Growth hormone, cortisol and prolactin responses to physical exercise: higher prolactin response in depressed patients Evelyn Kiive a , Jaak Maaroos b , Jakov Shlik c , Innar To˜ru c , Jaanus Harro a, * a Department of Psychology, Centre of Behavioural and Health Sciences, University of Tartu, Tiigi 78, Tartu, 50410, Estonia b Department of Sports Medicine and Rehabilitation, University of Tartu, Puusepa 6, Tartu, 51014, Estonia c Department of Psychiatry, University of Tartu, Raja 31, Tartu, 50417, Estonia Accepted 10 May 2004 Available online 6 August 2004 Abstract This study was designed to compare growth hormone, cortisol and prolactin responses to physical exercise in depressed patients and healthy comparison subjects. Patients fulfilled the DSM-IV diagnostic criteria for current major depressive disorder; subjective depressive symptoms were rated with Montgomery-2sberg Depression Rating Scale (M2DRS) immediately before the experiment. Growth hormone, cortisol and prolactin were measured before and immediately after physiologically stressful bicycle cardiopulmonary exercise test. After exercise, there were three additional hormone measurements, with 30-min intervals. No significant difference was found in baseline growth hormone, cortisol or prolactin levels between patients and the control group. Plasma growth hormone and cortisol levels increased significantly during physical exercise in both patients and controls and returned to baseline in 90 min. There was no significant difference in growth hormone or cortisol responses to physical exercise between the two groups. However, prolactin levels increased only in the depressed patients group during the exercise. We hypothesize that acute exercise may have a stronger effect on serotonin (5-HT) release in depressed patients, which is reflected in increased plasma prolactin concentration. D 2004 Elsevier Inc. All rights reserved. Keywords: Cortisol; Depression; Growth hormone; M2DRS; Physical exercise; Prolactin 1. Introduction Numerous endocrine abnormalities have been described in depressive illness. Patients show increased plasma cortisol levels and blunted growth hormone and prolactin release in pharmacological challenge tests. Abnormality of the hypothalamic-pituitary-adrenal (HPA) axis has been one of the most consistently demonstrated biological alterations in depressive disorder. A significant proportion of patients with major depression hypersecrete cortisol (Dinan, 1994) and cortisol levels often remain elevated throughout the day with an absence of normal diurnal variation (Sachar et al., 1973). A number of authors have proposed that increased cortisol secretion down-regulates serotonin (5-HT) neuro- transmission which leads to clinical depression in vulnerable individuals (Deakin and Graeff, 1991; Dinan, 1994). Depressives have a dysfunction in the 5-HT 1A receptor activity, which could be due to a hypersecretion of cortisol (Pitchot et al., 2001). The regulation of the release of prolactin also involves the monoamine neurotransmitter systems that have been impli- cated in the pathophysiology of depression. Fenfluramine- induced release of 5-HT in the hypothalamus causes the release of prolactin and the prolactin response is used as an index of central 5-HT function (Siever et al., 1984; Mann, 1999). The prolactin response to a challenge dose of fenfluramine is attenuated in patients with affective or personality disorders (Coccaro et al., 1989). The interindi- 0278-5846/$ - see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.pnpbp.2004.05.035 Abbreviations: GHRH, Growth hormone releasing hormone; HPA, hypothalamic-pituitary-adrenal; M2DRS, Montgomery-2sberg Depression Rating Scale; 5-HT, serotonin. * Corresponding author. Tel.: +372 7 375911; fax: +372 7 375900. E-mail address: jaanus.harro@ut.ee (J. Harro). Progress in Neuro-Psychopharmacology & Biological Psychiatry 28 (2004) 1007 – 1013 www.elsevier.com/locate/pnpbp