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Chapter 16: The
Endocrine System
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Chapter Objectives
• Definition hormones.
• Comparison between steroid and amino acid hormones.
• The endocrine system.
• Hormones produced by the endocrine glands and
functions of each.
• Roots pertaining to the endocrine system.
• Main disorders of the endocrine system.
• Abbreviations used in endocrinology.
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Key Terms
Normal Structure and Function
adrenal gland
A gland on the superior surface of the kidney. The outer region
(cortex) secretes steroid hormones; the inner region (medulla)
secretes epinephrine (adrenaline) and norepinephrine
(noradrenaline) (root: adren/o)
endocrine
Pertaining to a ductless gland that secretes directly into the blood
hormone
A secretion of an endocrine gland. A substance that travels in the
blood and has a regulatory effect on tissues, organs, or glands.
hypophysis
The pituitary gland (root: hypophys); named from hypo, meaning
“below,” and physis, meaning “growing,” because the gland grows
below the hypothalamus
hypothalamus
A portion of the brain that controls the pituitary gland and is active in
maintaining homeostasis
pancreatic islets
Clusters of endocrine cells in the pancreas that secrete hormones to
regulate sugar metabolism; also called islets of Langerhans or islet
cells (root insul/o means “island”)
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Key Terms
Normal Structure and Function (cont’d)
parathyroid glands
Small endocrine glands on the posterior thyroid that act to
increase blood calcium levels; there are usually four to six
parathyroid glands (root: parathyr/o, parathyroid/o); the name
literally means “near the thyroid”
pineal gland
A small gland in the brain. Appears to regulate mood, daily
rhythms, and sexual development in response to environmental
light. Secretes the hormone melatonin
pituitary gland
A small endocrine gland at the base of the brain. The anterior lobe
secretes growth hormone and hormones that stimulate other
glands; the posterior lobe releases ADH and oxytocin
manufactured in the hypothalamus
prostaglandins
A group of hormones produced throughout the body that have a
variety of effects, including stimulation of uterine contractions and
regulation of blood pressure, blood clotting, and inflammation
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Key Terms
Normal Structure and Function (cont’d)
receptor
A site on the cell membrane or within the cell to which a
substance, such as a hormone, attaches
steroid hormone
A hormone made from lipids and including the sex hormones and
the hormones of the adrenal cortex
target tissue
The specific tissue on which a hormone acts; may also be called
the target organ
thyroid gland
An endocrine gland on either side of the larynx and upper trachea.
It secretes hormones that affect metabolism and growth and a
hormone (calcitonin) that regulates calcium balance (root: thyr/o,
thyroid/o).
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Roots Pertaining to the Endocrine System
Definition of
Example
Root
Meaning
Example
endocrin/o
endocrine glands
or system
endocrinopathy
any disease of the
endocrine glands
pituitar
pituitary gland,
hypophysis
pituitarism
condition caused by
any disorder of
pituitary function
hypophys
pituitary gland,
hypophysis
hypophysial
pertaining to the
pituitary gland
thyr/o, thyroid/o
thyroid gland
thyrolytic
destroying the thyroid
gland
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Roots Pertaining to the Endocrine System
(cont’d)
Definition of
Example
Root
Meaning
Example
parathyr/o,
parathyroid/o
parathyroid
gland
hyperparathyroidism
overactivity of a
parathyroid gland
adren/o, adrenal/o
adrenal gland,
epinephrine
adrenergic
activated (erg) by
or related to
epinephrine
(adrenaline)
adrenocortic/o
adrenal cortex
adrenocorticotropic
acting on the
adrenal cortex
insul/o
pancreatic islets
insular
pertaining to islet
cells
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Key Terms
Disorders
acromegaly
Overgrowth of bone and soft tissue, especially in the hands, feet, and
face, caused by an excess of growth hormone in an adult. The name
comes from acro meaning “extremity” and megal/o meaning
“enlargement”
Addison disease
A disease resulting from deficiency of adrenocortical hormones. It is
marked by darkening of the skin, weakness, and alterations in salt
and water balance
adenoma
A neoplasm of a gland
congenital
hypothyroidism
A condition caused by congenital lack of thyroid secretion and marked
by arrested physical and mental development; formerly called
cretinism (KRĒ-tin-izm)
Cushing disease
Overactivity of the adrenal cortex resulting from excess production of
ACTH by the pituitary
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Key Terms
Disorders (cont’d)
Cushing syndrome
A condition resulting from an excess of hormones from the adrenal
cortex. It is associated with obesity, weakness, hyperglycemia,
hypertension, and hirsutism (excess hair growth).
diabetes insipidus
A disorder caused by insufficient release of ADH from the posterior
pituitary. It results in excessive thirst and production of large
amounts of very dilute urine. The word insipidus means “tasteless,”
referring to the dilution of the urine.
diabetes mellitus
A disorder of glucose metabolism caused by deficiency of insulin
production or failure of the tissues to respond to insulin. Type 1
results from autoimmune destruction of pancreatic islet cells; it
generally appears in children and requires insulin administration.
