CHAPTER 17: THE ENDOCRINE SYSTEM
Chapter Overview
Introduction
The endocrine system is similar to the nervous system and the senses because they are all concerned with
how the body communicates and coordinates within itself, but how the endocrine system does it’s
communication is very different. The endocrine system uses chemicals called hormones that are carried by
the blood to cause changes in the activities of other cells. Saladin begins with presentations of the
differences between endocrine and exocrine glands and between the endocrine and nervous systems. He
then moves to describing the endocrine glands and tissues, including the anatomy, the secretions, how they
are controlled, and some conditions of imbalance. The glands presented are the hypothalamus, the anterior
pituitary gland, the posterior pituitary gland, pineal gland, thymus, thyroid gland, parathyroid glands,
adrenal glands, pancreatic islets, and the gonads. Saladin then explains the endocrine functions of other
tissues and organs. He then spends time explaining hormones and their actions. This includes hormone
chemistry, synthesis, secretion, transport, receptors, signal amplification, modulation of target-cell
sensitivity, interactions of hormones, and hormone clearance from the body. Stress is then presented with
its physiological effects on the endocrine and sympathetic nervous systems. Eicosanoids and other
signaling molecules are described. Saladin then explains general causes and examples of hyposecretion and
hypersecretion of hormones, particularly of the pituitary, thyroid, parathyroid, adrenal glands, and the
pancreatic islets.
Key Concepts
Here are some concepts that students should have a better understanding of after reading this chapter:
 the distinctions between the nervous and endocrine systems;
 the roles of the hypothalamus and adenohypophysis and the control of pituitary secretions;
 the functions of the posterior lobe of the pituitary;
 the importance of and mechanisms of feedback in the control of hormone production;
 the main endocrine organs with their hormones, actions, and control - hypothalamus, the anterior
pituitary gland, the posterior pituitary gland, pineal gland, thymus, thyroid gland, parathyroid
glands, adrenal glands, pancreatic islets, and the gonads.
 the chemical nature of various hormones plus their synthesis, transport, clearance, and
interactions;
 hormone receptors, second messengers, enzyme amplification, and other changes coming about
within the target cell;
 effects of hormone concentration and changes in numbers of receptor sites;
 the symptoms of diabetes mellitus and the distinctions in causes and treatments between the
insulin dependent and non-insulin dependent forms;
 hormones coming from organs not primarily endocrine in function;
 the importance of hormone deactivation;
 eicosanoids and their relation to anti-inflammatory drugs;
 the stress reaction;
 the development and diagnosis of significant endocrine disorders such as hypopituitarism,
hyperpituitarism, diabetes insipidus, hypothyroidism, endemic goiter, Graves disease,
hyperparathyroidism, pheochromocytoma, Cushing syndrome, SAD, and others;
 and the history of insulin research.
Topics for Discussion
1.
Because of the marketing of growth hormone (i.e., GH) produced by genetically engineered bacteria, it
is now possible to prevent dwarfism due to hypopituitarism. Some adults with hypopituitary dwarfism
are upset with this development and have gone so far as to call it genocide. What does your class think
of this issue?
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2.
3.
Students may be interested in discussing the use of GH in dairy cattle.
It is now possible to buy genetically engineered human GH and EPO by mail order or over the Internet
for personal use. Your students may know somebody who is using these compounds. Encourage them
to discuss the dangers.
4. Is it fair for athletes to use steroids, GH, and EPO while others in the same sport may not be able to
afford these things?
5. Steroid rage occurs sometimes in body builders. Ask your students if they know of cases of this
happening.
6. Insulin resistance, sometimes called metabolic syndrome, which can lead to diabetes mellitus type 2, is
a hot topic these days with as much as 30% of the US population carrying one of the genes for it. Some
students may be interested in further research in this area. An internal medicine specialist should be
able to provide individual information on risk factors.
7. Explain the medical workup for hyperthyroidism; explain the rationale for drawing a blood T3 and T4
level along with a TSH level and FTI (free thyroid index).
