Which of the following is associated with hypothyroidism in Himalayan region?

Answer is D (Selenium): Hypothyroidism and Hashimoto's Thyroiditis (2013) Hypothyroidism in Himalayan region is associated with Iodine Deficiency and Selenium deficiency. Selenium is a trace element that plays a role in thyroid hormone production, as it forms pa of a seleno-enzyme responsible for conveing T4 into T3. Selenium deficiency as a causative factor for Hypothyroidism and Goitre formation has been explained by diminished activity of selenocysteine enzymes in thyroid, notably glutathione peroxidase and deiodinase type-1. Type-1 deiodinase enzyme is required for conversion of T4 to T3 in peripheral tissues. Mountainous regions, such as the Himalayas, the Andes, and the Alps, and flooded river valleys, such as the Ganges, are among the most severely iodine-deficient areas in the world. The problem of Iodine deficiency in these areas is fuher compounded by deficiency of Selenium.