Relationship between vitamin D and adolescents' hypothyroidism - a cross-sectional study.

Introduction: To detect the relationship between 25(OH)D and hypothyroidism in adolescents.

Material and methods: A total of 180 adolescents were included in the current study, which was conducted in West Kazakhstan (Aktobe) over 2 years. After thorough evaluation, blood samples were collected from the studied participants to measure the thyroid stimulating hormone (TSH), free thyroxine (T4), prolactin, glycosylated haemoglobin, and 25(OH)D. Participants were classified into a 25(OH)D-deficient group (study group) and controls. MedCalc and correlation analysis (Pearson's correlation) were used to detect the odds of hypothyroidism and the relationship between 25(OH)D and adolescents' hypothyroidism, respectively.

Results: Thyroid-stimulating hormone was statistically higher in the 25(OH)D-deficient group than in the normal controls (3.71 ±1.4 mIU/ml vs. 2.67 ±0.99) (p = 0.0006), and the free T4 was statistically lower in the 25(OH)D-deficient group than in normal controls (1.4 ±0.56 ng/ml vs. 1.5 ±0.4) (p = 0.0008). The 25(OH)D deficient group had higher odds of subclinical (OR 4.89; p = 0.016), and clinical hypothyroidism (OR 4.3; p = 0.013) compared to controls. A significant negative correlation between the 25(OH)D and TSH (r = -0.793; p < 0.00001), and a significant positive correlation between the 25(OH)D and free T4 (r 0.55; p < 0.00001) were detected in this study.

Conclusions: The thyroid-stimulating hormone was statistically higher and the free T4 was statistically lower in the 25(OH)D-deficient group than in normal controls. The 25(OH)D-deficient group had higher odds of both subclinical and clinical hypothyroidism compared to controls. A significant negative correlation between the 25(OH)D and TSH, and a significant positive correlation between the 25(OH)D and the free T4 were detected in this study.