LH

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 (release of the egg from the ovary). LH also stimulates the ovaries to produce other hormones, mainly oestradiol. Oestradiol helps the pituitary gland to control the production of LH. At the time of the 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.

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 with the beginning of puberty and the development of secondary sexual characteristics.