What is being tested?Follicle-stimulating hormone (FSH) is made by the pituitary gland in the brain. Control of FSH production is a complex system involving
hormones produced by the gonads (ovaries or testes), the pituitary gland, and the hypothalamus, such as gonadotrophin-releasing hormone (GnRH).
In women, FSH stimulates the growth and develpoment of ovarian follicles (eggs) during the follicular phase of the menstrual cycle. This cycle is divided into two phases, the follicular and the luteal, by a mid-cycle surge of FSH and
luteinising hormone (LH). Ovulation (release of the egg from the ovary) occurs shortly after this mid-cycle surge of hormones. During the follicular phase, FSH initiates the production of oestradiol by the follicle, and the two hormones work together in the further development of the egg follicle. During the luteal phase, FSH stimulates the production of progesterone. Both oestradiol and progesterone help the pituitary control the amount of FSH produced. At the time of
menopause, the ovaries stop functioning and FSH levels rise.
In men, FSH stimulates the testes to produce mature sperm. FSH levels are relatively constant in men after puberty.
In infants and children, FSH 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.
