The study looked at whether giving GnRH to young girls changes their kisspeptin levels. It found no clear drop in kisspeptin after GnRH, and kisspeptin levels varied a lot between individuals. A possible link between kisspeptin and blood sugar was hinted but not proven.

Kisspeptin plays a major role in the onset of puberty by stimulating the gonadotropin-releasing hormone (GnRH) neurons. The aim of this study was to investigate whether GnRH inhibits kisspeptin secretion via a negative feedback mechanism and potential associations between kisspeptin levels and other hormones of importance for pubertal onset. Thirteen girls with suspected central precocious puberty underwent a GnRH stimulation test twice in a randomized, placebo-controlled manner. Blood was sampled up to 150 min after an IV injection of either Relefact LHRH^® or saline. The levels of kisspeptin, acylated ghrelin, ultrasensitive oestradiol, luteinizing hormone (LH), follicle-stimulating hormone (FSH), insulin and glucose were analysed. Baseline kisspeptin levels ranged from 9.9 to 201.6 pg/mL. Neither area under the curve for kisspeptin levels nor peaks were significantly lower after the GnRH injection compared to placebo. Baseline kisspeptin and glucose levels tended to be associated (rho=0.55, p=0.051) but no other associations were found between kisspeptin and other hormones. Basal levels of kisspeptin vary widely in young girls. We found no evidence of a negative feedback mechanism of GnRH on kisspeptin in this small pilot study. The suggested association between kisspeptin and glucose levels needs further investigations.