Assessing the correlation between vitamin D deficiency and hypothyroidism

Vitamin D deficiency is pervasive globally and has been linked to thyroid dysfunction. This study was a quantitative, observational, case–control study that investigated the relationship between vitamin D deficiency and hypothyroidism in Erbil City, Iraq. We also examined the relationship between biomarkers (thyroxine (T4) and triiodothyronine (T3), thyroid-stimulating hormone (TSH), anti-thyroid peroxidase (TPO) antibodies) of thyroid function and vitamin D deficiency. The study revealed that 36.7% had moderate vitamin D deficiency, 25% had severe deficiency, 18.3% had insufficient levels, and only 20% had sufficient vitamin D levels. Among participants, 95%, 90%, and 82% had normal levels of T3, T4, and TSH, respectively. A remarkable inverse relationship was found between vitamin D levels and hypothyroidism (r = −0.294, p<0.05 for euthyroid participants and r = −0.326, p<0.05 for hypothyroid participants) as well as upward relationship between vitamin D supplementation and hypothyroidism severity (r = −0.859, p<0.01 for euthyroid participants and r = 0.604, p<0.05 for hypothyroid participants), suggesting an indispensable role of vitamin D in thyroid health. Autoimmune markers, such as anti-TPO antibodies and thyroxine dosage, were strongly associated with hypothyroidism severity (P < 0.01). Our findings highlight the significance of personalized dietary vitamin D regimens and supplemental forms in combating thyroid dysfunction on public health scales.