Chapter 16: Endocrine and Neuroendocrine Physiology

Endocrine and Neuroendocrine Physiology explains how energy acquisition and allocation are central to survival and life history strategies. The text delves into the biochemistry of nutrition, outlining the roles of carbohydrates, proteins, lipids, vitamins, and minerals in meeting metabolic demands. Particular attention is paid to essential amino acids and fatty acids—nutrients that must be obtained from the diet—as well as micronutrients that support enzyme function and physiological balance. The authors examine the principles of growth by distinguishing between determinate and indeterminate growth, and by describing how energy availability influences growth rates. Examples include fast-growing fish under high-food conditions and the growth suppression observed during caloric restriction or environmental stress. Hormonal regulators such as growth hormone, insulin-like growth factors (IGFs), and thyroid hormones are discussed in the context of anabolic signaling and developmental transitions. The chapter also addresses developmental physiology, with a focus on how nutrient intake during early life stages—especially in mammals—can program metabolic performance later in life. Case studies include the metabolic plasticity of juvenile fish, early weaning in mammals, and the long-term effects of undernutrition in human infants. The authors introduce the concept of metabolic programming and describe how early-life nutrition can shape later health outcomes via epigenetic mechanisms. Insects and amphibians are presented as models of metamorphosis, where energy stores are tightly regulated to support dramatic physiological remodeling. Finally, the chapter explores ecological aspects of nutrition, including optimal foraging theory and how animals balance macronutrient intake to meet both immediate and long-term needs. Examples such as hummingbird nectar feeding, carnivore protein prioritization, and seasonal fattening in birds show how energy metabolism is tailored to environmental availability and reproductive timing. Altogether, this chapter connects molecular nutrition to physiological development and ecological strategy.