the endocrine system: the body’s other control system

CHAPTER

ESSENTIALS OF A&PFOR EMERGENCY CARE

Copyright ©2011 by Pearson Education, Inc.All rights reserved.

Essentials of A&P for Emergency CareBruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe

The Endocrine System: The Body’s Other Control System

12



Multimedia Asset Directory

Slide 66 Hyperglycemia AnimationSlide 67 Hypoglycemia AnimationSlide 71 Pathology of Diabetes VideoSlide 72 Insulin VideoSlide 73 Hypothalmic Pituitary Axis AnimationSlide 74 Monitoring Glucose Levels VideoSlide 97 Aging and the Endocrine System VideoSlide 98 Phlebotomy VideoSlide 99 Dieticians Video



Introduction

• The nervous system and the endocrine system are totally interconnected and always monitor each other’s activities.

• The endocrine system also collects information and sends orders but it is a slower, more subtle control system. While it acts slowly, the effects last longer than those of the nervous system.



Learning Objectives

• Discuss the functions of the various endocrine glands.

• Explain mechanisms of control of hormone levels.

• Describe the purpose and effects of hormones within the body.

• Discuss the functions of the various endocrine glands.

• Differentiate between hormonal and humoral control.



Pronunciation GuideClick on the megaphone icon before each item to hear the pronunciation.

adrenal cortex (ad REE nal KOR teks)adrenal medulla (ad REE nal meh DULL lah)endocrine (EHN doh krin)epinephrine (EP ih NEFF rin)homeostasis (HOH mee oh STAY sis)hypothalamus (HIGH poh THAL ah mus)norepinephrine (nor EP ih NEFF rin)oxytocin (AHK see TOH sin)parathyroid gland (PAIR ah THIGH royd)



Pronunciation GuideClick on the megaphone icon before each item to hear the pronunciation.

pineal gland (PIN ee al)pituitary (pih TOO ih TAIR ee)prolactin (proh LAK tin)testes (TESS teez)thymus (THIGH mus)



The Endocrine Organs

• The endocrine system is a series of organs and glands in your body that secrete chemical messengers into your blood stream.

• Exocrine glands, like sweat glands, secrete out of the body, but are not part of the endocrine system that secrete into the body.

• Many glands, like the hypothalamus and pancreas, have multiple functions.



Figure 12-1 The endocrine glands and their hormones.



Table 12-1 Endocrine Organ Functions.



Table 12-1 (continued) Endocrine Organ Functions.



Hormones

• The chemical messengers released by endocrine glands are called hormones.

• Hormones are released into the blood stream and travel all over your body, some affecting millions of cells simultaneously. Their effects last for minutes or even hours or possibly days.

• Many hormones are secreted all the time, with the amount secreted changing as needed.



Table 12-2 Comparison of Neurotransmitters and Hormones.



How Hormones Work

• Hormones work by binding to receptors on target cells. They bind to not only sites outside the cell, like neurotransmitters, but also to sites inside the cell.

• If hormones bind to the outside of the cell, they can have several different effects, either changing cellular permeability or sending the target cell a message that changes enzyme activity inside the cell.



Steroids

• One special class of hormones, called steroids, is particularly powerful because steroids can bind to sites inside cells.

• Steroids are lipid molecules which can pass easily through the target cell membrane, allowing them to interact directly with the cell’s DNA to change cell activity.



Steroids

• They are carefully regulated because only small amounts are needed to perform their task.



Control of Endocrine Activity

• The amount of hormone secreted changes based on situational demands.

• Many endocrine organs secrete hormones continuously.



Homeostasis and Negative Feedback

• Many of the chemical and physical characteristics of your body have a standard level, or set point, that is the ideal level for that particular value. Blood pressure, blood oxygen, heart rate, and blood sugar are examples.

• Your control systems (endocrine and nervous system) work to keep levels at or near ideal.




• There is a way for your body to measure the variable, a place where the ideal level is stored, and a way for your body to fix levels that are not near ideal. For example, the hypothalamus stores the ideal set-point for temperature.



Figure 12-2 Homeostasis is analogous to regulation of temperature via a thermostat.




• If any of your body’s dozens of characteristics become seriously abnormal, your control systems work to bring them back to set point via a process called negative feedback.

• Negative feedback counteracts a change. Thus, as blood pressure rises, your body works to bring it down to normal, the set point. If blood pressure falls, your body works to raise it back up to normal.




