Thyroid Thyroid The thyroid gland, or simply the thyroid, is an endocrine gland in the neck, consisting of two lobes connected by an . It is found at the front of the neck, below the Adam's apple. The thyroid gland secretes thyroid hormones, which primarily influence the metabolic rate and protein synthesis. The hormones also have many other effects including those on development. The thyroid hormones triiodothyronine (T) and thyroxine (T) are created from iodine and tyrosine. The thyroid also produces the hormone calcitonin, which plays a role in calcium homeostasis. Hormonal output from the thyroid is regulated by thyroid-stimulating hormone
Thyroid up to 85% of the T in blood is produced following conversion from T by iodothyronine deiodinases in organs around the body. Thyroid hormones act by crossing the cell membrane and binding to intracellular nuclear thyroid hormone receptors TR-α,TR-α,TR-β and TR-β, which bind with hormone response elements and transcription factors to modulate DNA transcription. In addition to these actions on DNA, the thyroid hormones also act within the cell membrane or within cytoplasm via reactions with enzymes, including calcium ATPase, adenylyl cyclase, and glucose transporters. The thyroid hormones are created from thyroglobulin. This is a protein within the follicular space