GH1 and major depressive disorder: Moreover, there is indirect neuroendocrine evidence for altered 5-HT1B receptor function in MDD, with blunted growth hormone (GH) response to the 5-HT1B/1D receptor agonist sumatriptan in MDD patients (Cleare et al. 1998) and likewise reduced GH response to another triptan, zolmitriptan, which passes the blood brain barrier to a higher degree than sumatriptan, in a subpopulation of MDD patients with melancholic depression (Whale et al. 2001).