• Hormones work the same way. If hormone levels rise, negative feedback will turn off the endocrine organ that is secreting the hormone.



Figure 12-3 Homeostasis and negative feedback as related to control of body temperature.



Positive Feedback

• Positive feedback increases the magnitude of a change.

• The flow of sodium into a neuron during depolarization is a real-life example we have already visited. The more depolarized a neuron becomes, the more sodium flows in, so it becomes more depolarized, so more flows in, etc. This kind of process is also known as a vicious cycle. Positive feedback is not a way to regulate the body, since positive feedback increases a change away from set point.



Clinical Application: Childbirth and Positive Feedback

• Positive feedback is harmful if the vicious cycle cannot be broken, but is sometimes necessary for a process to run to completion. A good example is the continued contraction of the uterus during childbirth. When a baby is ready to be born, a signal tells the hypothalamus to release oxytocin from the posterior pituitary, increasing the intensity of contractions.



Clinical Application: Childbirth and Positive Feedback

• As the uterus contracts, the pressure inside the uterus increases the signal to the hypothalamus and more oxytocin is released, causing the uterus to contract harder. This cycle of ever-increasing uterine contractions, due to ever-increasing release of oxytocin from the hypothalamus, continues until the pressure inside the uterus decreases when the baby is born.



Neural Control

• Some hormones are directly controlled by the nervous system. For example, the adrenal glands receive signals from the sympathetic nervous system. When the sympathetic nervous system is active, it sends signals to the adrenal glands to release epinephrine and norepinephrine as hormones, prolonging the effects of sympathetic activity.



Figure 12-4 Sympathetic control of adrenal gland.



Hormonal Control

• Other hormones are part of a hierarchy of hormonal control, where one gland is controlled by the release of hormones from another gland up the chain, which is controlled by another gland’s release of hormones up the chain. Orders are sent from one organ to another, like a relay race.

• Negative feedback controls the flow of orders via hormones from one part of the chain to the other.



Figure 12-5 Hormonal control of adrenal gland.



Humoral Control

• Some endocrine organs directly monitor the body’s internal environment by monitoring body fluids, such as blood, and then respond accordingly.

• Humoral is the term that pertains to body fluids or substances and therefore this is called humoral control. For example, the pancreas secretes insulin in response to rising blood sugar levels.



Figure 12-6 Humoral control of blood sugar levels.



From the Streets:Endocrine Emergencies

• Symptoms of endocrine emergencies can usually be assigned to one of two categories:– Symptoms of underproduction

Hyposecretion

– Symptoms of overproduction Hypersecretion



Endocrine Glands:The Hypothalamus

• The hypothalamus, located in the diencephalon, is an important link between the two control systems.

• The hypothalamus controls much of your physiology, including hunger, thirst, fluid balance, and body temperature to name a small number of its functions.



Endocrine Glands:The Hypothalamus

• The hypothalamus also acts as a “commander in chief” for the other glands in the endocrine system since it controls the pituitary gland, and thus, most other glands in the endocrine system.



The Pituitary

• The pituitary, also a part of the diencephalon, has been commonly known as the “master gland” because of its role in controlling other endocrine glands.

• The pituitary gland really acts only under orders from the hypothalamus.

• If the hypothalamus is the “commander in chief,” the pituitary is a high-ranking general.

• The pituitary is split into two segments, the posterior pituitary and the anterior pituitary.



The Posterior Pituitary

• The posterior pituitary is an extension of the hypothalamus. Hypothalamic neurons, specialized to secrete hormones instead of neurotransmitters, extend their axons through a stalk in the posterior pituitary.

• These neurons secrete two hormones, antidiuretic hormone (ADH) and oxytocin. While they are secreted by the pituitary, they are made by the hypothalamus.



Antidiuretic Hormone

• The name suggests exactly what it does, it decreases urination, which decreases fluid loss, increasing body fluid volume.

• ADH is secreted when the hypothalamus senses decreased blood volume or increased blood osmolarity (more solids suspended in blood).



Antidiuretic Hormone

• ADH circulates through the blood stream and targets the kidneys specifically, causing them to absorb more water.

• ADH is very important in long-term control of blood pressure, especially during dehydration.



Oxytocin

• Oxytocin is important in maintaining uterine contractions during labor and is involved in milk production in nursing mothers.

• Oxytocin’s function in males is unknown.



The Anterior Pituitary

• The anterior pituitary makes and secretes a number of hormones under hormonal control of the hypothalamus.

