thyroid gland
17.4 The Thyroid Gland The thyroid gland is a butterfly-shaped organ located in the neck anterior to the trachea. Its hormones regulate basal metabolism, oxygen use, nutrient metabolism, the production of ATP, and calcium homeostasis. They also contribute to protein synthesis and the normal growth and development of body tissues, including maturation of the nervous system, and they increase the bodys sensitivity to catecholamines. The thyroid hormones triiodothyronine T3 and thyroxine T4 are produced and secreted by the thyroid gland in response to thyroid-stimulating hormone TSH from the anterior pituitary. Synthesis of the amino acidderived T3 and T4 hormones requires iodine. Insufficient amounts of iodine in the diet can lead to goiter, cretinism, and many other disorders.