APPLICATION: Investigation of gonadal hypofunction, suspected pituitary tumour.
INTERPRETATION: Levels of follicle stimulaing hormone (FSH) are increased when pituitary secretion occurs in the absence of feedback inhibition by the gonadal androgens or oestrogens: primary gonadal hypofunction, post-menopausal state, castration. Increased levls may also be seen with pituitary gonadotroph tumours, although some tumors secrete only the alpha subunit. Levels are decreased if ovarian or testicular failure is due to pituitary or hypothalmic disease.