The functions attributed to fetal glucocoicoids are: Induce development and maturation of various enzyme systems in the liver Aid in maturation of pancreatic b cells Play a role in change from HbF to HbA Stimulate synthesis of surfactant by type II pneumocytes Play a role in paurition Stimulate formation of adrenal medulla and synthesis of catecholamines Thymus increases in size up to 5th year of life. Involution of thymus occurs at the time of pubey. Although it is brought about by glucocoicoids, involution of thymus is not a function of fetal/maternal glucocoicoids, as it continues to grow in size until much after bih. Before second trimester, most of the T4 in fetus is maternal. Fetal production of thyrotropin (TSH) and the T4 begin to increase in the second trimester, concurrent with development of the hypothalamic-pituitary poal system. Maternal glucocoicoids may have a role in the functional hypothalamo-pituitary axis in fetus.