Follicle-stimulating hormone (FSH) is made by the pituitary gland in the brain. The production and release of FSH and LH in the pituitary gland is stimulated by gonadotrophin releasing hormone (GnRH) present in the hypothalamus. Control of FSH and LH production is a complex feedback system being regulated by oestradiol from the ovaries or testosterone from the testes. In women, FSH stimulates the growth and development of ovarian…Follicle-stimulating hormone (FSH) is made by the pituitary gland in the brain. The production and release of FSH and LH in the pituitary gland is stimulated by gonadotrophin releasing hormone (GnRH) present in the hypothalamus. Control of FSH and LH production is a complex feedback system being regulated by oestradiol from the ovaries or testosterone from the testes. In women, FSH stimulates the growth and development of ovarian follicles (unfertilised 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 the menopause, the ovaries stop functioning and FSH levels rise. During pregnancy, oestrogen levels are high and this makes FSH undetectable. 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. How is the sample collected for testing? A blood sample is taken by needle from a vein, normally in the arm. Is any test preparation needed to ensure the quality of the sample? No, but in a woman, the sample should be taken in the first 4 days of her cycle if the periods are regular (day 1 is the first day of full bleeding). If the test is for the menopause, for example, and periods are stopping then the FSH can be taken at any time but occasionally repeat samples may be needed. This is because it can take a couple of years for the ovaries to stop working completely and results may be contradictory when the menopause first starts to occur. It is important to note that the test should not be performed if a woman is taking female hormones (for example contraceptives such as the combined oestrogen and progestogen or high-dose progestogen pill) as this will affect the interpretation of results. See MoreSee Less
