Chapter 9 - The endocrine system: Metabolic effects of the pancreatic, adrenal, thyroidal, and growth hormones

Abstract

This chapter reviews a historical perspective of the role that endocrine glands play in modulating the metabolic responses to acute and chronic exercise. Its scope is limited to the metabolic effects of hormones released by the pancreas (insulin and glucagon), adrenal glands (catecholamines and glucocorticoids), anterior pituitary (growth hormone), and thyroid (thyroxine and triiodothyronine) that play a critical role in regulating substrate mobilization and utilization during muscular work. It also provides a brief history of some of the important studies conducted on exercise and diabetes. The first connections between the endocrine functions and muscular activity were made in the nineteenth century by physiologists who observed that individuals with endocrine disorders have a decreased capacity for physical work. Later, in the late 1960s and beyond, there were systematic investigations of the effects of exercise and physical training on hormones and metabolism. This chapter reflects methodological advances over the last 30 years in the study of endocrinology and metabolism. Since the 1990s, use of nuclear magnetic resonance spectroscopy (NMRS) has made it possible to obtain noninvasive, real-time measurements of intracellular pH, substrate fluxes, and energy metabolism in both liver and muscle tissues in humans. Investigators in the field of endocrinology and exercise have contributed considerably to the understanding of complicated hormone signaling pathways and have provided new insights into how tissues sense and respond to various energy needs.