• The hypothalamus secretes a hormone that controls hormone secretion by the anterior pituitary, which usually controls the secretion of hormones by another endocrine gland (growth hormone is an exception).

• The hormone levels are controlled by negative feedback to both the pituitary and the hypothalamus.



Clinical Application:Stature Disorders

• Stature disorders are those that result in well below normal (dwarfism) or well above normal (gigantism or giantism) height. Some are caused by abnormalities in skeletal development or nutritional deficiencies, but growth hormone (GH) problems are often implicated.




• If GH secretion is insufficient during childhood, children don’t grow to normal height. If GH deficiency is diagnosed before closure of the growth zones of the long bones it can be treated with GH supplements, otherwise these children grow to be undersized adults.




• Oversecretion of GH during childhood results in very, very tall people. Robert Wadlow, one of the tallest men to ever live, according to The Guinness Book of World Records, was more than 8 feet tall. People with gigantism have many health problems, including a skeleton that can’t support them. Surgery and medication are the only treatments.




• If the oversecretion of GH starts after the bones have stopped growing the person doesn’t get taller but the tissue of the hands, feet, face, and many internal organs will continue to grow out of control causing pain and organ dysfunction. Most oversecretion is due to noncancerous pituitary tumors.



Table 12-3 Selected Hypothalamic and Pituitary Hormones.



Table 12-3 (continued) Selected Hypothalamic and Pituitary Hormones.



From the Streets:Vasopressin

• Antidiuretic hormone (ADH), also called vasopressin, is one of two hormones secreted by the posterior pituitary.

• ADH causes increased reabsorption of water in the kidneys and vasoconstriction of peripheral vessels.

• Both mechanisms increase blood pressure.



From the Streets:Vasopressin

• Vasopressin may be used in certain types of cardiac arrest as an alternative to epinephrine.



Figure 12-7 The hypothalamus, anterior and posterior pituitary glands, and their targets and associated hormones.



The Thyroid Gland

• The thyroid gland is located in the anterior portion of the neck and is butterfly-shaped.

• The thyroid gland secretes the hormones triiodothyronine (T3) and thyroxine (T4) under orders from the pituitary. The third hormone is calcitonin, involved in calcium storage.

• T3 and T4 contain iodine and control cell metabolism and growth.



The Thyroid Gland

• Over- or under-production cause a variety of clinical symptoms, because the level of these hormones is essential in controlling growth and metabolism of body tissues, particularly in the nervous system.

• Table salt contains iodine to ensure people get enough iodine in their diets to make thyroid hormones.



Parathyroid Glands

• The thyroid gland has two small pairs of glands, called the parathyroid glands, embedded in its posterior surface.

• They produce parathyroid hormone (PTH), which regulates the levels of calcium in the blood stream.

• If calcium levels get too low, the parathyroid glands are stimulated to release PTH, which stimulates bone dissolving cells and releases calcium into the blood stream.



Figure 12-8 The thyroid and parathyroid glands.



Figure 12-8 (continued) The thyroid and parathyroid glands.



Clinical Application: Hyperthyroidism

• Jenny was a healthy 25-year-old school teacher starting her first job when she began having strange symptoms, including a rapid heart rate, profuse sweating, and constant hunger. Initially, she thought the symptoms were caused by the stress of her new job and moving from home, but then other, more alarming, symptoms appeared.



Clinical Application: Hyperthyroidism

• Jenny became irritable and restless, developed insomnia, and couldn’t concentrate. Soon she couldn’t focus long enough to read the newspaper or get through a half hour sitcom. Her thoughts became so scattered she thought she might be going crazy so she made an appointment with her doctor and found out she had Graves’ disease, a disorder that causes oversecretion of the thyroid hormone.



Figure 12-9 The hypothalamus controls the anterior pituitary, which in turn controls the thyroid gland. Negative feedback loops prevent the oversecretion of hormones.



Table 12-4 Common Signs and Symptoms of Thyroid Disease



Figure 12-10 Graves’ disease results from an increase in the levels of circulating thyroid hormones.



Figure 12-11 Hypothyroidism results from a decrease in the levels of circulating thyroid hormones.



The Thymus Gland

• The thymus gland is located in the upper thorax.

• It plays an important function in the immune system.

• It produces a hormone, called thymosin, which helps with the maturation of white blood cells during childhood, to fight infection.



