endocrine system chapter 14 lisa ochs rn, bsn 2008
TRANSCRIPT
Endocrine System
Chapter 14
Lisa Ochs RN, BSN 2008
Endocrine System
Regulates most organ systems throughout the body
Communicates through chemical signals called hormones
Actions are usually slower and longer lasting
Composed of endocrine glands
Glands of the
endocrine system
Endocrine glands
Endocrinology is the study of the endocrine system and its functions
Secrete chemical substances called hormones
Hormones are secreted directly into the blood stream (no ducts)
Hormones
Chemical messengers that influence or control the activities of other tissues or organs
Generally effect metabolic processes involving carbohydrates, lipids and fats
Also participate in growth and reproduction and water/ electrolyte balance
Hormones
Classification Proteins
Or protein- related substancesAlmost all hormones are proteins
SteroidsHormones secreted from the adrenal cortex
and sex glands
Targets
Target tissues or target organs are the specific sites where hormones bind
Targets may be close to or far from endocrine gland
Each endocrine gland may have many targets (more targets, more widespread or generalized effects)
Hormone Receptors
Hormones interact with receptor sites on their target tissues
The receptors are either located on the cell membrane (membrane receptors) or within the cell (intracellular receptors)
Each hormones binds with a specific receptor- lock and key theory (so that each hormone affects only certain cells); ensures specificity
Hormone Receptors
Protein hormonesUse membrane receptorsWhen the hormone binds with its receptor, a
second messenger is producedThis second messenger activates enzymes
within the cell
Hormone Receptors
Steroid hormonesUse intracellular receptorsSteroid hormones are lipid soluble (pass
through the cell membrane) Bind to receptors in the nucleus to create a
steroid-receptor complexThis complex stimulates protein synthesis and
alters cellular function
Figure 14-2 What hormones do. A, Hormones are aimed at target tissues or target organs. B, Protein hormones and membrane receptors. C, Steroid hormones and intracellular receptors.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.
Control of Hormone Secretions
Negative FeedbackBiorhythmsCentral Nervous System
Negative Feedback
Information about the hormone or its effects is sent back to the gland that secretes that hormone
Ex. Insulin secretion Blood glucose increases… insulin released
from pancreas… glucose moves into the cells, blood glucose falls… less insulin is released
Figure 14-3 Negative feedback control. A, Increased blood glucose levels trigger the release of insulin from the pancreas. B, Decreased blood glucose levels cause the pancreas to decrease its secretion of insulin.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.
Insulin is released in response to elevations in
plasma glucose. requires iodine for its synthesis. increases the concentration of glucose
in the blood. is classified as a catecholamine.
Biorhythms
A rhythmic (patterned) secretion of a hormone
Some hormones follow a circadian rhythm (24 hour cycle) or monthly cycle (female reproductive hormones)
May be disturbed by alterations in sleep-wake patterns (shift work, travel)
CNS Control
Activation of the hypothalamus Stimulation of the sympathetic nervous
system (fight or flight) A person’s emotional state may also affect
hormone secretion (especially stress)
Glands
Pituitary gland
Also called the hypophysis About the size of a pea; “Master Gland” Divided into lobes- anterior and posterior Secretions from the anterior lobe is controlled
by the hypothalamus (considered a gland because it secretes several hormones); releasing hormones and release-inhibiting hormones
Pituitary Gland
Anterior Pituitary Gland Also called the adenohypophysis (adeno-
means glandular) Secretes six major hormones; control many
other glands and affect many organ systems Prolactin, ACTH, growth hormone,
gonadotropins, TSH
Growth Hormone Also called somatotropin or somatotrophic
hormone Primarily affects skeletal muscle and long bones;
determines a persons size and height Also affects protein synthesis and use of fats for
energy; causes glucose levels to rise (stimulates conversion of proteins to glucose)
Secreted during periods of exercise, sleep and hypoglycemia
Pituitary Gland
Gigantism- caused by
hypersecretion of growth hormone
Acromegaly is a syndrome that results when the pituitary gland produces excess growth hormone (hGH) after epiphyseal plate closure at puberty.