8. Explain, in detail, the multistep process for thyroid hormone formation; explain how propylthiouracil
and methimazole can be used to treat hyperthyroidism.
9. Discuss the various GLUT receptors.
10. Explain and discuss MODY (maturity onset diabetes in the young).
11. Explain the actions of some of the various drugs for diabetes mellitus.
12. Discuss the various types of glucose tolerance tests; graphically show how the normal glucose
tolerance test results should chart out over time. Show a chart of the role of each anatomic structure
associated with skeletal muscle contraction.
Related Readings
Braverman, L.E. and R.D. Utiger. Werner and Ingbars’ The Thyroid: A Fundamental and Clinical Text,
10th ed. Baltimore, MD: Lippincott Williams & Wilkins, 2012. The classic text.
Camacho, P.M. et al. Evidence-Based Endocrinology, 4th ed. Philadelphia, PA: Wolters Kluwer, 2020.
Fulzele, K, et al. “Insulin Receptor Signaling in Osteoblasts Regulates Postnatal Bone Acquisition and
Body Composition,” Cell 142 (2010): 309-319. Osteoblasts release osteocalcin, which regulates
insulin secretion.
Gerstein, H.C. et al. “Effects of Intensive Glucose Lowering in Type 2 Diabetes,” New England J. Med.
358 (2008): 2545-2559. There is fear that there is an impending epidemic of DM 2 in the U.S.
Giovannucci, E. and M. Pollack. “Risk of Cancer After Growth-Hormone Treatment,” Lancet 360 (2002):
268-269.
Greene, M.F. and C.G. Solomon. “Gestational Diabetes Mellitus—Time to Treat,” N. Engl. J. Med. 352
(2005): 2373-2375.
Hishinuma A., et al. “Insulin Resistance in Patients with Stroke is Related to Visceral Fat, Obesity, and
Adipocytokines,” J. Stroke. Cerebrovasc. Dis. 17 (2008):175-180.
Hoerger, T.J. and A.J. Ahmann. “The Impact of Diabetes and Associated Cardiometabolic Risk Factors on
Members: Strategies for Optimizing Outcomes,” J. Manag. Care Pharm 14, Supplement C (2008): S2S14.
Ismali-Beigi, F. et al. “Effect of Intensive Treatment of Hyperglycaemia on Microvascular Outcomes in
Type 2 Diabetes: An Analysis of the ACCORD Randomised Trial,” The Lancet 376 (2010): 419-430.
Intensive control is not always best.
Lovas, K. and E.S. Husebye. “Addison’s Disease,” The Lancet 365 (2005): 2058-2061. There are some
good illustrations here.
Melmed, S. et al. Williams Textbook of Endocrinology, 14th ed. New York, NY: Elsevier, 2020.
Pandi-Perumal S.R. et al. “Melatonin and Sleep in Aging Population,” Exp. Gerontol. 40 (2005): 911-925.
Strong, R.E., et al. “Narrow-Band Blue-Light Treatment for Seasonal Affective Disorder in Adults and
Additional Non-Seasonal Symptoms,” Depress. Anxiety 26 (2009): 273-278. Around 470 nm seems to
be the effective wavelength.
Taguchi, T. and Y. Terada. “Subperiosteal Bone Resorption,” New Engl. J. Med. 370 (2014): e32.
Wright, K. “Times of Our Lives,” Sci. Am. 287 (2002): 59-65. She discusses the rolls of the superchiasmic
nucleus, pineal gland, ganglia cells in the retina, and circadian clocks in many tissues.
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Learning Strategies and Techniques
1.
Students often confuse the activities of the nervous system with those of the endocrine system.
Saladin’s Table 17.1 and Fig. 17.2 is a very good way to try to clarify this issue. There is quite a bit of
overlap: some hormones, such as CCK and norepinephrine, are also neurotransmitters or
neuromodulators. Certain organs play prominent roles in both systems, the most obvious in this
category being the hypothalamus.
