A population of rats treated with a single dose of cortisol on their first day of life and a population of rats underfed since day sixteen of gestation until sacrificed have been studied. Body, brain and liver glycogen content have been measured at eight, twelve and twenty-two days of life and compared to controls of the same age. Pituitary growth hormone and thyrotrophin content have also been measured in the same population of animals and at the same stages of life. Results are compared to those found in "neo-T4" rats -- which receive 30 micrograms T4 in 5 doses during the first days of life -- at the same ages.