The Pineal Gland

• The tiny pineal gland is found within the diencephalon of the brain.

• Its full function remains unknown.• It has been shown to produce the

hormone melatonin which rises and falls during the waking and sleeping hours. It is believed that this hormone triggers our sleep by peaking at night and causing drowsiness.



The Pancreas

• The pancreas is responsible controlling blood sugar. – Glucose levels are important because all cells

need glucose for cellular respiration.– Blood glucose levels affect the fluid balance

of the cells.



The Pancreas

• Blood sugar rises – the pancreas releases insulin– Helps glucose get into cells– Causes excess glucose to be stored as

glycogen in the liver

• Blood sugar falls – the pancreas releases glucagon – Causes glucose to be released from the liver



Figure 12-13 Intravenous glucose administration may be required for patients with confirmed hypoglycemia.



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Clinical Application:Diabetes Mellitus

• Diabetes mellitus (DM) is a condition characterized by abnormally high blood glucose levels. Type 1 diabetes is caused by destruction of insulin-producing cells of the pancreas, resulting in inadequate insulin production. These patients require daily insulin injections.

• Type 2 diabetes is caused by insensitivity of the body’s tissues to insulin and can be treated with a carefully controlled diet and a weight loss regimen.




• In either type of DM, elevated blood sugar must be controlled because high glucose levels cause the kidneys to work overtime to secrete the excess sugar. Increased urination (polyuria), dehydration leading to increased thirst (polydipsia), and hunger are the most common symptoms.




• Untreated diabetes leads to weight loss as the body searches for other sources of energy. As abnormal cell metabolism breaks down muscle, acid is produced and blood acidity worsens, leading to tissue and organ damage. Lack of treatment will lead to coma and death.



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The Adrenal Glands

• The adrenal glands are a pair of small glands that sit on the kidneys, like baseball hats.

• The adrenal glands are split into two regions:– The adrenal cortex is the outer layer.– The adrenal medulla is the middle of the

gland.



Adrenal Medulla

• The adrenal medulla releases two hormones:– Epinephrine (formally known as adrenalin)– Norepinephrine (both a hormone and a

neurotransmitter)



Adrenal Medulla

• These hormones increase the duration of the effects of your sympathetic nervous system. The effects of hormones last longer than a neurotransmitter.

• Effects include increased heart rate, blood pressure, and respiration, along with profuse sweating and a dry mouth.



Adrenal Cortex

• The adrenal cortex makes dozens of steroid hormones, known collectively as adrenocorticosteroids, which are released under the direct stimulation of the anterior pituitary.

• Many of these hormones are so important that a decrease in production could be fatal relatively quickly.



Adrenal Cortex

• Each of these hormones has a specific function, including regulation of fluids, electrolytes, blood sugar, reproduction, secondary sex characteristics, cell metabolism, growth, and immune system function.



Clinical Application: Prednisone

• Prednisone is clinically important in the treatment of inflammation, organ rejection, and immune disorders. Prescription steroids are a two-edged sword because they have dangerous side effects including bone loss, weight gain, hair growth, fat deposits, and delayed wound healing.



Clinical Application: Prednisone

• This drug cannot be discontinued suddenly because the drug decreases adrenal cortex production. The adrenal cortex must be allowed to resume normal functions gradually – gearing up to secrete the proper amount of steroids.



The Gonads

• The gonads include– Testes– Ovaries

• Their chief function is to produce and store gametes – Eggs– Sperm

• They also produce a number of sex hormones which control reproduction– Testosterone in men– Estrogen in women



From the Streets:Disorders of the Adrenal Gland

• Hyperadrenalism (Cushing’s Syndrome)• Causes: Excessive adrenocortical activity.• Signs and symptoms• Assessment• Treatment



Figure 12-14 Facial features of Cushing’s syndrome.(Photo Researchers)



From the Streets:Disorders of the Adrenal Gland

• Adrenal insufficiency (Addison’s Disease)• Causes: Deficient adrenocortical activity• Signs and symptoms• Assessment• Treatment



Disorders of the Endocrine System: Anabolic Steroid Abuse

• Anabolic steroids cause large increases in muscle mass.

• Some athletes use them to increase performance, or to get big muscles faster than working out alone would produce.

• There are numerous side effects including changes in sperm production, enlarged breasts, and shrinking testicles in men.



Anabolic Steroid Abuse

• Women experience a deepening voice, decreased breast size, and excessive body hair growth.

