Endocrine regulation of fetal metabolism towards term

Hormones have an important role in regulating fetal metabolism in relation to the prevailing nutritional conditions both in late gestation and during the prepartum period as the fetus prepares for birth. In particular, the pancreatic, thyroid and adrenal hormones all affect fetal uptake and utilization of nutrients for oxidative metabolism, tissue accretion and fuel storage. These hormones also influence the fetal metabolic preparations for the nutritional transition from intra- to extra-uterine life. This review discusses the role of insulin, glucagon, thyroxine, tri-iodothyronine, cortisol and the catecholamines in these processes during normal intrauterine conditions and in response to maternal undernutrition with particular emphasis on the sheep fetus. It also considers the metabolic interactions between these hormones and their role in the maturation of key tissues, such as the liver, skeletal muscle and adipose tissue, in readiness for their new metabolic functions after birth. Endocrine regulation of fetal metabolism is shown to be multifactorial and dynamic with a central role in optimizing metabolic fitness for survival both in utero and at birth.