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.