Follicle-stimulating Hormone (FSH)
For women, when you are having difficulty getting pregnant or are having irregular or no 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 puberty
A blood sample is drawn by needle from a vein.
No test preparation is needed, but a woman's sample should be collected at specific times during 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.
FSH is made by the pituitary gland, a small organ located in the center of the head behind the sinus cavity 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 of childbearing age, 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. Less is known about FSH levels in aging men.
- 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 puberty.
How is the test used?
- 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 when or if a woman is entering 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 normal patterns of development and true disease. Once it is established that symptoms are a result of true disease, further testing can be done to identify the underlying cause.
When is it ordered?
For a woman, an FSH test may be ordered when she is having difficulty getting pregnant, has irregular or an absence of menstrual periods, or sometimes when it is suspected that she 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 healthcare 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 healthcare practitioner will consider all the information from the workup to establish a diagnosis.
FSH and LH levels can help to differentiate between a condition affecting the ovaries themselves (primary) and dysfunction of the ovaries due to disorders of either the pituitary or the hypothalamus (secondary).
High levels of FSH and LH are consistent with conditions affecting the ovaries themselves. Some examples include:
- Failure to develop ovaries (ovarian agenesis)
- Chromosome disorder, such as Turner syndrome
- Defect in the steroid production by the ovaries, such as 17 alpha hydroxylase deficiency
Damage to the ovaries due to:
Underlying conditions that affect ovary function, such as:
When a woman enters menopause and her ovaries stop working, FSH levels will rise.
Low levels of FSH and LH are consistent with a pituitary disorder or problem with the hypothalamus.
Low FSH serum levels have been associated with increased risk of ovarian cancer.
High FSH levels are due to conditions affecting the testicles themselves. Some examples include:
- Viral infection (mumps)
- Trauma, injury
- Radiation exposure
- Autoimmune disease
- Germ cell tumor
- Failure to develop normal gonads (gonadal agenesis)
- Chromosome disorder, such as Klinefelter syndrome
Low levels are consistent with pituitary or hypothalamic disorders. See the article on Pituitary Disorders for more information.
Higher levels of FSH and LH than expected for age plus the development of secondary sexual characteristics at an unusually young age are an indication of early 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)
Normal prepubescent levels of LH and FSH in children exhibiting some signs of puberty may indicate a condition called "peripheral precocious puberty." The signs and symptoms are brought on by elevated levels of the hormones estrogen or testosterone. This may be caused by:
- Tumors that produce and release hormones
- Adrenal gland tumors
- Ovarian tumors or cysts
- Testicular tumors
Normal FSH and LH levels with a few signs of puberty (e.g., development of pubic hair and acne) may signal a previous environmental exposure to agents, such as testosterone cream or gel, or may 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. Examples of some causes of delayed puberty include:
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 man need a test for FSH and LH? I thought these were female hormones.
Is there a home test for FSH?
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 falsely elevated in people who are taking large doses of biotin as this can interfere with immunoassays. FSH results can be decreased with oral contraceptives, phenothiazines, and hormone treatments. FSH will also be low when women are pregnant.