The thyroid gland is a small, butterfly-shaped endocrine gland located in the base of the neck, just below the Adam’s apple. Its main function is to create thyroid hormones, T4 and T3. T4 and T3 are then released into the blood and are transported throughout the body, where they control metabolism, the conversion of oxygen and calories to energy. Every cell depends upon thyroid hormones for regulation of their metabolism. In fact, every cell in the body has receptors for thyroid hormones and these hormones impact all major systems directly, acting on the brain, the gastrointestinal tract, the cardiovascular system, bone and red blood cell metabolism, gall bladder and liver function, steroid hormone production, glucose, lipids, cholesterol and proteins metabolism, as well as body temperature regulation. It’s a control centre for your entire body.
The thyroid gland is part of a network of communication called the hypothalamic-pituitary-thyroid axis (HPT axis), which also include the hypothalamus and the pituitary gland. The pituitary gland reads and responds to the amounts of T4 circulating in the blood, but it also responds to the hypothalamus, which is a section of the brain that releases the hormone TRH (thyrotropin-releasing hormone). TRH stimulates TSH (thyroid-stimulating hormone) release in the pituitary gland that gets released to promote thyroid hormone production.