NEUROENDOCRINE REGULATION OF GROWTH-HORMONE SECRETION

Growth hormone (GH) secretion is controlled by many factors, including stage of development, age, gonadal steroids, body composition, nutrit ional state, time of day and whether the subject is asleep or awake. U nderstanding regulation of GH secretion is important since this hormon e regulates not only growth, but also the partitioning of nutrients an d body composition. There is increasing evidence that there is a basic ultradian rhythm of GH secretion. The NSF Center studies will be faci litated by 3 major efforts: (a) improvement of sensitivity of GH assay s to permit accurate description of GH pulses; (b) use of biomathemati cal models to objectively determine GH pulse characteristics, as well as calculation of secretion rates to facilitate the study of the relat ionship between neural controls and GH secretion; and (c) use of the t au mutant hamster and the new mouse mutant animal models. By manipulat ion of the endogenous circadian clock in these animal models it will b e possible to study the relationship between endogenous circadian syst ems and ultradian GH rhythms.