• Use of steroids can lead to cardiovascular disease and lipidemia.

• Steroids may suppress immune response, and because they are illegal, can expose users to HIV and hepatitis B when sharing needles.

• Steroids have been linked to increased aggressiveness.



Hashimoto’s Disease

• Hashimoto’s disease is a form of hypothyroidism caused by an autoimmune attack of the thyroid gland.

• The cause is unknown. The body attacks the thyroid gland, causing inflammation and damage to the gland, leading to decreased production of thyroid hormones (hypothyroidism).

• The thyroid may swell, causing painful swallowing. It is most common in women 30 to 50-years-old and is treated with a daily synthetic hormone treatment.



Graves’ Disease

• Graves’ disease is an autoimmune disorder affecting the thyroid, stimulating an increased production of hormones, called hyperthyroidism.

• Symptoms include insomnia, bulging eyes, and jitteriness.

• Treatment involves decreasing hormone secretion by destroying the thyroid with radioactive iodine, or surgery if this is not effective. After treatment, patients will need synthetic thyroid hormone because the thyroid no longer functions properly, if at all.



Pheochromocytoma

• A pheochromocytoma is a tumor of the adrenal gland causing increased epinephrine secretion.

• The symptoms are similar to an adrenalin rush, including severe headaches, excess sweating, racing heart, anxiety, abdominal pain, heat intolerance, and weight loss.

• They are rarely cancerous but must be removed or the effects of excessive epinephrine production will be fatal.



Addison’s Disease

• Addison’s disease is caused by insufficient production of the adrenocorticosteroid cortisol. The deficiency causes weight loss, muscle weakness, fatigue, low blood pressure, and excessive skin pigmentation.

• Aldosterone may also be deficient. • Many cases of Addison’s are autoimmune.

It is treated with hormone replacement.



Cushing’s Syndrome

• Cushing’s syndrome is caused by oversecretion of cortisol.

• Symptoms include upper body obesity, round face, easy bruising, weakened bones, fatigue, high blood pressure, and high blood sugar.



Cushing’s Syndrome

• Women may have excessive facial hair and irregular periods while men have decreased fertility and sex drive. It may be a side effect of medical use of steroids, like prednisone, or may be due to primary tumors, lung tumors, adrenal tumors, or one of several genetic disorders.

• Treatment depends on the underlying cause. Hormone replacement may be required.



Figure 12-15 Examples of Endocrine Disorders. (A) A 6-year-old child with congenital hypothyroidism. (B) A patient with Cushing’s syndrome.



Figure 12-15 (continued) Examples of Endocrine Disorders. (C) A patient with exophthalmos, a symptom of hyperthyroidism (Graves’ disease). (Source: Custom Medical

Stock Photo, Inc.)



Figure 12-15 (continued) Examples of Endocrine Disorders. (D) A patient with a goiter. (Source: Custom Medical Stock Photo, Inc.)



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Snapshots from the Journey

• The endocrine system works together with the nervous system to regulate the activities of all the body systems. The endocrine system is linked to the nervous system but works very differently. The endocrine system secretes hormones that act very slowly on distant targets. Their effects are long lasting. Some organs, like the pancreas and the thyroid gland, function mainly to release hormones.




• However, many other organs, like the heart and stomach, can also release hormones. They aren’t considered endocrine glands because hormone release isn’t their primary role.




• Most hormones act on cells by binding to external receptors, causing changes in enzyme activity inside the target cell. Steroids, however, can enter cells and interact directly with DNA, which makes steroids very powerful.




• Hormone levels are controlled largely by negative feedback. When hormone levels rise, signals are transmitted to the endocrine organ releasing the hormone, telling the organ to decrease the amount of hormone released. Hormone levels will then decrease. The optimal level of the hormone is called the set point.




• If the signal brings a hormone back to set point, the action is called negative feedback. If the signal causes the hormone to get further away from set point, the action is positive feedback.




• Hormone levels can be regulated via three mechanisms: changes in the body’s internal environment (humoral), control by hormones released by another endocrine gland (hormonal), and direct control by the nervous system (neural).




• The hypothalamus, a part of the diencephalon, controls much of the endocrine system by controlling the pituitary gland.




• The pituitary gland has two parts: the posterior pituitary, which is part of the hypothalamus and actually secretes hypothalamic hormones (ADH and oxytocin), and the anterior pituitary, which secretes several different hormones under the influence of hormones from the hypothalamus.




