The correct option is D Thyroxine
The thyroid gland is an endocrine gland situated in the anterior (front) portion of the neck. It secretes a hormone known as thyroxine which regulates the carbohydrate, protein and fat metabolism in our body.
Iodine is essential for the thyroid gland to synthesise thyroxine. Lack of iodine would result in enlargement of thyroid gland called goitre.