In a small study, the synthetic peptide hexarelin raised growth hormone (GH) levels in both women with high prolactin and healthy controls, but it also caused a slight increase in prolactin. The dopamine‑activating drug bromocriptine lowered prolactin and boosted GH, and when given before hexarelin it stopped the prolactin rise in the high‑prolactin group and only reduced it in controls. This shows hexarelin can act as a modest GH secretagogue, but its prolactin‑raising side effect may need to be managed.

Hexarelin (Hex), a synthetic GH-releasing peptide, has recently been found to possess a weak PRL-releasing effect in normals. The aims of this study were to investigate the effect of Hex on GH and PRL secretion in 10 hyperprolactinemic women (HPRL) and 7 controls (C). All subjects underwent stimulus testing with placebo, bromocriptine (Br) (2.5 mg po at time -60), Hex (2 micrograms/kg/bw i.v.), and Br plus Hex. During placebo, HPRL showed a higher (p < 0.01) PRL area under curve (AUC) than C. Br significantly (p < 0.01) reduced PRL AUC both in HPRL and in C. Hex was able to induce a slight but significant (p < 0.05) PRL release in both groups. PRL response to Hex was abolished (p < 0.01 vs Hex) by Br priming in HPRL, while it was only blunted (p < 0.05 vs Hex) in C. Br induced a significant (p < 0.01) GH increase in both groups. However, GH AUC after Br was significantly higher (p < 0.01) in C than HPRL. Hex induced a significant (p < 0.01) GH release both in HPRL and in C. Br priming did not modify GH response to Hex in HPRL while it slightly (p < 0.05) increased GH response to Hex in C, suggesting that neuroendocrine modifications present in HPRL might, per se, be able to impair GH response to Br plus Hex, thus giving rise to receptor competition. Hex had a weak PRL-releasing effect in both groups studied, this was only blunted by Br priming in C but was abolished in HPRL, suggesting that oversensitivity to DA-ergic agents present in HPRL could be able to antagonize completely Hex action.