• The hormones secreted by the anterior pituitary typically control other endocrine glands (growth hormone is an exception).




• Several other endocrine glands have important control functions. The thyroid gland secretes the iodine-containing hormones triiodothyronine (T3) and thyroxine (T4), which control growth and cellular metabolism. The pancreas secretes two hormones: insulin, which lowers blood sugar, and glucagon, which raises blood sugar.




• Diabetes is caused by a decrease in insulin secretion or decreased sensitivity to insulin. Very high blood sugar is the result.




• The adrenal glands are split into two parts. The adrenal medulla is an extension of the sympathetic nervous system, releasing epinephrine and norepinephrine as hormones during fight-or-flight response. The adrenal cortex releases many different adrenocorticosteroid hormones, which control reproduction, inflammation, tissue growth, and immunity.



Case Study

A 40-year-old patient presents to the emergency department with the following symptoms:– Recent weight loss– Generalized weakness– Excessive thirst and urination



Case Study

• Portions of his lab values show a blood glucose of 150 mg/dl and acidic urine and blood. He has a family history of diabetes, but this is the first time he’s presented with these symptoms.



Case Study Questions

• What type of diabetes does he have?• What organs will be affected if he is not

properly diagnosed and treated?• What treatment and lifestyle suggestions

would you give?



From the Streets

You are called to the home of the 40 year-old patient who presented to the ED 1 month ago. Family states that he did not follow up for diabetic treatment. You find him lying in bed slow to respond with rapid & deep breathing, hypotension, tachycardia, severely incontinent of urine, and pale, cool, & clammy skin. His breath has a fruity odor. His blood glucose is 600 mg/dl (normal range 60—120 mg/dl).



From the Streets Questions

• What is his most likely diagnosis? • What is the term for his rapid and deep

respiratory pattern? • Why is the patient hypotensive? • What is his prognosis?



From the Streets Questions

• What is his most likely diagnosis? Diabetic Ketoacidosis (DKA)

• What is the term for his rapid and deep respiratory pattern? Kussmaul respirations

• Why is the patient hypotensive? Polyuria (glucosuria) has lead to dehydration

• What is his prognosis? This is life threatening, he needs supportive measures and emergency transport.



End of ChapterReview Questions

___ADH___Insulin___Glucagon___Oxytocin___Epinephrine___Thyroxine___Prolactin___ACTH___TSH___Growth Hormone

a. Decreases blood sugarb. Increases thyroid hormone

secretionc. Regulates cell metabolismd. Increases steroid releasee. Increases uterine contractionsf. Decreases urinationg. Prolongs sympathetic responseh. Stimulates tissue growthi. Increases blood sugarj. Increases milk production in

females

Match the Hormone with the Description




1. ADH stands for:a. Antidiuretic hormoneb. Androdoginin hormonec. American Department of Healthd. All-diglyceride hormone




2. The “master gland” is the:a. Adrenalb. Pituitaryc. Pineald. Pancreas




3. The thymus gland’s main function is for:a. Reproductionb. Growthc. Immunityd. RBC levels




4. The pineal gland is located in/on the:a. Kidneysb. Brainc. Thoraxd. Abdomen




5. Glucagon performs the opposite action of:a. Glucoseb. Insulinc. ATPd. WBC’s




6. Some of the following disorders are associated with weight gain. Which ones?

I. Type II diabetesII. HyperthyroidismIII. Cushing’s syndromeIV. Addison’s disease

– I, II– I, II, III– I, II, IV– I, III




7. If an adult patient is treated for gigantism by removal of their pituitary gland, which hormone would have to be replaced with drug therapy.a. Cortisolb. Melatoninc. Thyroid-stimulating hormoned. Insulin




1. Glucagon _________ blood sugar.2. Thyroxine __________ cell metabolism.3. _________ increases uterine

contractions.4. Sympathetic response is enhanced by

epinephrine secreted by the _______.5. Increased secretion of aldosterone, a

corticosteroid, could be caused by a tumor on the _________ or __________ glands.




6. Damage to the ______ in the brain could cause widespread endocrine abnormalities.

7. This hormone is less important than in adults than children _____________.




1. Compare and contrast neurotransmitters and hormones.

2. Explain negative feedback and its role in controlling hormone levels.

3. Discuss why the use of anabolic steroids should be outlawed for performance enhancement.

4. What is the difference between neural control and humoral control of endocrine glands?

the endocrine system: the body’s other control system

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