Dwarfism- caused by
hyposecretion of growth hormone
Here- primordial dwarfism, a rare condition
Prolactin (PRL) Also called lactogenic hormone Promotes milk production in women Stimulates growth of mammary glands and
stimulates milk production after childbirth
Pituitary Gland
Tropic hormones Tropic hormones control or affect other glands Usually in end in –tropin or –tropic
Thyrotropin also called thyroid stimulating hormone (TSH); stimulates the thyroid gland to release hormones
Pituitary Gland
Tropic hormones Adrenocorticotropic hormone (ACTH)
causes the adrenal glands to secrete steroids
Gonadotropic hormones target the sex glands (gonads); include follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
Pituitary Gland
Posterior pituitary gland An extension of the hypothalamus Composed of nervous tissue, also called the
neurohypophysis Two hormones are produced in the
hypothalamus and stored in the posterior pituitary until needed; antidiuretic hormone and oxytocin
Pituitary Gland
Posterior pituitary gland Antidiuretic Hormone (ADH)
Released by the body to conserve waterCauses the kidney to reabsorb water from the
urine and return it to the bloodReleased in response to increased blood
concentration (dehydration, decreased volume, trauma, some drugs); alcohol inhibits ADH
Also called vasopressin, causes blood vessels to constrict (and therefore elevate BP)
Pituitary Gland
Posterior pituitary gland Antidiuretic Hormone (ADH)
If ADH is absent, profound diuresis will occur (diuresis means urine production); person may excrete up to 25 liters of urine per day; called diabetes insipidus
Excessive amounts of ADH will cause the body to retain water and certain electrolytes may be “washed out”- especially sodium (dilutional hyponatremia); called syndrome of inappropriate ADH (SIADH)
Pituitary Gland
Posterior pituitary gland Oxytocin
Targets the uterus and mammary glandsStimulates the uterine muscles to contract
during laborBreastfeeding stimulates the release of
oxytocin; causes contraction of the smooth muscles around the mammary ducts and releases breast milk; termed milk let-down reflex
Pituitary Gland
Pituitary Gland
New research has discovered a third hormone released from the posterior pituitary gland- secretin Already known to be secreted by the intestines Released in response to increased concentration of
solutes in the blood (think dehydration) Promotes secretion of ADH “and appears to have
direct water-conserving effects in the kidney as well”
From Jessica Y. S. Chu, et al. (2009) Proceedings of the National Academy of Science September 15, 2009 vol. 106 no. 37 15961-15966
Third lobe Tiny third lobe secretes melanocyte
stimulating hormone Stimulates the melanocytes in the skin and
causes darkening of the skin
Pituitary Gland
Thyroid Gland
Largest endocrine gland Located on the anterior neck; butterfly
shaped- two lobes connected by the isthmus
Composed of follicles that secrete triiodothyronine (T3) and tetraiodothyronine (T4 or thyroxine)
Thyroid hormones regulate all phases of metabolism and are necessary for the proper functioning of other hormones
Necessary for the maturation of the nervous system and normal growth and development
Thyroid Gland
Hypothyroidism Results in a condition called myxedemaSlowed metabolic state- slow heart rate, slowed
peristalsis (constipation), low body temperature, low energy, hair loss, weight gain, thickened skin
Cretinism is a congenital absence of thyroid gland; infant will fail to develop physically and mentally
Thyroid Gland
Typical patient with hypothyroidism. Note the puffiness in the face, coarse, thin hair and obesity
Cretinism- congenital lack of thyroid
hormone. Treatment includes replacement of
thyroid hormone and must be started within the first 6 weeks of life or permanent disability
will occur
