Which of the following is necessary for the thyroid gland to make thyroxin hormone ? 

Iodine 

The correct answer is Option (2) – Iodine

Iodine is necessary for the thyroid gland to make thyroxin hormone. Thyroxin regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth. Iodine is essential for the synthesis of thyroxin.

In case iodine is deficient in our diet, there is a possibility that we might suffer from goitre.

One of the symptoms in this disease is a swollen neck.