The thyroid is an endocrine gland situated at the base of the neck in the front. It is enclosed by fibrous tissue and well supplied with blood, and internally consists of numerous vesicles containing a jelly-like colloidal substance. Under the control of thyroid-stimulating hormone released by the pituitary gland, these vesicles produce the thyroid hormone, which is rich in iodine. Two hormones are produced by the gland, thyroxine and triiodothyronine, which are essential for the regulation of metabolism and growth.

Hyperthyroidism is caused due to excessive activity of the thyroid gland. The symptoms include flushing, sweating and feeling warm, itchy skin, anxiety and over-activity, insomnia, rapid heart beat, breathlessness, weight loss or gain, protrusion of eyes and weariness.