Type 2 generally occurs in obese adults; it is treated with diet,
exercise, drugs to improve insulin production or activity, and
sometimes insulin. The word mellitus comes from the Latin root for
honey, referring to the sugar content of the urine.
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Key Terms
Disorders (cont’d)
exophthalmos
Protrusion of the eyeballs, as seen in Graves disease
gigantism
Overgrowth caused by an excess of growth hormone from the
pituitary during childhood; also called giantism
glycated
hemoglobin
(HbA1c) test
A test that measures the binding of glucose to hemoglobin during the
lifespan of a red blood cell. It reflects the average blood glucose level
over 2 to 3 months and is useful in evaluating long-term therapy for
diabetes mellitus. Also called A1c test.
glycosuria
Excess sugar in the urine
goiter
Enlargement of the thyroid gland. May be toxic or nontoxic. Simple
(nontoxic) goiter is caused by iodine deficiency.
Graves disease
An autoimmune disease resulting in hyperthyroidism. A prominent
symptom is exophthalmos (protrusion of the eyeballs). Also called
diffuse toxic goiter.
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Key Terms
Disorders (cont’d)
hyperglycemia
Excess glucose in the blood
hypoglycemia
Abnormally low level of glucose in the blood
insulin shock
A condition resulting from an overdose of insulin, causing
hypoglycemia
ketoacidosis
Acidosis (increased acidity of body fluids) caused by an excess of
ketone bodies, as in diabetes mellitus; diabetic acidosis
metabolic syndrome
A state of hyperglycemia caused by cellular resistance to insulin, as
seen in type 2 diabetes, in association with other metabolic
disorders; syndrome X or insulin resistance syndrome
myxedema
A condition caused by hypothyroidism in an adult. There is dry, waxy
swelling most notable in the face
panhypopituitarism
Underactivity of the entire pituitary gland
tetany
Irritability and spasms of muscles; may be caused by low blood
calcium and other factors
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Supplementary Terms
Normal Structure and Function
sella turcica
A saddle-shaped depression in the sphenoid bone that
contains the pituitary gland (literally means “Turkish saddle”)
sphenoid bone
A bone at the base of the skull that houses the pituitary gland
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Supplementary Terms
Symptoms and Conditions
adrenogenital
syndrome
Condition caused by overproduction of androgens from the adrenal
cortex, resulting in masculinization; may be congenital or acquired,
usually as a result of an adrenal tumor
Conn syndrome
Hyperaldosteronism caused by an adrenal tumor
craniopharyngioma
A tumor of the pituitary gland
Hashimoto disease
A chronic thyroiditis of autoimmune origin
impaired glucose
tolerance (IGT)
High blood glucose levels after glucose intake that may signal
borderline diabetes mellitus
ketosis
Accumulation of ketone bodies, such as acetone, in the body. Usually
results from deficiency or faulty metabolism of carbohydrates, as in
cases of diabetes mellitus and starvation.
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Supplementary Terms
Symptoms and Conditions (cont’d)
multiple endocrine
neoplasia (MEN)
A hereditary disorder that causes tumors in several endocrine
glands; classified according to the combination of glands involved
pheochromocytoma
A usually benign tumor of the adrenal medulla or other structures
containing chromaffin cells (cells that stain with chromium salts);
phe/o means “brown” or “dusky.” The adrenal tumor causes
increased production of epinephrine and norepinephrine.
pituitary apoplexy
Sudden massive hemorrhage and degeneration of the pituitary
gland associated with a pituitary tumor. Common symptoms include
severe headache, visual problems, and loss of consciousness.
seasonal affective
disorder (SAD)
A mood disorder with lethargy, depression, excessive need for sleep,
and overeating that generally occurs in winter. Thought to be related
to melatonin levels as influenced by environmental light.
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Supplementary Terms
Symptoms and Conditions (cont’d)
Simmonds disease
Hypofunction of the anterior pituitary (panhypopituitarism), usually
because of an infarction; pituitary cachexia (ka-KEK-sē-a)
thyroid storm
A sudden onset of the symptoms of thyrotoxicosis occurring in
patients with hyperthyroidism who are untreated or poorly treated.
May be brought on by illness or trauma. Also called thyroid crisis.
thyrotoxicosis
Condition resulting from overactivity of the thyroid gland. Symptoms
include anxiety, irritability, weight loss, and sweating. The main
example of thyrotoxicosis is Graves disease.
von Recklinghausen
disease
Degeneration of bone caused by excess production of parathyroid
hormone. Also called Recklinghausen disease of bone.
