The overall objective of the project remains the study of the late consequences of various metabolic and pathogenic perinatal treatments during a critical neonatal period. Particular attention will be directed to hypothalamo-pituitary, thyroidal and gonadal function of such rats after they are mature. In addition their untreated offspring will be studied. Changes will be noted in goiter growth on propylthiouracil challenge, thyrotropin releasing hormone response, thyrotropin clearance, and fertility.