DefinePK

Abstract

Background: Subclinical hypothyroidism defines elevated serum thyroid stimulating hormone with normal thyroxine in the circulation. While often symptomless, subclinical hypothyroidism can evolve towards overt disease and cause metabolic as well as cardiovascular complications. Deficiency in vitamin D is extremely common and has been implicated in defective thyroid physiology by virtue of its immunomodulatory action. It has been posited that supplementation might correct thyroidal as well as metabolic outcomes in individuals so affected. Objective: To evaluate the effect of vitamin D replacement on thyroid stimulating hormone levels in patients with subclinical hypothyroidism. Study Design: It was Quasi-experimental study. Study Duration and Setting: Conducted from June 2025 to August 2025 at PAF Hospital, Islamabad. Methodology: A total of 60 patients aged 18–60 years with subclinical hypothyroidism were included. Participants received oral vitamin D supplementation of 50,000 IU weekly for eight weeks. Serum thyroid stimulating hormone, thyroxine, and vitamin D levels were measured before and after intervention. Results: The mean age of participants was 38.5 ± 12.7 years, with female predominance (78.3%). Vitamin D supplementation significantly reduced mean thyroid stimulating hormone levels from 7.05 ± 1.25 to 3.44 ± 1.38 mIU/L (p < 0.001). Serum Vit D increased from 16.07 ± 5.02 to 37.08 ± 7.22 ng/mL (p < 0.001). Conclusion: Vitamin D replacement therapy effectively improves thyroid function in patients with subclinical hypothyroidism.