The thyroid is a small butterfly-shaped gland that sits in front of the trachea or windpipe. It is responsible for producing thyroid hormone (T4 and T3), which is involved in regulation of metabolism, bowel function, heart rate, temperature sense, menstrual regularity, and other functions.
The thyroid is controlled by the pituitary gland in the brain. The pituitary gland produces Thyroid Stimulating Hormone (TSH), which controls the secretion of hormone from the thyroid gland.