Divergent responses to kisspeptin in children with delayed puberty

Abstract

Background: The neuropeptide kisspeptin stimulates luteinizing hormone (LH) secretion in healthy adults but not in adults with idiopathic hypogonadotropic hypogonadism. We hypothesized that, in children presenting with delayed or stalled puberty, kisspeptin would elicit LH secretion in those children found on detailed nighttime neuroendocrine profiling to have evidence of emerging reproductive endocrine function.

Methods: Eleven boys and four girls were admitted overnight to assess LH secretion at baseline, after a single intravenous bolus of kisspeptin, and after a single intravenous bolus of gonadotropin-releasing hormone (GnRH). Subjects then received exogenous pulsatile GnRH for 6 days and returned for a second visit to measure responses to kisspeptin and GnRH after this pituitary "priming." Responses to kisspeptin and GnRH were also measured in 5 healthy men.

Results: Of the 15 children with delayed/stalled puberty, 6 exhibited at least one spontaneous LH pulse overnight; all of these subjects had clear responses to kisspeptin, as did one additional subject. Seven subjects had no response to kisspeptin, and one subject exhibited an intermediate response. In the children who responded to kisspeptin, the responses had features comparable to those of adult men.

Conclusion: In this first report of kisspeptin administration to pediatric subjects to our knowledge, children with delayed/stalled puberty showed a wide range of responses, with some showing a robust response and others showing little to no response. Further follow-up will determine whether responses to kisspeptin predict future pubertal entry for children with delayed puberty.

Trial registration: ClinicalTrials.gov NCT01438034 and NCT01952782.

Funding: NIH Eunice Kennedy Shriver National Institute of Child Health and Human Development (R01 HD043341, R01 HD090071, P50 HD028138), NIH National Center for Advancing Translational (UL1 TR001102), NIH National Institute of Diabetes and Digestive and Kidney Diseases (T32 DK007028), the Massachusetts General Hospital Executive Committee on Research Fund for Medical Discovery, Harvard Catalyst, Doris Duke Charitable Foundation (award 2013110), Charles H. Hood Foundation, Robert and Laura Reynolds MGH Research Scholar Program, and Harvard University. These funding sources had no role in the design of this study and did not have any role in conducting the study, analyses, interpretation of the data, or the decision to submit results.

Keywords: Neuroendocrine regulation; Reproductive Biology.

Conflict of interest statement

Conflict of interest: YMC was a member of the scientific advisory board for AbbVie.

Figures

Figure 1. Summary of recruitment.

Figure 2. Protocol schematic.

Subjects underwent two visits to the Clinical Research Center. During the first visit, blood was drawn every 10 minutes to measure luteinizing hormone (LH) at baseline (from 2–8 am), after an intravenous bolus of kisspeptin, and after an intravenous bolus of gonadotropin-releasing hormone (GnRH). Subjects then underwent pituitary “priming” with exogenous GnRH and then returned for a second visit to measure LH after boluses of kisspeptin and GnRH. IV, intravenous; SC, subcutaneous; q2h, every 2 hours.

Figure 3. Neuroendocrine profiles of subjects with robust responses to kisspeptin.

Serum luteinizing hormone (LH) concentrations were measured at baseline (hours 0–6), after exogenous kisspeptin (hours 6–10), and after exogenous gonadotropin-releasing hormone (GnRH; hours 10–11). Subjects returned after priming with exogenous GnRH, and serum LH was measured at baseline (hours 0–1), after exogenous kisspeptin (hours 1–5), and after exogenous GnRH (hours 5–6). Baseline concentrations of serum sex steroids (estradiol and testosterone) were determined by measuring pools of samples collected between 0 and 2 hours, 2 and 4 hours, and 4 and 6 hours during the visit before priming and of samples collected between 0 and 1 hour in the visit after priming. (A) A representative “responder” (1 of 7) who before priming demonstrated an endogenous LH pulse, a clear response to kisspeptin, and a robust response to GnRH and after priming demonstrated little change in the responses to kisspeptin and GnRH. (B) A “responder” who did not exhibit baseline LH pulses, most likely because he had recently received a dose of exogenous testosterone and the resulting high serum testosterone suppressed endogenous LH secretion. Note that the response to kisspeptin was still robust.

Figure 4. Neuroendocrine profiles of subjects whose responses to kisspeptin were absent or small.

(A) A representative “nonresponder” (1 of 7) who demonstrated no endogenous luteinizing hormone (LH) pulses, no response to kisspeptin (before or after priming), and a small response before priming to gonadotropin-releasing hormone (GnRH) that was augmented by priming with repeated doses of exogenous GnRH. (B) An intermediate response to kisspeptin in a subject whose baseline LH was measurable but apulsatile and who had a robust response to exogenous GnRH even before priming.

Figure 5. Magnitude of responses to kisspeptin in pediatric subjects and adult subjects.

To estimate the response of gonadotropin-releasing hormone (GnRH) neurons to kisspeptin and to account for potential differences in pituitary responsiveness to GnRH, the amplitude of kisspeptin-induced luteinizing hormone (LH) pulses (ΔLHkisspeptin) was normalized to the amplitude of GnRH-induced LH pulses (ΔLHGnRH), and the ratios between these two amplitudes (ΔLHkisspeptin/ΔLHGnRH) are shown. Bars show means and standard deviations. No significant differences were observed between groups with unpaired t tests. n = 15 total pediatric subjects, 7 responders; n = 5 adult subjects.