Thyroid is an endocrine gland located under the voice box (larynx) at the front of the neck. The lobes at opposite sides of the gland give it a butterfly shape. They lie around the windpipe (trachea) and converge by a thin bridge of tissue in the middle named the isthmus. 

 

The gland weighs 20-60 g and is surrounded by two fibrous capsules(inner and outer). The outer capsule is connected to the larynx and many other important nerves and muscles. The loose connective tissue between the two capsules allows for the movement of the gland so we can swallow easily.

 

Thyroid is an essential gland since it is vital in the processes of growth, development and metabolism in the body. It controls these processes by secreting a multitude of hormones called the thyroid hormones. The thyroid tissue contains multiple singular lobes enclosed in layers of connective tissue; these contain follicles which store droplets of thyroid hormones.

The gland regulates various bodily functions by ensuring that a stable amount of thyroid hormones are constantly circulating in the blood. 

 

The gland secretes three hormones: Triiodothyronine (T3), Tetraiodothyronine (thyroxine or T4) and Calcitonin. Only T3 and T4 are synthesized in the follicle cells. T3 and T4 are responsible for increasing the body’s basal metabolic rate. Calcitonin is made by the C-cells in the thyroid gland and plays a role in calcium and bone metabolism.