What is being tested?Luteinizing hormone (LH) is produced by the pituitary gland in the brain. Control of LH production is a complex system involving
hormones produced by the gonads (ovaries or testes), the pituitary, and the hypothalamus.
Women’s menstrual cycles are divided into 2 phases, the follicular and luteal, by a mid-cycle surge of
follicle-stimulating hormone (FSH) and LH. The high level of LH (and FSH) at mid-cycle triggers ovulation. LH also stimulates the ovaries to produce steroids, primarily estradiol. Estradiol and other steroids help the pituitary to regulate the production of LH. At the time of
menopause, the ovaries stop functioning and LH levels rise.
In men, LH stimulates the Leydig cells in the testes to produce testosterone. LH levels are relatively constant in men after puberty. Testosterone provides negative feedback to the pituitary and the hypothalamus, helping to regulate the amount of LH secreted.
In infants and children, LH 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 before 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 in the arm. Sometimes, a
random urine sample is used. A
24-hour collection of urine may be requested if your doctor wants to measure LH levels produced over a 24-hour period. LH is released intermittently throughout the day and a 24-hour urine collection eliminates problems due to that variation. A random sample might not show the actual activity of the hormone.
