Download The Endocrine System/Part II - Wilkes

The Endocrine System/Part II
Joe Pistack MS/ED
Thyroid Gland
• Largest of the endocrine
glands.
• Situated on the front
sides of the trachea.
• Butterfly-shaped, has
two lobes connected by
a tissue band called the
isthmus.
Thyroid Gland
• Thyroid gland contains
two types of cells:
• Follicular cells-located
within the thyroid follicle.
Secrete T3 and T4
(discussed later)
• Parafollicular cells-located
between the follicles.
• Each type of cells secrete
a particular hormone.
Thyroid Gland
• Composed of secretory units called follicles.
• Each follicle is filled with a clear, viscous
substance called colloid.
• Follicular cells secrete two thyroid hormones:
• (1) triiodothyronine (T3)
• (2) tetraiodothyronine (T4 or thyroxine)
Thyroid Gland
• Functions of T3 and T4:
• Regulate all phases of metabolism and are
necessary for the proper functioning of all
other hormones.
• Thyroid hormones are necessary for the
normal maturation of the nervous system and
for normal growth and development.
Hypothyroidism
• Adult-results in a condition called Myxedema.
• Myxedema-slowed metabolic state.
• Skin becomes thick and puffy due to
accumulation of a thick fluid under the skin.
Hypothyroidism
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Signs/Symptoms:
Slow heart rate
Sluggish peristalsis
Constipation
Low body temperature
Low energy
Loss of hair
Weight gain
Hypothyroidism
• Cretinism-infant born
with no thyroid gland.
• Fails to develop both
physically and mentally.
• Child will be short and
stocky with abnormal
skeletal development
and severe mental
retardation.
Hyperthyroidism
• Hyperthyroidism-caused by an excess of
thyroid hormone.
• Metabolic state is “sped-up”.
• At risk for developing fast rhythm disorders of
the heart.
Hyperthyroidism
• Grave’s disease-common type of
hyperthyroidism.
• Signs/Symptoms:
• Increased heart rate
• Increased peristalsis/diarrhea
• Elevation in body temperature
• Hyperactivity
• Weight loss
• Emotional swings
Hyperthyroidism
• Grave’s disease is also
characterized by
bulging eyes
(exophthalmia).
• Bulging of eyes is
caused by fat pads
behind the eyeballs
pushing the eyeballs
forward in the eye
socket.
Iodine
• Synthesis of T3 and T4 requires iodine.
• Iodine in the body comes from dietary
sources.
• Most of the iodine in the blood is pumped
into the follicular cells of the thyroid
hormones where it is used in the synthesis of
thyroid hormones.
Iodine Deficiency
• Iodine deficient state –T3 and T4 production
decreases because iodine is necessary for the
synthesis of the thyroid hormones.
• With insufficient iodine, negative feedback is
not possible.
• Persistent stimulation of the thyroid gland by
TSH causes thyroid to enlarge.
Iodine Deficiency
• Enlarged Thyroid gland
is called a goiter.
Diagnosis is usually
made by ultrasound.
Calcitonin
• Calcitonin-secreted by the parafollicular cells
of the thyroid gland.
• Calcitonin helps regulate blood levels of
calcium.
Parathyroid Glands
• Four tiny glands that lie
along the posterior
surface of the thyroid
gland.
• Secretes parathyroid
hormone (PTH).
Parathyroid Glands
• Low blood level of calcium stimulates the
release of PTH.
• PTH has three target organs:
– Bone
– Digestive tract
– Kidneys
• Overall effect of PTH is to increase calcium
levels.
Parathyroid Gland
• Hypocalcemia-low calcium levels.
• Calcium deficiency results in continuous
muscle contraction known as tetany.
• Contorts the wrist , can cause sustained
contraction of the muscles of the larynx
(laryngospasm).
Hypercalcemia
• Increased calcium level.
• PTH stimulates osteoclastic activity in the
bones, moves calcium out of the bone causing
hypocalcemia.
• Hypercalcemia depresses the nervous, cardiac
and GI systems causing fatigue, bradycardia,
anorexia and constipation.
Adrenal Glands
• small glands
located above the
kidneys.
• Consists of two
regions:
• Inner medulla
• Outer cortex
Adrenal Medulla
• Inner region of the adrenal gland, considered
an extension of the sympathetic nervous
system “fight or flight”.
• Catecholamines- Hormones that are secreted
in emergency situations. They are:
– Epinephrin (adrenaline)
– Norepinephrine
Adrenal Medulla
• Catecholamines help the body respond to
stress by:
• Elevating blood pressure.
• Increasing heart rate.
• Convert glycogen to glucose in the liver, more
glucose available to the cells.
• Increases metabolic rate, making more energy.
• Opens up the bronchial passages.
Adrenal Cortex
• Outer region of the
adrenal gland.
• Secretes hormones
called steroids.
