Invest Clin 60(4): 310 - 318, 2019 https://doi.org/10.22209/IC.v60n4a05 Corresponding author: Mudhafar Mohamed M. Saeed, College of Pharmacy, Hawler Medical University, Erbil, Kurd- istan region, Iraq. Email: Mudhafar.pharm@gmail.com The effects of vitamin D supplementation on endogen amylin hormone, hormonal and biochemical parameters, and insulin resistance in type-2 diabetic patients with vitamin D deficiency in the Kurdistan Region of Iraq. Mudhafar Mohamed M. Saeed 1 , Abdulqader Azeez Al-Naqshabandi 1 and Hawri Fatih Sami Aldawoodi 2 1 College of Pharmacy, Hawler Medical University, Erbil, Kurdistan region, Iraq. 2 Department of Biology, College of Science,Cihan University, Erbil, Kurdistan region, Iraq. Key words: vitamin D; amylin; HbA1c; insulin; C-peptide. Abstract. The present study was conducted to evaluate the correlations between vitamin D, amylin, c-peptide, insulin, and HbA1c and determine the effects of vitamin D supplementation on the level of these biomarkers in type-2 diabetic patients with vitamin D deficiency. A total of 87 Kurdish type-2 dia- betic patients participated in this clinical trial in which biomarkers, including vitamin D (25 hydroxy cholecalciferol), serum amylin, c-peptide, insulin, fast- ing blood glucose, HbA1c, HDLc, LDLc, total cholesterol, triglycerides, weight, height, waist circumference, and inflammation markers (i.e. IL6, TNF-α, and hs- CRP) were measured. Serum levels of vitamin D were positively correlated with serum Amylin, c-peptide, insulin, and HDL, while it had negative correlations with HbA1c, fasting blood sugar, IL6, TNF-α, hs-CRP, LDL, and triglycerides. After 14 weeks of supplementation with vitamin D (5000 IU/day) there were significant increases in plasma amylin, c-peptide, and insulin concentrations; but the levels of HbA1c, fasting blood glucose, TNF-α, hs-CRP, and IL6 were significantly decreased. It can be concluded that vitamin D supplementation can potentially regulate blood glucose by activating the secretory function of pancreatic B-cells and reducing insulin resistance through a significant reduc- tion in a circulatory level of inflammatory markers.