Effect of gonadotropin‐inhibitory hormone on luteinizing hormone secretion in humans

Summary Background Gonadotropin‐inhibitory hormone (GnIH, human homologue of RFRP‐3) suppresses gonadotropin secretion in animal models, but its effects have not been studied in the human. Objective We tested the hypotheses that exogenous GnIH inhibits LH secretion (i) in postmenopausal women and (ii) in men concurrently administered exogenous kisspeptin. Design Following in vitro and in vivo preclinical studies to functionally characterize the GnIH peptide, a dose‐finding study (human GnIH: 1·5–150 μg/kg/h, iv for 3 h) was undertaken, and 50 μg/kg/h selected for further evaluation. Five postmenopausal women were administered 50 μg/kg/h iv infusion for 3 h or vehicle on two separate days. Four men were administered kisspeptin‐10 (0·3 μg/kg iv bolus) with simultaneous infusion of GnIH (50 μg/kg/h, iv for 3 h) or vehicle. Participants Healthy postmenopausal women (mean age 58 ± 2 years, LH: 30·8 ± 2·9 IU/l, FSH: 78·7 ± 6·4 IU/l, oestradiol: