Gene Structure and Regulation

The polypeptide hormones are a diverse group of small proteins, approximately 50 in number, ranging in size from three to 300 amino acids, that regulate the processes of metabolism, reproduction, growth, and development (1). In the broad sense, however, many of these polypeptides can be considered regulatory peptides because they serve not only as hormones in which their actions are mediated on target organs by way of their transport through the bloodstream, but also as local cell-to-cell communicators. The designation of the term hormones to certain of these polypeptides is a consequence of the initial physiologic observations that they are products of specific organs and endocrine glands, and are released into the bloodstream to exert their actions on distant target organs. The products of the actions of the hormones in turn regulate (often inhibit) the further production of the specific hormones.