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Three steroidsGlucocorticoids
Mineralcorticoids
Sex hormones
Adrenal Cortex
• Adrenal cortical hormones are essential for
life.
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Adrenal cortical hormones regulate:
Glucocorticoids
sugar
Mineralcorticoids salt
Sex hormones
sex
Adrenal Cortex
• Glucocorticoids-convert amino acids into
glucose (gluconeogenesis).
• Maintain blood glucose levels between meals.
• Ensures steady supply of glucose for the brain
and other cells.
• Chief glucocorticoid is cortisol.
Adrenal Cortex
• Cortisol is secreted in greater amounts during
stress. (physiological stress, disease, physical
injury, emotional stress).
• Has an anti-inflammatory effect.
• Ex. Cortisol-like drug-prednisone, used in
treatment of arthritis or severe allergic
response.
Adrenal Cortex
• Mineralocorticoids:
• Aldosterone-chief mineralocorticoid.
• Plays a role in the regulation of blood volume
and blood pressure and in the concentration
of electrolytes.
• Called salt retaining hormone.
Adrenal Cortex
• Sex hormones:
• Secreted in small amounts.
• Female hormones-estrogens.
• Male hormones-androgens.
Adrenal Gland
• Adrenal insufficiency is life threatening and
must be treated with steroids and
replacement of fluids and electrolytes.
• Hypersecretion-excess of adrenal cortical
hormones.
• Cushing’s syndrome-elevated blood levels of
steroids, such as prednisone.
Adrenal Cortex
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Cushing’s syndrome s/s:
Truncal obesity.
Rounded facial appearance (moon face).
Excess fat deposition between the shoulders
(buffalo hump).
Facial hair (hirsutism).
Thin skin that bruises easily.
Bone loss .
Muscle weakness.
Cushing’s Syndrome
Adrenal Gland
• Hyposecretion-adrenal gland fails to secrete
adequate amounts of adrenal cortical
hormones.
• Addison’s disease-adrenal insufficiency.
• s/s-generalized weakness, muscle atrophy,
bronzing of the skin, severe loss of fluids and
electrolytes.
Addison’s Disease
The Pancreas
• Long slender organ that lies transversely
across the upper abdomen.
• Functions as an endocrine and exocrine gland.
• Secretes two hormones: insulin and glucagon.
• Islets of Langerhans-hormone-secreting cells
of the pancreas.
The Pancreas
Pancreas
• Islets of Langerhans contain two types of cells:
• Alpha cells-secrete glucagon.
• Beta cells-secrete insulin.
• Both regulate blood sugar.
Pancreas
• Insulin is released in response to increased
blood levels of glucose as occurs following a
meal.
• Secretion of insulin decreases as blood levels
of glucose decrease.
• Insulin has many target tissues, exerts
widespread effects.
Insulin and Blood Glucose
• Insulin decreases blood glucose levels for two
reasons:
– Increases transport of glucose from the blood into
the cells.
– Stimulates the cells to burn glucose as fuel.
• Insulin is the only hormone that lowers blood
glucose.
Pancreas
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Hyperglycemia-excess glucose in the blood.
Signs/symptoms:
Glucosuria-glucose in the urine.
Polyuria-excretion of large volumes of urine.
Polydipsia-excessive thirst.
Polyphagia-excessive eating.
Acidosis-due to the rapid breakdown of fatty
acids.
Pancreas
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Hypoglycemia-low blood sugar.
Signs/symptoms:
Cool, clammy skin
Weakness
Pale
Lethargy
Headache
Shakiness
Gonads
• Sex glands:
• Ovaries in female.
• Testes in male.
• Ovaries secrete : estrogen and progesterone.
– Females appear female because of estrogen
• Testes secrete : testosterone
– Males appear male because of testosterone.
Thymus Gland
• Thymus gland-lies in the thoracic cavity
behind the sternum.
• Larger in child than in an adult, becomes
smaller as child hits puberty.
• Secretes the hormones called thymosins, play
a role in immunity.
Thymus Gland
Pineal Gland
• Cone-shaped gland, located close to the
thalamus in the brain.
• Called the body’s “biological clock” controlling
many biorhythms.
• Secretes a hormone called melatonin.
Pineal Gland
• Plays a role in sexual maturation and the
sleep-wake cycle.
• Melatonin secretion is lowest during the
daylight hours and highest at night.
Pineal Gland
Prostaglandins
• Hormones derived from a fatty acid called
arachidonic acid- a fatty acid found in the
membranes of body cells
• Produced by many tissues.
• Chemical mediators of pain and inflammation,
increase sensitivity of nerve endings to pain
• Aspirin and ibuprofin block synthesis of
prostaglandins-useful in pain control.
As we Age
• Alteration in the secretion of hormones.
• Decrease in the levels of secretion of the
glands.
• Decrease in the level of thyroid hormones and
decreased metabolic rate.
• Decrease in the amount of growth hormone,
decrease in muscle mass and increase in
storage of fat.
• Diminished circadian control.