Transcript Thyroid Powerpoint (GOOD COPY)

Basic Anatomy
The thyroid gland is
located in the lower part
of the neck and is
partially wrapped
around the trachea
(windpipe). It has two
lobes that are joined
together in the middle,
giving it a shape similar
to a butterfly.
Posterior (Back) View
of Thyroid Gland
The four parathyroid
glands are located in the
back of the thyroid
gland. They are roughly
the size of a pea and
yellow in color.
The Thyroid Gland
The thyroid gland regulates the body’s metabolism by
adjusting the rate at which glucose is oxidized (through
cellular respiration).
The main function of the thyroid gland is to produce
hormones. These hormones regulate how much energy the
body expends (called metabolism).
The Thyroid Gland and Homeostasis
The thyroid gland secretes two hormones that help control
metabolism. They are called Thyroxine (T4) and
Triiodothyronine (T3). Iodine is an essential component of
both T3 and T4.
Thyroxine (T4) is secreted by the thyroid gland. It is the
inactive form of Triiodothyronine (T3). It is easily converted
by body cells into T3 by removing one of its four iodine
molecules.
Triiodothyronine (T3) raises metabolism by stimulating
increased sugar utilization by cells. T3 is 8 times more
effective than T4 at increasing metabolism.
Iodine
T4 - Thyroxine
T3 -Triiodothyroxinine
The Parathyroid Glands and Homeostasis
The parathyroid glands help regulate calcium levels in the blood and lower
phosphate levels. Calcium is used by the body for development and
maintenance of strong bones and teeth. It is also helps the heart, nerves,
muscles and other body systems to work properly.
When the level of calcium in the blood is too low, the parathyroid glands
release parathyroid hormone (PTH). A rise in PTH causes calcium levels in
the blood to increase and phosphate levels to decrease. This hormone
increases the level of calcium by influencing the kidneys, intestines, and
bones.
PTH causes the kidneys to reabsorb more calcium, so less calcium is
excreted in the urine. The intestines absorb and retain more calcium from
undigested foods. Calcium is released from bones where it is stored.
(98% of calcium is stored in the skeletal system.)
Kidneys reabsorb Ca2+
Intestines absorb Ca2+
Bones release Ca2+
When bone cells break down, calcium is separated from phosphate ions.
The calcium is reabsorbed into the blood and the phosphate ions are
excreted in the urine. Calcium levels in the blood return to normal, so
PTH secretion stops.
http://www.nlm.nih.gov/medlineplus/tutorials/thyroidsurgery/htm/_no_50_no_0.htm
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Parathyroid Hormone Feedback Loop
1. Low Ca2+ levels in the blood cause the parathyroid glands to release
parathyroid hormone (PTH).
2. The kidneys reabsorb more calcium, the intestines absorb and retain
calcium from food, and calcium is released from bones.
3. These 3 factors cause Ca2+ levels in the blood to rise.
4. Calcium levels are back to normal so PTH secretion stops.
Important Hormones
Hormone
Secreted by…
Target Area(s)
Effect
Thyroxine (T4) &
Triiodothronine
(T3)
Thyroid
All body cells
Controls
metabolism
Thyroid
Bone cells
Lowers the level of
calcium in the
blood
Parathyroid
Kidneys
Intestines
Bones
Raises calcium
levels in the blood
Calcitonin
Parathyroid
Hormone (PTH)
We already know about feedback loops
in Homeostasis…
Monitors/
Receptors
Effectors/
Regulators
Control
System
Negative Feedback Loop for the Thyroid Gland

Hypothalamus
(senses decreased
metabolism)
 Thyroid –
releasing
hormone
(TRH)

Pituitary


Metabolism is back to
normal, hormone
secretion slows down

T3 and T4

Thyroid
Thyroid
Stimulating
Hormone
(TSH)
T3 and T4 Feedback Loop
Legend
TRH = Thyroid
Releasing Hormone
TSH = Thyroid
Stimulating Hormone
T3 = Triiodothyronine
T4 = Thyroxine
Goiters
A goiter is a pronounced
swelling of the thyroid
gland in the neck caused
by insufficient iodine
intake in the diet.
The main source of iodine
in your diet is iodized salt.
Thyroid Disorders
Hypothyroidism
(“Hypo” means less)
Hyperthyroidism
(“Hyper” means more)
Underactive Thyroid Gland
Overactive Thyroid Gland
Occurs when the thyroid
doesn’t produce enough
hormones.
Occurs when the thyroid
produces excess hormones.
Hypothyroidism decreases
metabolism.
Hyperthyroidism increases
metabolism.
Hypothyroidism
• fatigue
• feeling cold
• weight gain
• depression
• reduced concentration
• swollen face
• dry skin
• dry & brittle hair and nails
• constipation
• goiter
Hyperthyroidism
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fatigue
feeling hot
weight loss
increased appetite
nervousness and anxiety
increased heart rate
increased blood pressure
shaking hands
frequent bowel movements
bulging eyes
hair loss
Treatment
Hypothyroidism: most patients take
hormone replacement pills (i.e. eltroxin)
to bring their thyroid hormone levels back
up to normal.
Hyperthyroidism: patients are treated with drugs that bind to
iodine to partially block the production of hormones, bringing
hormone levels back down to normal. However, if medication
isn’t working radioactive iodine can be used to destroy the
hyperactive thyroid tissue. This can sometimes affect the entire
thyroid gland leading to hypothyroidism.
Sometimes surgery is required to remove tumors or cysts that
could cause either hypothyroidism or hyperthyroidism.
http://video.about.com/thyroid/Thyroid-Disease.htm
QUIZ
1.
True or False?
A parathyroid gland is larger than
a thyroid gland.
FALSE
2.
How many parathyroid glands does a
typical person have?
A)
B)
C)
D)
One
Two
Four
Six
Answer: C
3.
True or False?
The thyroid gland plays an important part in
controlling metabolism.
TRUE
4.
What is hypothyroidism?
A) The thyroid gland is incapable of making
hormones.
B) The thyroid gland produces too many
hormones.
C) The thyroid gland produces not enough
hormones.
D) The parathyroid glands are cancerous.
Answer: C
5.
True or False?
Hyperthyroidism causes the body cells to
burn more energy than normal, decreasing
metabolism.
FALSE
6. What causes a goiter?
A)
B)
C)
D)
Hypoparathyroidism
Hyperparathyroidism
An insufficient amount of iodine in your diet
A genetic mutation
Answer:
C
7. You are a doctor. A patient has
inexplicably lost a lot of weight, despite
having an increased appetite. They have an
increased heart rate and high blood
pressure as well. They also feel very tired,
and have bulging eyes.
What would you diagnose them with?
Hyperthyroidism