Hyperthyroidism Excessive secretion of thyroid hormone
results in increased metabolic state; increased heart rate, increased peristalsis (diarrhea), elevated body temp (heat intolerance), hyperactivity, weight loss
Graves’ disease is a common type of hyperthyroidism; characterized by exophthalmia (caused by increased pressure behind the eyeball, which causes it to protrude out of the socket )
Thyroid Gland
Patient with exophthalmia, commonly seen in Graves’ disease. May also be seen in patients with normal functioning thyroid
gland (called euthyroid Graves’ disease)
Regulation of Secretion
Hypothalamus secretes a releasing hormone… stimulates the anterior pituitary to secrete TSH… TSH stimulates the thyroid gland to secrete T3 and T4… when blood levels of thyroid hormones are adequate, negative feedback prevents further secretion
Negative feedback loop
controlling thyroid
hormone secretion
Thyroid and Iodine
Iodine is required by the thyroid gland to synthesize T3 and T4
The iodine comes from dietary sources Tetraiodthyronine (thyroxine) contains 4
iodine atoms, triiodothyronine contains 3 iodine atoms
Iodine Deficiency
When there is a deficiency in the amount of iodine in the diet, the thyroid gland will enlarge
Iodine is needed to produce T3 and T4; without it, the negative feedback loop will not function to stop the secretion of TSH; persistent stimulation by TSH causes the thyroid gland to enlarge, called a goiter
Endemic goiter,
resulting from lack of iodine
in the diet
Parathyroid Glands
Situated along the posterior surface of the thyroid gland
Secrete parathyroid hormone (PTH); stimulated by low blood calcium levels
PTH target organs- bone, intestine, kidneys
Function is to elevate blood calcium levels
Parathyroid Glands
PTH elevates blood calcium three ways: Increases the release of calcium from bone
tissue; stimulates osteoclasis so calcium moves from the bone into the blood
Stimulates the kidneys to reabsorb calcium from the urine; causes the kidneys to increase excretion of phosphate (inverse relationship)
Increases absorption of calcium from the digestive tract; requires vitamin D
Figure 14-6 Parathyroid glands and the three target organs of PTH.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.
Parathyroid hormone (PTH)
stimulates osteoclastic activity. is released in response to decreasing
amounts of plasma calcium. increases plasma calcium. All of the above
Blood Calcium Blood calcium levels are also influenced by
calcitonin Secreted by the thyroid gland in response
to elevated blood calcium levels; calcitonin lowers calcium levels
Stimulates osteoblastic activity so calcium moves from the blood and into the bone and increases excretion of calcium in the urine.
Antagonistic to PTH
So…
High blood calcium levels stimulate secretion of ____________ and inhibit secretion of ____________.
Low blood calcium levels stimulate secretion of ____________ and inhibit secretion of ____________.
Hypocalcemia
Lack of calcium causes nerve and muscle membranes to become unstable and continuously fire electrical impulses; causes tetany
Hypocalcemic tetany that involves the muscles of respiration can be fatal; usually affects extremities
Hypocalcemic carpal spasm
Hypercalcemia
Patient develops hyperparathyroidism in response to injury to the parathyroid (usually a tumor)
PTH stimulates osteoclasis (Ca++ moves from bone to blood); excess Ca++ is excreted in the urine (can lead to kidney stones); can also affect CNS, cause slow heart rate, digestive problems (anorexia and constipation)
Adrenal Glands
Two small glands located above the kidneys
Consist of two regions- inner medulla and outer cortex; each secrete different hormones
Figure 14-8A A, The adrenal glands: adrenal medulla and the adrenal cortex.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.
