Answer: Iodine-131 radioisotope is used to detect thyroid malfunction.
Explanation: Iodine-131 is a radioisotope of iodine.
It emits radiations and thus are helpful in medical purposes. It is used for various medical purposes, but one of them is to detect thyroid malfunction happening in the body.
The therapy used for thyroid treatment is called as Radio-iodine therapy. A small dose of Iodine -131 is swallowed which is absorbed in the blood stream and then it is concentrated by the thyroid gland where it begins to destroy the gland's cell.