Transcript Thyroid imbalances

Thyroid Hormones
and their control
Thyroid hormones control your
metabolic rate. But what controls
your thyroid hormone levels?
In this thyroid tutorial, you should
learn to:
– Explain how thyroid activity is regulated
– Predict and explain hormone levels in different
thyroid imbalances
– Predict and explain signs and symptoms of hyperand hypo-thyroidism
– Identify the emergency complications of hyperand hypo-thyroidism.
– To start, just click the forward arrow. To return to
this menu at any time, click the home button.
Hypothalamus detects low
thyroid hormones
Hypothalamus releases TRH
What’s the next step?
Thyroid secretes
T3 and T4
Hypothalamus
secretes TSH
(thyroid
stimulating
hormone)
Hypothalamus
secretes TRH
(thyrotropin
releasing
hormone)
Good work!
The hypothalamus secretes RELEASING hormones.
In this case, the hypothalamus is trying to stimulate
the thyroid – so it secretes Thyrotropin releasing
hormone.
Thyrotropin means ‘thyroid growth-causer.’ So TRH
is going to tell some other organ to RELEASE a
THYROID GROWTH-CAUSER.
Click on the forward arrow to go on.
Hypothalamus detects low
thyroid hormones
Hypothalamus releases TRH
TRH travels to anterior
pituitary
What’s the next step?
TRH travels to
anterior
pituitary
Hypothalamus
secretes TSH
(thyroid
stimulating
hormone)
Hypothalamus
secretes T3 and
T4
Good work!
The hypothalamus secretes RELEASING hormones.
to tell some other organ to RELEASE a THYROID
GROWTH-CAUSER.
The organ that releases stimulating hormones for
the hypothalamus is the anterior pituitary - just
about an inch below it. The TRH travels from the
hypothalamus to the pituitary through a tiny portal
system of blood vessels.
Hypothalamus detects low
thyroid hormones
Hypothalamus releases TRH
TRH travels to anterior
pituitary
What’s the next step?
anterior
pituitary
releases TSH
(thyroid
stimulating
hormone)
pituitary
Thyroid secretes
secretes T3 & T4
T3 and T4
anterior pituitary releases
TSH
Good work!
When it receives the Thyrotropin Releasing
hormone, the anterior pituitary releases a
thyrotropin, or thyroid stimulating hormone.
Hypothalamus detects low
thyroid hormones
Hypothalamus releases TRH
What’s the next step?
pituitary
secretes T3 & T4
Thyroid
stimulated by
TSH
Thyroid
stimulated by
TRH
TRH travels to anterior
pituitary
anterior pituitary releases
TSH
Good work!
Thyroid stimulated by TSH
Thyroid stimulating hormone does just what its
name says – stimulate the thyroid.
Hypothalamus detects low
thyroid hormones
Hypothalamus releases TRH
What’s the next step?
Thyroid
produces only
T3
Thyroid
produces T3 &
T4
Thyroid
produces TRH
TRH travels to anterior
pituitary
anterior pituitary releases
TSH
Good work!
The thyroid produces 2 hormones.
Thyroid stimulated by TSH
T3 is tri-iodothyronine – 3 iodine atoms
T4 is tetra-iodothyronine – 4 iodine atoms
Thyroid produces
T3 & T4
T3 is the active form. T4 is an inactive backup form;
your tissues can convert it into T3 by taking off an
iodine atom.
Hypothalamus detects low
thyroid hormones
Hypothalamus releases TRH
TRH travels to anterior
pituitary
anterior pituitary releases
TSH
What’s the next step?
Thyroid
measures T3 &
T4, stops
making them
when there is
enough
Hypothalamus
and pituitary
detect T3 & T4;
secrete more
TRH and TSH.
Hypothalamus
and pituitary
detect T3 & T4;
stop secreting
TRH and TSH.
Good work!
Thyroid stimulated by TSH
When T3 & T4 levels return to normal, the
hypothalamus and pituitary no longer need to
stimulate the thyroid.
Thyroid produces
T3 & T4
That is, T3 & T4 exert negative feedback on the
hypothalamus and pituitary.
Hypothalamus and pituitary
detect T3 & T4; stop
secreting TRH and TSH.
