LH is often used in conjunction with other tests (FSH, testosterone, oestradiol and progesterone) in the investigation of infertility in both men and women. LH 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 and precocious (early) puberty.
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
Premature ovarian failure due to:
Chronic anovulation (failure to ovulate) due to:
When a woman enters the menopause and her ovaries stop working, FSH and LH levels will rise.
Low levels of FSH and LH are consistent with secondary ovarian failure due to a pituitary or hypothalamic problem.
In men, high FSH levels are due to primary testicular failure. This can be due to developmental defects in testicular growth or to testicular injury, as indicated below.
- Gonadal agenesis (failure to develop testes)
- Chromosomal abnormality, such as Klinefelter's syndrome
Low levels of FSH are consistent with pituitary or hypothalamic disorders.
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.
LH results can be increased with use of certain drugs, such as clomiphene and naloxone. LH results can decrease with oral contraceptives (the pill), phenothiazines and certain hormone treatments.