LH ASSAY - A blood test which measures the amount of luteinizing hormone (LH). LH is a protein hormone that is secreted by the anterior pituitary gland. In women, a surge in LH at midcycle causes ovulation. For the next 7-10 days LH maintains the corpus luteum which synthesizes progesterone. The corpus luteum disintegrates after about 10 days if fertilization does not occur. In men, LH stimulates production of testosterone by the Leydig cells in the testes. This test may be used to evaluate anovulatory bleeding, infertility, ovarian cysts, and multiple endocrine neoplasia (MEN) I. Normal values in males: 7 to 24 U/L. Normal values in females: greater than 6-30 U/L. Greater than normal values can indicate: anorchia, hypogonadism, Klinefelter's syndrome, menopause, ovarian failure, polycystic ovary disease, precocious puberty, and Turner's syndrome. Lower than normal values can indicate hypopituitarism.