x-squared= 4.0645 p= 0.255 /10 patients had no pathology results Methodology An observational retrospective cohort study. King Abdulaziz University Hospital (KAUH)’s thyroid database was used to extract data from 1008 patients who were referred to the head & neck oncology clinic at 2 centers (KAUH & King Fahad Medical City) starting January 2011, including: their co-morbidities, type of surgery, 25(OH)vitD levels and final pathological diagnosis (benign/ malignant). 201 patients were excluded due to unavailable pre-op vit.D levels. Cohort was divided according to vitD category (30 nmol/L or less, >30 to 50, >50 to 100, >100) Patients’ final diagnosis was compared to their pre-op vitD levels using a two sample t-test with welch’s modification. Patients’ final diagnosis was also compared to their vitD category using Pearson-Chi square test. Results Our final cohort consisted of 807 patients of which 167 were male and 640 were female. Summary of their characteristics shown inTable-1 Diabetic patients had significantly higher levels of vitamin D with a mean of 52.6nmol/L vs. 41nmol/L in non-diabetics (p=0.0001) The final histopathological diagnosis was benign in 402 patients and malignant in 395. (table-2) Our data showed no correlation between vit.D values and diagnosis with malignant disease (mean: 41.9 nmol/L in benign group vs 44.4 nmol/L in malignant group , p=0.1007, CI: -7.067, 0.626) neither with specific vit.D categories (table-2) After isolating patients who received vit.D supplementation, statistical analysis didn’t show any significant correlation between supplementation and incidence of thyroid malignancy. Diabetic patients in general had significantly higher levels of vit.D and were more likely to be category III. This finding could be explained by frequent visits and follow up with their endocrinologist or family physician. In addition, patients receiving vitamin D supplements as expected had significantly higher vitamin D levels (mean: 74 nmol/L vs. 41.6 nmol/L p=0.0001) Unlike some recently published data that showed promising results, we were not able to find any correlation between vit D and thyroid cancer.(5) Although vitamin D supplementation was associated with better vitamin D levels, it didn’t show any protective effect against thyroid cancer. Vitamin D levels: A Potential Modifiable Risk Factor For Thyroid Malignancy? Aldhahri, Fahad S*; Aldhahri, Saleh F**; Alessa, Mohammed A***; Alghammass, Mohammed A* * Medical student ** Associate professor of Otolaryngology *** Assistant professor of Otolaryngology Introduction Thyroid cancer is the most common endocrine malignancy worldwide. It is the 2nd most common cancer amongst Saudi women.(1) Incidence in Saudi : 800 cases in 2011.(1) A 2012 Saudi study showed that 87.8% of Saudis are vitamin D (vit.D) deficient(<50 nmol/L).(2) Several studies were published on vit.D’s relation to different cancers. Institute Of Medicine declared current available data inconclusive. (4) Several observational studies done on vit.D and thyroid cancer: small sample sizes, use of different exposures and cutoff levels of 25(OH)vitD  caused the results of these studies to be varying, not possible to undergo pooling analysis and eventually unsatisfying Conclusion Our study was not able to show a correlation between vit.D levels and thyroid malignancy. Vitamin D supplementation didn’t show any protective effect against thyroid ca in our cohort. The study was limited by being retrospective and hospital based. Table -1 Table -2 Patients’ characteristics Frequency (%) Gender Male (mean age: 43.8 y/o) Female (mean age: 40.9 y/o)   167 (21) 640 (79) Diabetes Mellitus? No 670 (83) Yes 136 (17) BMI <18.5 17(2) 18.5-25 153(19) >25-29.9 218(27) >30 419(52) Vitamin D category: I: 0-30 nmol/L 349 (43) II: 30-50 nmol/L 191 (24) III:50-100 nmol/L 236 (29) IV: >100 nmol/L 31 (4) Pre-op vitamin D use? No 443 (55) 58 (7) Unavailable 306 (38) VitD category Benign Malignant Total < 30 nmol/L 184 164 348 30-50 nmol/L 96 92 188 50-100 nmol/L 111 119 230 >100 nmol/L 11 20 31 402 395 797 x-squared= 4.0645 p= 0.255 /10 patients had no pathology results Discussion In consistency with previously published data, the largest proportion of thyroid patients in our sample were female(79%) and had a BMI > 30 (52%). (3) Saudi Cancer Registry; Cancer incidence report; 2011 Ardawi MS, et al; High prevalence of vitamin D deficiency among healthy Saudi Arabian men: relationship to bone mineral density, parathyroid hormone, bone turnover markers, and lifestyle factors; Osteoporos Int. 2012 Feb Curado M, et al. Cancer incidence in five continents : IARC scientific publications 2007 Bikle DD; Vitamin D and cancer: the promise not yet fulfilled; Endocrine. 2014 May Roskies M, et al; Vitamin D deficiency as a potentially modifiable risk factor for thyroid cancer