Adrenal medulla
Inner region of the adrenal gland- part of the sympathetic nervous system (“fight or flight”)
Secrete epinepherine (adrenaline) and norepinepherine
Classified as catecholamines- help the body respond to stress
Catecholamines
Elevate BP; increase HR Convert glycogen to glucose (more available
to the cells) Increase metabolic rate (create more energy) Cause bronchodilation (more air to lungs) Dilate blood vessels to heart and muscles;
constrict to digestive tract
Adrenal Cortex
Outer region of the adrenal gland Secretes steroids (lipid soluble hormones) Three types:
Glucocorticoids (sugar)Mineralocorticoids (salt)Sex hormones (sex)
Adrenal cortical hormones are essential to life- must be replaced if adrenal cortex is not functioning
Glucocorticoids
Affect carbohydrates- convert amino acids into glucose (gluconeogenesis); helps to maintain blood glucose levels
Also affect protein and fat metabolism when needed for energy
Primary glucocorticoid is cortisol
Cortisol
Cortisol is released in response to stress (physiological stress- disease, injury, infection, pregnancy, as well as emotional stress)
Has an antiinflammatory effects; can be used to treat inflammation (allergic responses, arthritis); drugs like prednisone mimic cortisol’s effects
Cortisol Secretion
Hypothalamus secretes a releasing hormone… stimulates anterior pituitary gland to secrete ACTH (adrenocorticotropic hormone)… stimulates the adrenal cortex to secrete cortisol.
Elevated cortisol levels inhibit further secretion of ACTH (negative feedback)
Which of the following is least descriptive of the adrenal cortex?
Synthesizes iodine-containing hormones
Is a steroid-secreting gland Is responsive to ACTH Secretes cortisol, aldosterone, and
testosterone
Mineralocorticoids
Primary mineralocorticoid is aldosterone Very important for regulating blood volume and
blood pressure, and in regulating the concentration of electrolytes
Often called the salt-retaining hormone Reabsorbs sodium and water and eliminates
potassium in the urine Discussed in Chapter 24
Sex Hormones
Female hormones- estrogens Male homones- androgens (testosterone)
Discussed in Chapter 26
Adrenal Hyposecretion
Adrenal cortical insufficency, Addison’s disease
Characterized by: generalized weakness, muscle atrophy, bronzing of skin, severe loss of fluids and electrolytes. Can lead to hypovolemia, shock and death
Treatment: steroids, fluid and electrolyte replacement
Addison’s DiseaseDeficiency in the secretion of adrenal cortex hormones (cortisone and aldosterone). Symptoms include fatigue, weakness, weight loss, depression and hyperpigmentation (as seen above)
President John F. Kennedy had Addison’s disease.
Cushing’s syndrome Caused by: hypersecretion of ACTH or
cortisol, or by administration of steroids like prednisone
Characterized by: truncal obesity, moon face, buffalo hump, hirsutism, thin skin that bruises easily, bone loss & muscle weakness
Adrenal Hypersecretion
Cushing’s syndromeCushing’s is caused by increased level of cortisol. Symptoms include weight gain, fatigue, headache and the “moon face” appearance of the patient. (Clinically, to distinguish moon face from an obese face is the distribution of fat- in moon face, the fat distribution is higher and the ears are not visible when viewed from the front)
Cushing’s Syndrome
Typical patient with Cushing’s syndrome.
Note truncal obesity, thinner extremities,
buffalo hump, moon face, and striae
Pancreas
Located in the abdomen Both an exocrine gland (involved in
digestion) and an endocrine gland Secretes insulin and glucagon (PIG) to
control blood glucose levels Islets of Langerhans are hormone
secreting cells of the pancreas
Insulin
Released in response to increased blood glucose levels
Helps transport glucose into most cells (liver and brain do not require insulin); facilitated diffusion
Controls carbohydrate, protein and fat metabolism; stimulates glycolysis for energy and helps liver and muscle to store glucose; stimulates building of proteins from amino acids and promotes building of fats from fatty acids
Insulin
Decreases blood glucose levelsTransports glucose from blood into cellsStimulates cells to burn glucose for energy
The only hormone that lowers blood glucose levels!