2. Many curricula and course objectives require that students be able to know most, if not all the
hormones and glands in this chapter. This may make your students’ task of studying the endocrine
system a little easier: Hormones with either “releasing” or “inhibiting” in their names have the
hypothalamus as their source.
3. Here’s an analogy: if hormones are the letters and the endocrine glands are the senders, then the target
cells are the recipients of the letters. Some endocrine disorders are due to a failure to mail the letter;
some are due to a failure of the recipient to have a mailbox (lack of hormone receptor).
4. Provide models showing the endocrine glands and their placement.
5. Sheep brains with intact meninges are useful to illustrate the hypothalamus and pituitary gland. A
sagittal section will illustrate the pineal body. Compare the pineal body of a sheep with that of a
human. The sheep pineal is larger in proportion to brain size than that of a human possibly because
melatonin in other mammals is so important in setting female reproductive cycles.
6. The HPA/HPO axis is often a difficult concept to illustrate simply. Use a tablet or document camera to
project a blank diagram on the screen and have the students talk you through the negative feedback
regulation of important hormones (ACTH and TSH are good ones to start with). Drawing the negative
feedback loops along with the class makes the process (and all of the arrows) easier to follow.
7. Show a glucometer and demonstrate how it is used to obtain blood glucose levels.
8. Explain and discuss the dexamethasone suppression test.
9. Show a movie of a transsphenoidal hypophysectomy.
10. Show pictures of patients with dwarfism, gigantism, and acromegaly.
11. In chart form, explain the onset and duration of the various types of insulins.
12. Discuss the thyroglossal duct cyst.
13. Explain and discuss ectopic gland secretions such as that in the small cell carcinoma of the lung
producing ACTH.
14. Explain and discuss the deleterious actions of endocrine disruptors.
15. Using a SMART Board, show how gonadotropins, follicle-stimulating hormone (FSH), and luteinizing
hormone (LH) regulate gamete production.
16. Using a SMART Board, show how adrenocorticotropic hormone (ACTH) regulates the endocrine
activity of the cortex of the adrenal gland.
17. Demonstrate how to palpate the thyroid gland.
18. Demonstrate how to examine the microscopic structure of the thyroid gland.
Related Multimedia
Anatomy and Physiology Live-Action Video Series; Denoyer-Geppert
Endocrine Glands. Medlineplus.gov
Endocrine Signs and Symptoms; Insight Media
Endocrine System. Guidance Associates.
Endocrine System: Molecular Messengers, Chemical Control. DVD, Carolina.
Endocrine System: Molecular Messengers. DVD, Carolina.
Hormones: Messengers; Films for the Humanities and Sciences
Human Body in Action. DVDs, Schlessinger Science Library.
Human Body Systems: The Endocrine System. DVD, United Learning.
Human Body: Reproductive & Endocrine Systems. DVD, Carolina.
Reproductive & Endocrine Systems. DVD, Library Video Company.
Steroid, Thyroid Hormones, and the Endocrine System. Great Pacific Media.
Teens and Hormones: Understanding the Endocrine System. DVD, Educational Video Network.
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The Endocrine System DVD Series: The Human Body: How It Works. Films for the Humanities and
Sciences
The Endocrine System. Viewtech Educational Media.
The Endocrine System: Molecular Messengers, Chemical Control; Insight Media
The Endocrine System: Regulating the Body's Chemistry. DVD, Rainbow.