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Supplementary Terms
Diagnosis and Treatment
fasting plasma glucose (FPG)
Measurement of glucose in the blood after a
fast of at least 8 hours. A reading ≥126 mg/dL
indicates diabetes. Also called fasting blood
glucose (FBG) or fasting blood sugar (FBS)
free thyroxine index
(FTI, T7)
Calculation based on the amount of T4
present and T3 uptake, used to diagnose
thyroid dysfunction
oral glucose tolerance test (OGTT)
Measurement of glucose levels in blood
plasma after administration of a challenge
dose of glucose to a fasting patient. Used to
measure patient's ability to metabolize
glucose. A value ≥200 mg/dL in the 2-hour
sample indicates diabetes
radioactive iodine uptake test (RAIU)
A test that measures thyroid uptake of
radioactive iodine as an evaluation of thyroid
function
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Supplementary Terms
Diagnosis and Treatment (cont’d)
radioimmunoassay
(RIA)
A method of measuring very small amounts of a substance,
especially hormones, in blood plasma using radioactively labeled
hormones and specific antibodies
thyroid scan
Visualization of the thyroid gland after administration of radioactive
iodine
thyroxine-binding
globulin (TBG) test
Test that measures the main protein that binds T4 in the blood
transsphenoidal
adenomectomy
Removal of a pituitary tumor through the sphenoid sinus (space in
the sphenoid bone)
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Abbreviations
A1c
Glycated hemoglobin (test)
ACTH
Adrenocorticotropic hormone
ADH
Antidiuretic hormone
BS
Blood sugar
CSII
Continuous subcutaneous insulin infusion
DM
Diabetes mellitus
FBG
Fasting blood glucose
FBS
Fasting blood sugar
FPG
Fasting plasma glucose
FSH
Follicle-stimulating hormone
FTI
Free thyroxine index
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Abbreviations (cont’d)
GDM
Gestational diabetes mellitus
GH
Growth hormone
HbA1c
Hemoglobin A1c; glycated hemoglobin
131I
Iodine-131 (radioactive iodine)
IFG
Impaired fasting blood glucose
IGT
Impaired glucose tolerance
LH
Luteinizing hormone
MEN
Multiple endocrine neoplasia
NPH
Neutral protamine Hagedorn (insulin)
OGTT
Oral glucose tolerance test
PRL
Prolactin
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Abbreviations (cont’d)
PTH
Parathyroid hormone
RAIU
Radioactive iodine uptake
RIA
Radioimmunoassay
SIADH
Syndrome of inappropriate antidiuretic hormone (secretion)
T1DM
Type 1 diabetes mellitus
T2DM
Type 2 diabetes mellitus
T3
Triiodothyronine
T4
Thyroxine; tetraiodothyronine
T7
Free thyroxine index
TBG
Thyroxine-binding globulin
TSH
Thyroid-stimulating hormone
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Hormones
• Self-regulating system
• Affect:
– Growth
• Production
– Extremely small
amounts
– Highly potent
– Metabolism
– Behavior
• Two categories:
– Steroid (lipids)
– Amino acid
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Endocrine Glands
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Pituitary
• Also known as hypophysis
• Located beneath brain
• Divided into two lobes:
– Anterior
• Releases six hormones
– Posterior
• Releases two hormones
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Thyroid and Parathyroids
• Thyroid gland
– Located on either side of larynx and upper trachea
– Two lobes
– Secretes mixture of hormones
• Parathyroid glands
– Located at posterior surface of thyroid
– Affect calcium metabolism
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Thyroid Gland
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Adrenal Glands
• Hormones produced involved in body’s response to stress
• Located atop each kidney
• Divided into two regions
– Outer cortex
– Inner medulla
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Adrenal Glands (cont’d)
– Outer cortex produces:
• Steroid hormones
• Cortisol
• Aldosterone
• Sex hormones
– Inner medulla produces:
• Epinephrine
• Norepinephrine
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Pancreas
• Islet cells produce two hormones:
– Insulin
• Increases cellular use of glucose
• Decreases sugar levels in blood
– Glucagon
• Decreases cellular use of glucose
• Increases sugar levels in blood
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Other Endocrine Tissues
• Pineal
– Regulates mood, daily rhythms, sexual development
in response to light
• Thymus
– Secretes thymosin
• Gonads
– Secrete sex hormones
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Other Endocrine Tissues (cont’d)
• Prostaglandins
– Group of hormones produced by many cells
– Variety of effects
• Uterine contractions
• Inflammatory response
• Vasomotor activities
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Clinical Aspects of Endocrine System
General
• Endocrine diseases result from:
–
Hypersecretion
–
Hyposecretion
–
Secretion at wrong time
–
Failure of target tissue to respond
• Causes may originate:
–
In gland itself
–
With hypothalamus or pituitary failing to release proper amount
of hormone stimulators
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Clinical Aspects of Endocrine System
Pituitary
• Pituitary adenoma usually increases secretion of growth
hormone
– Excess in children causes gigantism
– Excess in adults causes acromegaly
