To Örebro University

Introduction: Kisspeptin stimulates the gonadotropin releasing hormone (GnRH) neurons in hypothalamus initiating puberty. However, it is not known whether GnRH inhibits kisspeptin secretion by negative feedback and whether there are any associations between circulating levels of kisspeptin and other hormones, like ghrelin, important for the onset of puberty.

Methods: Thirteen girls with suspected central precocious puberty performed an adjusted GnRH stimulation test twice, placebo-controlled in a randomized order, at Örebro or Uppsala University Hospital, Sweden. Blood was sampled 0, 30, 60, 90, 120 and 150 min after the iv injection of either Relefact LHRH® or saline. The protease inhibitor 4-(2-aminoethyl) benzenesulfonyl fluoride hydrochloride (AEBSF) was added to the sampling tubes to a final concentration of 2 mg/ml. An ELISA kit from LifeSpan BioSciences, Inc. (No LS-F8231) was used for the analyses of Kisspeptin-1 levels. The levels of acylated ghrelin were analyzed with Millipore® Human Ghrelin (Active) ELISA kit (#EZGRA-88K). Serum ultrasensitive estradiol, luteinizing hormone (LH), follicle-stimulating hormone (FSH), insulin and glucose levels were analyzed using the usual clinical methods.

Results: The median Kisspeptin-1 level at baseline was 39 pg/ml (min–max: 0.1–221.3 pg/ml). The area-under-the curve for Kisspeptin-1 levels was not significantly lower after the GnRH injection as compared to the placebo injection. We did not find any significant correlations between the levels of kisspeptin-1 and acylated ghrelin, estradiol, LH, FSH, or insulin. However, we could see a positive correlation between kisspeptin-1 and glucose levels at baseline (Spearman’s rank test, rho = 0.63, p=0.021).

Discussion: We did not find evidence of a negative feedback mechanism between GnRH and kisspeptin in girls with suspected central precocious puberty since the circulating levels of kisspeptin-1 were unaffected by an intravenous injection of a GnRH analogue. However, paracrine actions in the hypothalamus cannot be ruled out by this study. The positive correlation found between kisspeptin-1 and glucose levels is in accordance with previous findings in both adults and children, suggesting a possible role for kisspeptin signaling in glucose metabolism.