Introduction to the Endocrine System

Learning Objectives

After studying this chapter, you will be able to:

  • Identify the major classes of hormones on the basis of chemical structure
  • Distinguish the types of intercellular communication, their importance, mechanisms, and effects
  • Identify the major organs and tissues of the endocrine system and their location in the body
  • Summarize the site of production, regulation, and effects of the hormones of the pituitary, thyroid, parathyroid, adrenal, and pineal glands
  • Explain the interrelationships of the anatomy and functions of the hypothalamus and the posterior and anterior lobes of the pituitary gland
  • Identify the two hormones released from the posterior pituitary, their target cells, and their principal actions
  • Identify the six hormones produced by the anterior lobe of the pituitary gland, their target cells, their principal actions, and their regulation by the hypothalamus
  • Describe the location and anatomy of the thyroid gland
  • Explain the role of thyroid hormones in the regulation of basal metabolism
  • Identify the hormones produced by the follicular and by the parafollicular (C) cells of the thyroid
  • Describe the location and structure of the parathyroid glands
  • Describe the hormonal control of blood calcium levels
  • Discuss the physiological response of parathyroid dysfunction
  • Describe the location and structure of the adrenal glands
  • Identify the hormones produced by the adrenal cortex and adrenal medulla, and summarize their target cells and effects
  • Describe the location and structure of the pineal gland
  • Discuss the function of melatonin
  • Discuss the hormonal regulation of the reproductive system
  • Identify the most important hormones produced by the testes and ovaries
  • Name the hormones produced by the placenta and state their functions
  • Explain the role of the pancreatic endocrine cells in the regulation of blood glucose
  • Identify the hormones released by the heart, kidneys, and other organs with secondary endocrine functions
  • Describe the location and structure of the pancreas, and the morphology and function of the pancreatic islets
  • Compare and contrast the functions of insulin and glucagon
  • Discuss several common diseases associated with endocrine system dysfunction
  • Discuss the embryonic development of, and the effects of aging on, the endocrine system
This photo shows a young girl reaching for an orange leaf on an oak tree. She is on a walkway near a creek. The opposite shore is a deep slope covered with more trees in autumn colors.

A Child Catches a Falling Leaf.

You may never have thought of it this way, but when you send a text message to two friends to meet you at the dining hall at six, you’re sending digital signals that (you hope) will affect their behavior—even though they are some distance away. Similarly, certain cells send chemical signals to other cells in the body that influence their behavior. This long-distance intercellular communication, coordination, and control is critical for homeostasis, and it is the fundamental function of the endocrine system.

Hormones of the endocrine system coordinate and control growth, metabolism, temperature regulation, the stress response, reproduction, and many other functions.