Hypothalamus detects low
thyroid hormones
Hypothalamus releases TRH
TRH travels to anterior
pituitary
anterior pituitary releases
TSH
Thyroid stimulated by TSH
Thyroid produces
T3 & T4
Hypothalamus and pituitary
detect T3 & T4; stop
secreting TRH and TSH.
The thyroid is the PRIMARY organ
making the thyroid hormones.
Hypothalamus detects low
thyroid hormones
Hypothalamus releases TRH
TRH travels to anterior
pituitary
anterior pituitary releases
TSH
The anterior pituitary is the
SECONDARY organ responsible for
making thyroid hormones.
Thyroid stimulated by TSH
The thyroid is the PRIMARY organ
making the thyroid hormones.
Thyroid produces
T3 & T4
Hypothalamus and pituitary
detect T3 & T4; stop
secreting TRH and TSH.
Hypothalamus detects low
thyroid hormones
Hypothalamus releases TRH
The hypothalamus is the TERTIARY
organ responsible for making thyroid
hormones.
TRH travels to anterior
pituitary
anterior pituitary releases
TSH
The anterior pituitary is the
SECONDARY organ responsible for
making thyroid hormones.
Thyroid stimulated by TSH
The thyroid is the PRIMARY organ
making the thyroid hormones.
Thyroid produces
T3 & T4
Hypothalamus and pituitary
detect T3 & T4; stop
secreting TRH and TSH.
Hypothalamus detects low
thyroid hormones
A man has high T3 & T4 levels, because of a problem
with his thyroid. What’s his diagnosis?
Hypothalamus releases TRH
Tertiary
Secondary
Primary
hyperthyroidism hypothyroidism hyperthyroidism
TRH travels to anterior
pituitary
anterior pituitary releases
TSH
Thyroid stimulated by TSH
Thyroid produces
Excess T3 & T4
Hypothalamus and pituitary
detect T3 & T4; stop
secreting TRH and TSH.
Good work!
It’s called hyperthyroidism because there is too
much T3 & T4.
It’s called primary because the problem is in the
primary organ making T3 & T4 – the thyroid itself.
Hypothalamus detects low
thyroid hormones
A man has high T3 & T4 levels, because of a problem
with his anterior pituitary. What’s his diagnosis?
Hypothalamus releases TRH
Tertiary
Secondary
Secondary
hyperthyroidism hyperthyroidism hypothyroidism
TRH travels to anterior
pituitary
anterior pituitary releases
Excess TSH
Thyroid overstimulated by
excess TSH
Thyroid produces
Excess T3 & T4
Hypothalamus and pituitary
detect T3 & T4; stop
secreting TRH and TSH.
Good work!
It’s called hyperthyroidism because there is too
much T3 & T4.
It’s called secondary because the problem is in the
secondary organ stimulating T3 & T4 production –
the anterior pituitary.
Hypothalamus detects low
thyroid hormones
A man has primary hyperthyroidism. What will his
levels of TSH be like?
Hypothalamus releases TRH
Normal
High
Low
TRH travels to anterior
pituitary
anterior pituitary releases
TSH
Thyroid stimulated by TSH
Thyroid produces
Excess T3 & T4
Hypothalamus and pituitary
detect T3 & T4; stop
secreting TRH and TSH.
Good work!
With primary hyperthyroidism, this man has too
much T3 & T4 because of a problem with his
thyroid.
The hypothalamus and anterior pituitary are still
working. They will detect these high levels of T3 &
T4, and stop secreting TRH and TSH. Therefore, the
levels of TRH and TSH will be lower than normal.
Hypothalamus detects low
thyroid hormones
A man has secondary hyperthyroidism. What will his
TSH levels be like?
Hypothalamus releases TRH
Low
Normal
High
TRH travels to anterior
pituitary
anterior pituitary releases
TSH
Thyroid stimulated by TSH
Thyroid produces
T3 & T4
Hypothalamus and pituitary
detect T3 & T4; stop
secreting TRH and TSH.
Good work!
In secondary hyperthyroidism, the T3 & T4 levels are
elevated because the anterior pituitary is producing
too much TSH, over-stimulating the thyroid.
TSH levels are higher than normal.
Hypothalamus detects low
thyroid hormones
A man has secondary hyperthyroidism. What will his
TRH levels be like?
Hypothalamus releases TRH
Normal
Low
High
TRH travels to anterior
pituitary
anterior pituitary releases
TSH
Good work!
