The thyroid gland is considered to be one among the largest endocrine glands in the body. The thyroid is a butterfly shaped gland that lies above the collar bone beneath the neck cartilage. The thyroid gland is located below the thyroid cartilage at the laryngeal prominence (Adam’s apple) in front of the neck. The gland contains two poles, upper and lower; two lobes, right and left; that are joined by the isthmus at the center of the thyroid, which is situated below the cricoid cartilage.The main function of the thyroid gland is to stimulate the rate of metabolism in the body. The parafollicular cells of the thyroid gland secrete a hormone called calcitonin, which combines together with the parathyroid hormone secreted by the parathyroid gland ( located in 2 pairs above the thyroid gland), to regulate the calcium homeostasis in the body.