The endocrine system is made up of the pituitary gland, the thyroid gland, the pancreas, and the ovaries/testes. These organs secrete a variety of hormones including growth hormone, insulin, thyroid hormone, estrogen, testosterone, etc. The hormones produced in the endocrine system regulate a variety of functions in the body, including metabolism, growth, reproduction, and development.
Three hormones T3 (Triiodothyronine), T4 (Thyroxine), and Calcitonin are produced by the thyroid gland. T3 and T4 are used by the body to regulate energy and metabolism. As these hormones enter the bloodstream, they are transported throughout the body and are found in almost every type of cell in the body.