Figure 1. Experimental protocol and effects of kisspeptin administration on hormone levels.

Twenty-nine healthy young men participated in a randomized, double-blinded, 2-way crossover, placebo-controlled study. They participated in 2 study visits: one for intravenous administration of kisspeptin (1 nmol/kg/h) and one for intravenous administration of an equivalent volume of vehicle for 75 minutes. Participants completed baseline and intrainfusion questionnaires (Q) and underwent functional MRI scanning while performing image tasks (see Methods). (A) Kisspeptin infusion resulted in increased circulating kisspeptin levels reaching a plateau at 30 minutes after initiation. Therefore, there were stable circulating kisspeptin levels during the fMRI and intrainfusion psychometric assessments (n = 29). (B) In parallel, kisspeptin increased circulating LH levels (n = 29). (C–E) Kisspeptin had no effect on circulating testosterone (n = 29), oxytocin (n = 13), or cortisol levels (n = 29). Data depict mean ± SEM. ****P < 0.0001, 2-way ANOVA.