Introduction

Figure 28.1 The process of amphibian metamorphosis, as seen in the tadpole-to-frog stages shown here, is driven by hormones. (credit “tadpole”: modification of work by Brian Gratwicke)

Chapter Outline

28.1 Types of Hormones

28.2 How Hormones Work

28.3 Regulation of Body Processes

28.4 Regulation of Hormone Production

28.5 Endocrine Glands

An animal’s endocrine system controls body processes through the production, secretion, and regulation of hormones, which serve as chemical “messengers” functioning in cellular and organ activity and, ultimately, maintaining the body’s homeostasis. The endocrine system plays a role in growth, metabolism, and sexual development. In humans, common endocrine system diseases include thyroid disease and diabetes mellitus. In organisms that undergo metamorphosis, the process is controlled by the endocrine system. The transformation from tadpole to frog, for example, is complex and nuanced to adapt to specific environments and ecological circumstances.

The study of the endocrine system has led to many medical advances. Now scientists have discovered a hormone that mimics the effects of exercise by regulating metabolism and fighting insulin resistance.