ناهضات مستقبِل هرمون محرِّر الغونادوتروبين

The GnRH receptor is a G protein-coupled receptor on the pituitary gonadotroph; GnRH binding couples it to G proteins that activate a phosphatidylinositol-calcium second messenger system, stimulating secretion of luteinising hormone and follicle-stimulating hormone. Drugs in this class activate that receptor, and the exposure pattern decides the direction of the result. A single dose acts like the natural pulse: the label for gonadorelin in cattle states that it initiates release of endogenous LH to cause ovulation and luteinisation. Sustained exposure does the opposite: the leuprolide label records an initial increase in circulating LH and FSH but states that continuous daily administration then results in decreased LH and FSH, and that in animal studies continuous administration produces suppression of ovarian and testicular steroidogenesis after an initial stimulation. The deslorelin slow-release implant is labelled accordingly as suppressing the reproductive endocrine system and preventing production of pituitary and gonadal hormones.