Diabetes Mellitus
Insulin deficiency Type I, juvenile or IDDM Severe metabolic disturbances Include the three “polys”
PolyuriaPolydipsia Polyphagia
Hyperglycemia Inability of glucose to enter the cellsBody produces additional glucose
(gluconeogenesis) which also cannot be used by the cells
Excess glucose accumulates in the blood
Diabetes Mellitus
Glucosuria or glycosuriaGlucose in the urine
Polyuria Excretion of large volumes of urine, caused by
glucosuria Polydipsia
Excessive thirst caused by polyuria body’s attempt to replace lost volume)
Diabetes Mellitus
Polyphagia Glucose cannot be utilized so the body takes in more
food for fuel
Acidosis Cells cannot burn glucose, so they burn fatty acids
instead; rapid, incomplete breakdown of these results in formation of ketoacids (ketone bodies)
Ketoacidosis Results from accumulation of ketone bodies from fat
breakdown; gives fruity odor to breath; medical emergency
Diabetes Mellitus
Type II diabetes, adult onset diabetes or NIDDM
May have excessive amounts of insulin (hyperinsulinemia), but it cannot function effectively (resulting in hyperglycemia)
Diabetes Mellitus
Damaged insulin receptorsCannot respond to insulin, resulting in
hyperglycemia (which triggers more insulin to be released)
Diminished number of receptorsNumber of receptors can change; lack of
exercise and obesity can decrease number Excess adipose tissue
Secrete hormones that cause a state of insulin resistance
Diabetes Mellitus
Glucagon
Secreted by the pancreas Stimulated by low blood glucose levels Raises blood glucose levels
Converts glycogen stored in the liver into glucose
Stimulates gluconeogenesis
In practice… Diabetic patients are prone to infections Infection increases glucagon secretion, along
with stress hormone secretion (cortisol, epinepherine, growth hormone)
All of these elevate blood glucose levels Patients receiving steroids for other problems
(like prednisone) will also have elevated glucose levels (prednisone mimics cortisol)
So if your diabetic patient has an infection or is on long term steroid therapy- expect them to require higher than normal doses of insulin
NCLEX Question
After several diagnostic tests, a client is diagnosed with diabetes insipidus. The nurse understands that which symptom is indicative of this disorder?
1. diarrhea2. polydipsia3. weight gain4. blurred vision
Rationale
2. Polydipsia, increased thirst, is a common symptom of diabetes insipidus. The patient experiences increased thirst because of the increased fluid loss.
NCLEX Question
Which clinical manifestation should the nurse expect to note when assessing a client with Addison’s disease?
1. Edema
2. Obesity
3. Hirsutism
4. Hypotension
Rationale
4. Hypotension (especially postural) may result from loss of fluids
NCLEX Question
The hypothalamus responds to a decrease in blood pressure by secreting which substance?
1. angiotensin
2. antidiuretic hormone
3. epinepherine
4. renin
Rationale
2. Antidiuretic hormone (ADH)is released in response to declining blood pressure. ADH causes the kidneys to retain water, which increases blood volume and therefore raises blood pressure
NCLEX Question
After a client is admitted with an adrenal malfunction, the nurse demonstrates understanding of the function of the adrenal gland by identifying which hormones as being released by the adrenal medulla?
1. epinepherine and norepinepherine2. glucocorticoids, mineralocorticoids, and androgens3. thryroxinen(T4), triiodothyronine (T3) and calcitonin 4. insulin, glucagon and somatostatin
Rationale
Epinepherine and norepinepherine are both released from the adrenal medulla.
NCLEX Question
Diabetes insipidus is a disorder of which gland?
1. adrenal gland
2. parathyroid gland
3. pituitary gland
4. thryoid gland
Rationale
Diabetes insipidus occurs as a result of the absence of ADH. ADH is secreted by the posterior pituitary gland
NCLEX Question
Which disease is caused by a deficiency of cortical hormones?
1. Addison’s disease
2. Cushing’s syndrome
3. diabetes mellitus
4. diabetic ketoacidosis
Rationale
Addison’s disease results from a lack of cortical hormones