en Endocrinology Endocrinology Original Article Original Article <span style="font-size:14px;"><span style="font-family:Times New Roman;"><span style="color:#0000ff;"><strong><em>Background</em></strong><em>:</em> </span>Hyperglycemia is a common finding which is associated with increased mortality and morbidity among critically ill patients. There is currently no evidence that melatonin could improve stress induced hyperglycemia (SIH). In this study, we evaluated the effect of melatonin on blood sugar and insulin resistance (IR) in critically-ill patients.<br> <span style="color:#0000ff;"><strong><em>Methods</em></strong><em>:</em> </span>104 critically-ill patients with SIH divided into two groups, receiving melatonin (6 mg BD for 3 days) or placebo. Changes of blood sugar, IR indices including homeostasis model assessment for insulin resistance and homeostasis model assessment adiponectin (HOMA-AD) ratios, Glasgow coma scale (GCS) were evaluated on the 4^th day of melatonin prescription. On the 7^{Th day}of study, changes of ventilator dependency and delirium were considered. Mortality and intensive care unit (ICU) stay were also compared between groups.<br> <span style="color:#0000ff;"><strong><em>Results</em></strong><em>:</em></span> On day 4, patients in the melatonin group had significantly lower blood glucose and HMOA-IR level compared with the placebo group (P=0.04 and P=0.03, respectively) whereas HOMA-AD level did not differ significantly from placebo group (p>0.2). Also, we did not observe any significant difference in GCS level at this time between groups (p>0.2). On day 7, melatonin could not improve ventilator dependency and delirium significantly (p>0.2) and also could not reduce mortality and ICU stay in comparison with placebo (p>0.2, P=0.2, respectively).<br> <span style="color:#0000ff;"><strong><em>Conclusion</em></strong><em>:</em></span> Melatonin supplementation showed positive effect on blood sugar and somehow insulin resistance whereas it could not improve ICU complications.</span></span> stress induced hyperglycemia, insulin resistance, Melatonin, APACHE II, ICU 51 60 http://caspjim.com/browse.php?a_code=A-10-2077-1&slc_lang=en&sid=1 Fahimeh Naderi-Behdani fahime.naderi90@gmail.com 100319475328460033306 100319475328460033306 No Department of Clinical Pharmacy, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran Fatemeh Heydari fateme58@yahoo.com 100319475328460033307 100319475328460033307 No Department of Anesthesiology and Critical Care Medicine, Imam Khomeini Hospital, Mazandaran University of Medical Sciences, Sari, Iran shahram Ala sh204ala@gmail.com 100319475328460033308 100319475328460033308 Yes Department of Clinical Pharmacy, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran Siavash Moradi d.smor86@yahoo.com 100319475328460033309 100319475328460033309 No Educational Development Center, Mazandaran University of Medical Sciences, Sari, Iran Saeid Abediankenari abedianlab@yahoo.co.uk 100319475328460033310 100319475328460033310 No Department of Immunology, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran Hosein Asgarirad dr_asgarirad@yahoo.com 100319475328460033311 100319475328460033311 No Department of Pharmaceutics, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran Elmira khodabakhsh khodabakhsh64@gmail.com 100319475328460033312 100319475328460033312 No Department of General Surgery, Imam Khomeini Hospital, Mazandaran University of Medical Sciences, Sari, Iran