FSH Test
Note: this site is for informational purposes only. To view test results or book a test, use the NHS app in England or contact your GP.
This test measures the level of follicle-stimulating hormone (FSH) in a blood sample to assess how well the pituitary gland and reproductive organs are functioning. It is used to investigate fertility problems, menstrual irregularities, delayed or early puberty, and menopause, and to evaluate disorders affecting the ovaries or testes.
Why get tested?
To evaluate the function of your pituitary gland, which regulates the hormones that control your reproductive system.
When to get tested?
If you are having difficulty getting pregnant or are having irregular menstrual periods (in order to identify or rule out ovarian failure/menopause in women and sperm production failure in men); if your doctor thinks that you have symptoms of a pituitary, ovarian, testicular or hypothalamic disorder; when your doctor suspects that a child has delayed or earlier than expected sexual maturation (or delayed or early growth).
Sample required?
A blood sample taken from a vein in your arm.
Test preparation needed?
No special preparation is required for the test, but the blood sample should be taken at the start of a woman’s cycle (days 1 to 4 if the cycles are regular).
What is being tested?
Follicle-stimulating hormone (FSH) is made by the pituitary gland in the brain. The production and release of FSH and LH in the pituitary gland is stimulated by gonadotrophin releasing hormone (GnRH) present in the hypothalamus. Control of FSH and LH production is a complex feedback system being regulated by oestradiol from the ovaries or testosterone from the testes.
In women, FSH stimulates the growth and development of ovarian follicles (unfertilised eggs) during the follicular phase of the menstrual cycle. This cycle is divided into two phases, the follicular and the luteal, by a mid-cycle surge of FSH and luteinising hormone (LH). Ovulation (release of the egg from the ovary) occurs shortly after this mid-cycle surge of hormones. During the follicular phase, FSH initiates the production of oestradiol by the follicle, and the two hormones work together in the further development of the egg follicle. During the luteal phase, FSH stimulates the production of progesterone. Both oestradiol and progesterone help the pituitary control the amount of FSH produced. At the time of the menopause, the ovaries stop functioning and FSH levels rise. During pregnancy, oestrogen levels are high and this makes FSH undetectable.
In men, FSH stimulates the testes to produce mature sperm. 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). At about 6–8 years, levels again rise with the beginning of puberty and the development of secondary sexual characteristics.
How is the sample collected for testing?
A blood sample is taken by needle from a vein, normally in the arm.
Is any test preparation needed to ensure the quality of the sample?
No, but in a woman, the sample should be taken in the first 4 days of her cycle if the periods are regular (day 1 is the first day of full bleeding). If the test is for the menopause, for example, and periods are stopping then the FSH can be taken at any time but occasionally repeat samples may be needed. This is because it can take a couple of years for the ovaries to stop working completely and results may be contradictory when the menopause first starts to occur. It is important to note that the test should not be performed if a woman is taking female hormones (for example contraceptives such as the combined oestrogen and progestogen or high-dose progestogen pill) as this will affect the interpretation of results.
Common questions
FSH is often used in conjunction with other tests (LH, testosterone, oestradiol, and progesterone) in the investigation of infertility in both men and women. FSH levels are also useful in the investigation of menstrual irregularities (irregular periods) and to aid in the diagnosis of pituitary gland disorders. In children, FSH and LH are used to diagnose delayed or precocious (early) puberty and investigate problems with growth.
- In women and men, FSH and LH are requested as part of the investigation of infertility and pituitary gland disorders.
- FSH may also be used to see if a woman has reached the menopause, however this is only recommended in women aged 40 to 45 years with menopausal symptoms, including a change in their menstrual cycle (please see NICE guidelines Menopause | Guidance and guidelines | NICE (NG23)).
- FSH can also be helpful in diagnosing an early menopause also known as premature ovarian insufficiency in women under 40 years of age. FSH is useful when there are early symptoms of the menopause including no or erratic periods. In this case NICE (23) guidelines state that premature ovarian insufficiency is based on raised FSH levels on 2 blood samples taken 4 – 6 weeks apart.
- FSH levels also help to find the reason a man has a low sperm count.
- In children, FSH and LH may be used when a boy or girl does not appear to be entering puberty at an appropriate age (either too late or too soon) or when they are shorter or taller than expected.
In women, FSH and LH levels can help to tell the difference between primary ovarian failure (failure of the ovaries themselves) and secondary ovarian failure (failure of the ovaries due to disorders of either the pituitary gland or the hypothalamus in the brain). Increased levels of FSH and LH are consistent with primary ovarian failure. Some causes of primary ovarian failure are listed below.
Developmental defects:
- Ovarian agenesis (failure to develop ovaries)
- Chromosomal abnormality, such as Turner’s syndrome
- Ovarian steroidogenesis defect, such as 17 alpha hydroxylase deficiency
Premature ovarian failure due to:
- Radiation therapy
- Chemotherapy
- Autoimmune disease
Chronic anovulation (failure to ovulate) due to:
- Polycystic ovary syndrome (PCOS)
- Adrenal disease
- Thyroid disease
- Ovarian tumour
When a woman enters the menopause and her ovaries stop working, FSH levels will rise. This is a normal process with the average age in the UK of onset estimated at 51 years old, however the normal age range is very wide but it is rare to be affected younger than 40 years old (approximately 1% of women).
Low levels of FSH and LH with low levels of oestrogen are consistent with secondary ovarian failure due to a pituitary or hypothalamic problem.
In men, high FSH levels are due to primary testicular failure and indicate very little or no sperm production. This can happen if the testes do not grow properly or are injured.
Developmental defects:
- Gonadal agenesis (failure to develop testes)
- Chromosomal abnormality, such as Klinefelters syndrome
Testicular failure:
- Viral infection (mumps)
- Trauma
- Radiation therapy
- Chemotherapy
- Autoimmune disease
- Germ cell tumour
Low levels of FSH are consistent with pituitary or hypothalamic disorders and can be seen in the eating disorder anorexia nervosa and starvation.
In young children, high levels of FSH and LH and development of secondary sexual characteristics at an unusually young age are an indication of precocious (early) puberty. This is much more common in girls than in boys.
In delayed puberty, LH and FSH levels can be normal or below what is expected for a youth within this age range. A test for LH response to GnRH (sometimes called LHRH) may need to be performed along with other testing to diagnose the reason for the delayed puberty.
FSH results can be increased with use of certain drugs, such as cimetidine, clomiphene, digitalis, and levodopa. FSH results can decrease with oral contraceptives (the pill), phenothiazines, and hormone treatments.
The basic test for infertility is measurement of progesterone to check that ovulation is occurring. Other tests for infertility include FSH and LH and oestrogen to assess your reproductive hormone levels. A post-sexual intercourse test may be done where the cervical mucous is examined 2–8 hours after intercourse to check if the sperm are surviving in it. A hysterosalpingogram (image of fallopian tubes) may be done to see whether your fallopian tubes are blocked. Your partner may be asked to give a specimen of semen for analysis.
You may have polycystic ovary syndrome (PCOS), a hormonal problem seen in 7–10% of women and a major cause of infertility. With this condition, ovaries may become larger because of cysts that form in them. Women with PCOS also may have high levels of testosterone often together with a high ratio of LH to FSH and do not ovulate normally. A combination of medications and hormone therapy may help your symptoms.
Men also produce FSH and LH in their bodies, and these hormone levels are important for male reproduction too. In men, FSH stimulates the testes to produce sperm just as in women FSH stimulates the ovaries to produce eggs. In men, LH can be measured to investigate the cause of a low testosterone.