- Aid in the diagnosis of pituitary or hypothalamus disorders, which can affect FSH production
In women, FSH levels are also useful in:
- The investigation of menstrual irregularities
- Predicting onset or confirmation of menopause
In men, FSH levels are used to help determine the reason for a low sperm count.
In children, FSH and LH are used to help diagnose delayed or precocious (early) puberty. Irregular timing of puberty may be an indication of a more serious problem involving the hypothalamus, the pituitary gland, the ovaries or testicles, or other systems. The measurement of LH and FSH may differentiate between benign symptoms and true disease. Once it is established that symptoms are a result of true disease, further testing can be done to discern the underlying cause.
When is it ordered?
For a woman, an FSH test may be ordered when she is having difficulty getting pregnant or has irregular or an absence of menstrual periods.
FSH may be ordered when a woman's menstrual cycle has stopped or become irregular, to determine if the woman has entered menopause.
For a man, the test may be ordered when his partner cannot get pregnant, when he has a low sperm count, or when he has low muscle mass or decreased sex drive, for example.
In both women and men, testing may be ordered when a health practitioner suspects that a pituitary disorder is present. A pituitary disorder can affect the production of several different hormones, so there may be signs and symptoms in addition to some of those listed above. They can include fatigue, weakness, unexplained weight loss, and decreased appetite to name a few.
In children, FSH and LH may be ordered when a boy or girl does not appear to be entering puberty at an appropriate age (either too late or too soon). Signs of puberty may include:
- Breast enlargement in girls
- Growth of pubic hair
- Growth of the testicles and penis in boys
- Beginning of menstruation in girls
What does the test result mean?
As part of an infertility workup, a high or low FSH is not diagnostic but provides a piece of information on what may be the cause. For example, a hormone imbalance may affect a woman's menstrual cycle and/or ovulation. A health practitioner will consider all the information from the workup to establish a diagnosis. See the Infertility article for more on this.
FSH and LH levels can help to differentiate between primary ovarian failure (failure of the ovaries themselves) and secondary ovarian failure (failure of the ovaries due to disorders of either the pituitary or the hypothalamus).
High levels of FSH and LH are consistent with primary ovarian failure. Some causes of primary ovarian failure are listed below.
- Failure to develop ovaries (ovarian agenesis)
- Chromosomal abnormality, such as Turner syndrome
- Defect in the steroid production by the ovaries, such as 17 alpha hydroxylase deficiency
Premature failure of the ovaries due to:
- Radiation exposure
- Autoimmune disease
Chronic failure to ovulate (anovulation) due to:
When a woman enters menopause and her ovaries stop working, FSH levels will rise.
Low levels of FSH and LH are consistent with secondary ovarian failure due to a pituitary disorder or hypothalamic problem. Low FSH serum levels have been associated with increased risk of ovarian cancer.
High FSH levels are due to primary testicular failure. This can be the result of developmental defects in testicular growth or to testicular injury, as indicated below.
- Failure to develop gonads (gonadal agenesis)
- Chromosomal abnormality, such as Klinefelter syndrome
Low levels are consistent with pituitary or hypothalamic disorders. See the article on Pituitary Disorders for more information.
High levels of FSH and LH with the development of secondary sexual characteristics at an unusually young age are an indication of precocious puberty. This is much more common in girls than in boys. This premature development is usually due to a problem with the central nervous system and can have a few different underlying causes. Examples include:
- Central nervous system tumor
- Brain injury, trauma
- Inflammation within the central nervous system (e.g. meningitis, encephalitis)
- Brain surgery
Normal prepubescent levels of LH and FSH in children exhibiting some signs of pubertal changes may indicate a condition call "precocious pseudopuberty." The signs and symptoms are brought on by elevated levels of the hormones estrogen or testosterone. This may be caused by:
- Hormone-secreting tumors
- Adrenal gland tumors
- Ovarian tumors or cysts
- Testicular tumors
Normal FSH and LH levels with a few signs of puberty can also be a benign form of precocious puberty with no underlying or discernable cause or may just be a normal variation of puberty.
In delayed puberty, LH and FSH levels can be normal or below what is expected for a youth within this age range. Some of the causes for delayed puberty can include:
- Dysfunction of the ovaries or testicles
- Hormone deficiency
- Turner syndrome
- Klinefelter syndrome
- Chronic infections
- Eating disorder (anorexia nervosa)
Is there anything else I should know?
FSH results can be increased with use of certain drugs, including cimetidine, clomiphene, digitalis, and levodopa. FSH results can be decreased with oral contraceptives, phenothiazines, and hormone treatments. FSH will also be low when women are pregnant. A recent nuclear medicine scan may interfere with results of the FSH test if it is measured by a radioimmunoassay, which is seldom used any more.
I’m having a hard time getting pregnant. What tests do I need?
Basic tests for infertility often include measuring FSH and luteinizing hormone (LH) levels. Your healthcare provider may also ask you to keep track of your body temperature, which rises slightly during ovulation. Other hormonal tests as well as a postcoital (after intercourse) examination may be done. A hysterosalpingogram (image of fallopian tubes) may be ordered to see whether your fallopian tubes are blocked. Your partner may be asked to give a specimen of semen for analysis.
Why would a woman have multiple FSH tests done and a man only have one?
Why would a man need a test for FSH and LH; I thought these were female hormones?
Is there a home test for FSH?
On This Site
Elsewhere On The Web
Hormone Health Network: The Endocrine System, Endocrine Glands & Types of Hormones
Hormone Health Network: Infertility and Women
KidsHealth.org: Precocious puberty
The Magic Foundation: Precocious puberty
MedlinePlus Medical Encyclopedia: Klinefelter syndrome
MedlinePlus Medical Encyclopedia: Turner syndrome