• Treatment: surgery, drugs to reduce hormone level in
blood
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Clinical Aspects of Endocrine System
Pituitary (cont’d)
• Panhypopituitarism
–
Hypofunction of pituitary
–
Caused by tumor or interruption of gland’s blood supply
–
Widespread effects
• Lack of ADH
–
Results in diabetes insipidus
• Kidneys with diminished ability to conserve water
• Symptoms include: polyuria, polydipsia
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Clinical Aspects of Endocrine System
Thyroid
• Deficiency of thyroid hormone causes:
– In infants
• Physical retardation
• Mental retardation
• Congenital hypothyroidism
– In adults
• Myxedema
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Clinical Aspects of Endocrine System
Thyroid (cont’d)
• Hyperthyroidism
– Common form is Graves disease
– May result in goiter (enlarged thyroid)
• Not always results from thyroid malfunction
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Clinical Aspects of Endocrine System
Parathyroids
• Overactivity causes high level of calcium in blood
– Calcium obtained from bones
– Possible development of kidney stones
• Underactivity results in decreased calcium
– May cause:
• Tingling
• Numbness
• Tetany
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Clinical Aspects of Endocrine System
Adrenals
• Addison disease = hypofunction of adrenal cortex
– Caused by:
• Autoimmune destruction of gland
• ACTH deficiency
– Results in water loss, low blood pressure, electrolyte
imbalance, weakness, nausea, increase of brown
pigmentation
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Clinical Aspects of Endocrine System
Adrenals (cont’d)
• Cushing syndrome = excess of adrenal cortisol hormones
– Caused by:
• Therapeutic administration of steroid hormones
• Tumor
– Results in: moon-shaped face, localized obesity,
weakness, hirsutism, fluid retention
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Clinical Aspects of Endocrine System
Pancreas and Diabetes
• Diabetes mellitus
– Most common endocrine disorder
– Failure to use glucose effectively
– Excess glucose causes hyperglycemia
– Increased urination causes glycosuria
– Two types:
• Type 1
• Type 2
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Clinical Aspects of Endocrine System
Pancreas and Diabetes (cont’d)
– Diagnosis: measure glucose levels in blood plasma
– Treatment:
• Monitor blood sugar, insulin treatment (type 1)
• Glycated hemoglobin test
• Exercise and weight loss, insulin treatment (type
2)
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Type 1 Diabetes Mellitus
• Juvenile-onset or insulin-dependent
– Usually appears in children and teenagers
– Caused by failure of pancreatic islets to produce
insulin
– For proper management:
• Monitor blood sugar levels
• Give insulin in divided doses
• Regulate diet
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Type 2 Diabetes Mellitus
• Accounts for 90% of cases
• Initiated by cellular resistance to insulin
• May result in:
–
Metabolic syndrome
–
Hypoglycemia
–
Insulin shock
• Diagnosed by measuring levels of glucose in blood plasma
• Most cases linked to obesity
• Another form is gestational diabetes mellitus
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Pretest
1. The secretions of the endocrine glands are called:
(a) enzymes
(b) sera
(c) lymph
(d) hormones
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Pretest
1. The secretions of the endocrine glands are called:
(a) enzymes
(b) sera
(c) lymph
(d) hormones
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Pretest
2. The small gland in the brain that controls other glands is
the:
(a) pituitary
(b) thymus
(c) appendix
(d) corpus luteum
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Pretest
2. The small gland in the brain that controls other glands is
the:
(a) pituitary
(b) thymus
(c) appendix
(d) corpus luteum
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Pretest
3. The glands that are located above the kidneys are the:
(a) thyroids
(b) follicles
(c) adrenals
(d) fimbriae
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Pretest
3. The glands that are located above the kidneys are the:
(a) thyroids
(b) follicles
(c) adrenals
(d) fimbriae
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Pretest
4. Gigantism results from overproduction of:
(a) growth hormone
(b) oxytocin
(c) erythropoietin
(d) prolactin
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Pretest
4. Gigantism results from overproduction of:
(a) growth hormone
(b) oxytocin
(c) erythropoietin
(d) prolactin
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Pretest
5. Diabetes mellitus involves the hormone insulin, which is
made by the:
(a) thymus
(b) seminal vesicle
(c) kidney
(d) pancreas
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Pretest
5. Diabetes mellitus involves the hormone insulin, which is
made by the:
(a) thymus
(b) seminal vesicle
(c) kidney
(d) pancreas
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Pretest
6. A goiter involves the:
(a) adrenal
(b) zygote
(c) calyx
(d) thyroid
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Pretest
6. A goiter involves the:
(a) adrenal
(b) zygote
(c) calyx
(d) thyroid
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