Benign nodules of the thyroid gland and 25-hydroxy-vitamin D levels in euthyroid patients

BACKGROUND: The presence of nodules in the thyroid gland is common in iodine-deficient areas of the world. Recently, vitamin D levels were found to be lower than normal and sometimes deficient in malignant nodules of the thyroid. OBJECTIVE: Evaluate the relationship between the serum vitamin D levels and benign thyroid nodules in euthyroid patients. DESIGN: Cross-sectional. SETTING: Tertiary care center in Turkey. PATIENTS AND METHODS: Patients referred to the general surgery outpatient clinic and diagnosed with thyroid nodules were the study group. The control group consisted of healthy individuals without thyroid nodules. Age, BMI, thyroid ultrasonography, serum 25-hydroxyvitamin D, free T3, free T4, thyroid stimulating hormone, calcium, magnesium, phosphorous, total protein, albumin, glucose, creatinine levels and glomerular filtration rate (GFR) were compared between groups. MAIN OUTCOME MEASURE: Serum 25-hydroxy-vitamin D levels and size of the thyroid nodules. SAMPLE SIZE AND CHARACTERISTICS: Of 849 individuals, 453 were patients with thyroid nodules and 396 were healthy individuals. RESULTS: The mean serum vitamin D levels of patients with thyroid nodules were significantly lower than controls (P<.001). Serum vitamin D levels along with serum total protein levels and eGFR were independent variables associated with the presence of a thyroid nodule (P<.001, p=.005 and P=.017, respectively). CONCLUSION: These findings suggest vitamin D deficiency might be one of the pathophysiologic factors in development of thyroid nodules. LIMITATION: Single-center and possible information bias. CONFLICTS OF INTEREST: None.