Effect of galanin on basal and stimulated secretion of prolactin, gonadotropins, thyrotropin, adrenocorticotropin and cortisol in humans

Abstract

Arvat E, Gianotti L, Ramunni J, Grottoli S, Brossa PC, Bertagna A, Camanni F, Ghigo E, Effect of galanin on basal and stimulated secretion of prolactin, gonadotropins, thyrotropin, adrenocorticotropin and cortisol in humans. Eur J Endocrinol 1995;133:300–4. ISSN 0804–4643. Galanin enhances both baseline and growth hormone-releasing hormone (GHRH)-induced GH secretion both in animals and in man. Although galanin has a clear influence on the secretion of other anterior pituitary hormones in animals, in man it increases prolactin (PRL) slightly but does not affect spontaneous thyrotropin (TSH), luteinizing hormone (LH), follicle-stimulating hormone (FSH) or adrenocorticotropin (ACTH) secretion. The aim of our study was to verify the effect of galanin on basal and releasing hormone-stimulated release of gonadotropins, PRL, TSH, ACTH and cortisol secretion. As GH release has been shown to be inhibited by corticotropin-releasing hormone (CRH), we also studied the effect of CRH on galanin-stimulated GH increase. The effect of porcine galanin (15 μg/kg iv infused in 60 min) alone and in combination with thyrotropin-releasing hormone (TRH, 200 μg iv bolus), CRH (100 μg iv bolus) and gonadotropin-releasing hormone (GnRH, 100 μg iv bolus) on GH, PRL, TSH, ACTH, cortisol, FSH and LH secretion in seven normal young women (aged 25–30 years) was studied. Galanin infusion caused an increase in serum GH levels (p < 0.02) but failed to modify significantly the spontaneous PRL, LH, FSH, TSH, ACTH and cortisol secretion. The combined administration of TRH, GnRH and CRH caused a significant increase in PRL (p < 0.02), LH (p < 0.02), FSH (p < 0.02), TSH (p < 0.02), ACTH (p < 0.02) and cortisol (p < 0.05), but not in GH levels. Galanin infusion significantly enhanced the PRL response to TRH + GnRH + CRH administration (p < 0.05), while the releasing hormone-stimulated levels of LH, FSH, TSH, ACTH and cortisol were not influenced by galanin. The GH release after the combined administration of GAL, TRH, GnRH and CRH was similar to that observed after galanin alone. In conclusion, the present results support the view that galanin plays a role in the control of GH and PRL secretion in humans. On the other hand, galanin does not seem to have any influence on the secretion of the other pituitary hormones in humans. However, a role for galanin in the modulation of hypophysiotropic neurohormone function at the hypothalamic level cannot be ruled out. Ezio Ghigo, Divisione di Endocrinologia, Ospedale Molinette. Corso Dogliotti 14, 10126 Torino, Italy