Although physiological and anatomical evidence had clearly indicated for many years that the secretion of anterior pituitary hormones is under control by the central nervous system, it is only recently that the isolation and determination of structure of three hypo- thalamic hypophysiotropic hormones have been accomplished. This has brought the concept of neurohormonal control of adenohypophyseal function into precise biochemical and chemical terms. The relative ease of synthesis of TRH (thyrotropin-releasing hormone), LH-RH (luteinizing hormone-releasing hormone), somatostatin and their...