Continuous kisspeptin-10 infusion dynamically modulates LH secretion in healthy men, initially boosting then partially desensitizing.
Background
The hypothalamic-pituitary-gonadal (HPG) axis is critically regulated by gonadotropin-releasing hormone (GnRH), which in turn is stimulated by kisspeptin. While kisspeptin is known to trigger gonadotropin secretion, continuous administration has shown to dampen GnRH release in non-human primates, a phenomenon not yet clearly replicated in humans. Understanding this dynamic is crucial for therapeutic applications targeting infertility or hypogonadism, as current approaches often involve pulsatile or bolus dosing. This study aimed to clarify the effects of sustained kisspeptin exposure on luteinizing hormone (LH) secretion in healthy men.
Study Design
Three healthy adult men received a continuous intravenous infusion of kisspeptin-10 at a dose of 12.5 mcg/kg/h for 24 h. Throughout the infusion, frequent blood sampling was conducted to characterize the dynamic effects on reproductive hormones. The primary endpoint was the change in LH concentrations, with secondary assessments of FSH and testosterone levels. This design allowed for the observation of both initial stimulatory and potential desensitization phases without a separate control arm, using baseline levels as internal controls.
Results
Continuous administration of kisspeptin-10 led to an immediate and significant increase in LH concentrations. Baseline LH levels of 2.8-3.8 mIU/mL surged to peak values of 17.5-30.6 mIU/mL, representing a 5- to eightfold increase above baseline. These peak levels were typically reached within 12-20 h of infusion onset. Following this initial robust stimulation, LH concentrations subsequently declined.
LHlevels decreased by 13-47% from their maximum values by the end of the 24-hour infusion, settling at 10.7-22.8 mIU/mL. This indicates a dynamic modulation rather than sustained maximal stimulation.FSHandtestosteronelevels also showed modest increases in parallel withLHchanges, supporting the activation of the downstreamHPG axis.
Key Findings
- Continuous kisspeptin-10 infusion increased LH concentrations 5- to eightfold above baseline.
- Peak LH levels of 17.5-30.6 mIU/mL were reached within 12-20 h of infusion onset.
- LH concentrations subsequently declined by 13-47% from their maximum by the end of the 24-hour infusion.
- Final LH levels settled at 10.7-22.8 mIU/mL after the decline.
- FSH and testosterone levels showed modest parallel increases.
Why It Matters
This study provides critical insights into the dynamic responsiveness of the HPG axis to sustained kisspeptin stimulation in men. Understanding the biphasic response—initial robust stimulation followed by partial desensitization—is vital for optimizing kisspeptin-based therapies for conditions like hypogonadism or fertility issues. For peptide users and clinicians, this suggests that continuous infusion protocols might need careful titration or pulsatile delivery to avoid receptor desensitization and maintain optimal LH and testosterone levels. It highlights that the mode of administration (bolus vs. continuous) significantly impacts the physiological outcome, offering a new tool for studying GnRH-induced LH secretion dynamics beyond simple bolus challenges.
kisspeptin
lh
gnrh
hpta-axis
men's-health
fertility