Hormonal control of collagen metabolism--Part I.

The collagens are a group of the connective tissue proteins widely distributed in human and animal body. The collagens together with other components of the tissue form a complex regulatory system, and are subject to hormonal control. The present paper reviews the effect of thyroid hormone and thyroid-stimulating hormone (thyrotropin) on collagen. Thyroid hormone influences collagen biosynthesis and degradation, and this effect is responsible for various pathophysiological phenomena, including alterations in urinary excretion of hydroxyproline and hydroxylysine, hyperthyroid acropachy, pretibial myxedema, impaired wound repair and other fibrosis-associated processes as well as a tadpole tail resorption in amphibians. Thyrotropin also directly affects the connective tissue, and is responsible for exophthalmos caused by acumulation of certain components of the tissue in retrobulbar space. Collagen fibres are present in the thyroid gland, and take part in the embryogenesis of the gland.