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 and in women aged under 40 years in whom menopause is suspected (please see NICE guidelines Menopause | Guidance and guidelines | NICE). 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.
Ovarian agenesis (failure to develop ovaries)
Chromosomal abnormality, such as Turner’s syndrome
Ovarian steroidogenesis defect, such as 17 alpha hydroxylase deficiency
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.
Gonadal agenesis (failure to develop testes)
Chromosomal abnormality, such as Klinefelters syndrome
Viral infection (mumps)
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.
This article was last reviewed on 10 September 2015. | This article was last modified on 14 September 2015.
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