Gland, organ that manufactures chemical substances. A gland may vary from a single cell to a complex system of tubes that unite and open onto a surface through a duct. The endocrine glands, e....

Parathyroid glands, four small endocrine bodies, located behind the thyroid gland, that govern calcium and phosphorus metabolism. These four masses of tissue (each about the size of a pea) are...

Pituitary gland, small oval endocrine gland that lies at the base of the brain. It is sometimes called the master gland of the body because all the other endocrine glands depend on its secreti...

Endocrine system, body control system composed of a group of glands that maintain a stable internal environment by producing chemical regulatory substances called hormones. The endocrine syste...

Thyroxine, substance secreted by the thyroid gland. The hormone thyroxine forms by combining the amino acid tyrosine with iodine. Complexed to a protein, it is stored in the follicle stems bet...

Thyrotropin or thyroid-stimulating hormone (TSH), hormone released by the anterior pituitary gland that stimulates the thyroid gland to release thyroxine. The release of thyrotropin is trigger...

Neoteny, in biology, sexual maturity reached in the larval stage of some animals. Certain environmental conditions can inhibit the completion of metamorphosis; low temperature or lack of avail...

Kendall, Edward Calvin, 1886–1972, American biochemist, b. South Norwalk, Conn., grad. Columbia (B.S., 1908; Ph.D., 1910). At St. Luke's Hospital, New York City, he did research on the thyroid...

Molting, periodical shedding and renewal of the outer skin, exoskeleton, fur, or feathers of an animal. In most animals the process is triggered by secretions of the thyroid and pituitary glan...

Cretinism, condition produced in infants and children due to lack of thyroid hormone. It usually results from a congenital defect (e.g., absence of the thyroid, presence of only a rudimentary ...