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The effect of hormones on developmental events is not a new area of scientific investigation. However, in the last decade, the developing lung has been the focus of an increasing amount of basic and applied research. Inadequate development of the newborn's respiratory system precludes extra-uterine existence; indeed, such respiratory inadequacy has been a leading cause of death in premature infants. Tremendous strides have been made in understanding the basic cell biology of the developing lung. Much has been learned about the source, composition, and function of pulmonary surfactant, a surface-active material produced by the lung and essential to alveolar stability. Deficient stores of this material is a major etiologic factor in the respiratory distress syndrome of the newborn (RDS). This fact, coupled with observations that certain hormones can accelerate lung development and the consequent availability of adequate stores of pulmonary surfactant, has led to a large body of literaturae dealing with the effects of hormones (and other agents) on lung development. It is the purpose of this literature review (1) to discuss the various kinds of investigations which have linked surfactant synthesis to the type II pulmonary epithelial cell; and (2) to review the current status of research dealing with the effects of glucocorticoids and thyroid hormones on lung maturation.

Adult rats were injected intravenously with [125I]-3,5,3'-triiodothyronine (T3) of [125I]-thyroxine (T4). Others were similarly treated, except for the addition of a 500-fold excess of the appropriate unlabeled hormone. Light microscopic autoradiography of semi-thin sections of liver from these animals demonstrated high affinity, low capacity binding of T3 and, to a much lesser extent, T4 to the nuclei of the liver cells. Labeling over the cytoplasmic portion of the cells was greater than that over the nucleus with either hormone, but was not decreased significantly with the addition of unlabelled hormone, suggesting the absence of specific binding sites in this location.