The Endocrine System; Insight Media, Films for the Humanities and Sciences
YouTube.com videos and animations
The Endocrine System
Endocrine System: Glands and Hormones
Human Endocrine System Made Simple
Great Glands: Your Endocrine System
Related Software
Anatomy and Physiology Revealed; available through Connect from McGraw Hill
Module 8 – Endocrine System
Hypothalamus and pituitary glands
Suprarenal (adrenal) glands
Thyroid gland
Parathyroid glands
Pancreas
Hormonal communication
Receptors and G proteins
Intracellular receptor model
2+
Second Messengers: The cAMP & Ca pathways
Endocrine system overview (Interactive)
Hormone Action (Interactive)
Target Cell Response (Interactive)
Thyroid function/Hyperthyroidism (Clinical application)
Type 1 Diabetes (Clinical application)
Type 2 diabetes (Clinical application)
Endocrine, Reproductive, and Lymphatic Systems; Insight Media
Ph.I.L.S.; available through Connect from McGraw Hill
Thyroid Gland and Metabolic Rate
Insulin and Glucose Tolerance
Anti-diuretic Hormone
Glucose Transport
Animations Found with the Presentation Tools available from Connect from McGraw Hill
Action of Glucocorticoid Hormone
Blood Sugar Regulation in Diabetics
Blood Sugar Regulation
Calcium Levels in the Blood
Glucocorticoid Hormone
Homeostasis of Blood Glucose
Homeostasis Hypoglycemic Condition
Hormonal Communication
Hormones and Gastric Secretion
Mechanism of Steroid Hormone Action
Mechanism of Thyroxine Action
Hypothalamus and pituitary glands
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Suprarenal (adrenal) glands
Thyroid gland
Parathyroid glands
Pancreas
Hormonal communication
Receptors and G proteins
Intracellular receptor model
Second Messengers: The cAMP & Ca2+ pathways
Endocrine system overview (Interactive)
Hormone Action (Interactive)
Target Cell Response (Interactive)
Thyroid function/Hyperthyroidism (Clinical application)
Type 1 Diabetes (Clinical application)
Type 2 diabetes (Clinical application)
Virtual Labs; available from Connect from McGraw Hill
Endocrine System
Critical Thinking Questions
1.
2.
3.
4.
5.
A tumor of the paraventricular nucleus of the hypothalamus might manifest itself by an excess of
which hormone?
Using the information in chapter 17, why would growth hormone be a useful way to increase milk
production in dairy cows?
A man and a woman have been trying to have a baby because their relatives are making life very
unpleasant for them due to the childlessness of the couple. Can you explain one cause of the problem?
A very slender young man is found wandering and disoriented on a street. His speech is slurred, and he
smells as if he has drunk too much of the local hard apple cider. Your friend, the organic chemist, says
that apple cider smell is actually the smell of ketones. As the young man seems to have urinary
incontinence, a police officer wants to just get him into the drunk tank as quickly as possible. What
life-saving suggestion should you have?
If you wished to control chronic high blood pressure in a person, which hormones should you block?
Assume that this individual exhibits no signs of emotional stress.
Critical Thinking Answers
1.
2.
3.
4.
5.
Oxytocin is produced by the paraventricular nucleus of the hypothalamus and so may occur in excess
with a tumor at that site (Fig. 17.4).
Growth hormone increases cell differentiation and mitosis so that would seem to increase mammary
cell proliferation. Protein synthesis is increased and calcium ion transport is improved.
Persons under stress produce an excess of cortisol. The cortisol will suppress the production of sex
hormones. The prospective grandparents should chill out a little if they want to hear those little feet!
Test him for diabetes mellitus. The symptoms more specifically match Type I diabetes mellitus and the
man may have lost his insulin which he may need soon to avoid coma and even death.
Blocking angiotensin II and aldosterone would be effective (Section 17.3e; Table 17.5). ACE
inhibitors are commonly used to help heart patients but, fairly recently, it has been found that
controlling aldosterone is also useful. Thyroid hormone levels might also be checked since these can
increase heart rate too.
Clinical Application Question
Samantha has a pulse rate greater than 100 beats/min and her eyes seem to be unusually prominent. She is
also underweight and hyperactive. What type of operation most likely would be contemplated? What
medication will she most likely require for the rest of her life?
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Clinical Application Answer
Samantha seems to have toxic goiter or Graves disease (Table 17.8). A thyroidectomy is the preferred
operation in this condition. However, Samantha may undergo a course of radioactive iodine. The thyroid
uses iodine to produce T4 (Fig. 17.17) so the radioactivity will destroy the thyroid. Without a thyroid, she
will clearly need to take thyroid hormone replacement for the remainder of her life.
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