Thyroid stimulated by TSH
In secondary hyperthyroidism, the T3 & T4 levels are
elevated because the anterior pituitary is producing
too much TSH, over-stimulating the thyroid.
Thyroid produces
T3 & T4
But there is nothing wrong with the hypothalamus,
so it will still detect the high T3 & T4 levels, and stop
producing TRH. TRH levels will be low.
Hypothalamus and pituitary
detect T3 & T4; stop
secreting TRH and TSH.
Hypothalamus detects low
thyroid hormones
A man has tertiary hypothyroidism. What will his
TRH levels be like?
Hypothalamus releases TRH
Normal
Low
High
TRH travels to anterior
pituitary
anterior pituitary releases
TSH
Good work!
Thyroid stimulated by TSH
Hypothyroidism means the thyroid hormone levels
are low.
Thyroid produces
T3 & T4
Tertiary means the organ at fault is the
hypothalamus. It isn’t creating enough TRH to
stimulate the thyroid.
Hypothalamus and pituitary
detect T3 & T4; stop
secreting TRH and TSH.
Hypothalamus detects low
thyroid hormones
A man has low T3 & T4 levels, but high TSH levels.
What’s his diagnosis?
Hypothalamus releases TRH
Tertiary
Secondary
Primary
hypothyroidism hyperthyroidism hypothyroidism
TRH travels to anterior
pituitary
anterior pituitary releases
TSH
Thyroid stimulated by TSH
Thyroid produces
T3 & T4
Hypothalamus and pituitary
detect T3 & T4; stop
secreting TRH and TSH.
Good work!
It’s called hypothyroidism because there is too little
T3 & T4.
you can tell it’s primary because the pituitary is
doing its job – making TSH to stimulate the thyroid.
But the thyroid isn’t responding! The problem must
be with the thyroid itself.
Hypothalamus detects low
thyroid hormones
A man has low T3 & T4 levels, and low TSH levels.
When he is given an injection of TRH, his T3 & T4 go
back to normal. What’s his diagnosis?
Hypothalamus releases TRH
TRH travels to anterior
pituitary
Tertiary
Secondary
Tertiary
hypothyroidism hypothyroidism hyperthyroidism
anterior pituitary releases
TSH
Good work!
Thyroid stimulated by TSH
It’s called hypothyroidism because there is too little
T3 & T4.
Thyroid produces
T3 & T4
you can tell it’s tertiary - involving failure of the
hypothalamus - because when you give him the
hormone the hypothalamus should be making, you
fix his problem.
Hypothalamus and pituitary
detect T3 & T4; stop
secreting TRH and TSH.
Hypothalamus detects low
thyroid hormones
In Grave’s disease, antibodies shaped like TSH attach
to TSH receptors on the thyroid and cause it to make
excess T3 & T4. What kind of imbalance results?
Hypothalamus releases TRH
TRH travels to anterior
pituitary
Primary
Secondary
Tertiary
hyperthyroidism hyperthyroidism hyperthyroidism
anterior pituitary releases
TSH
Good work!
Thyroid stimulated by TSH
Thyroid produces
T3 & T4
Hypothalamus and pituitary
detect T3 & T4; stop
secreting TRH and TSH.
It’s called hyperthyroidism because there is too
much T3 & T4.
It’s called primary because there’s nothing wrong
with the pituitary or the hypothalamus. They are
just doing their jobs as usual.
Hypothyroid: low thyroid
hormones
What is most likely to happen to someone who is
hypothyroid?
Decreased aerobic
metabolism
Decreased temperature
Decreased
temperature
Elevated WBC
count
Hypertension
Good work!
Your body is warm because heat is produced as a
byproduct of aerobic metabolism. If you are doing
less aerobic metabolism, your temperature will
decrease.
Hypothyroid: low thyroid
hormones
What is most likely to happen to someone who is
hypothyroid?
Decreased aerobic
metabolism
Decreased temperature
Fatty stools
Weight loss
Weight gain
Weight gain
Good work!
When metabolic rate decreases, less food is burned
to make ATP. The unused food is stored in the body
– leading to weight gain.
Hypothyroid: low thyroid
hormones
What is most likely to happen to someone who is
hypothyroid?
Decreased aerobic
metabolism
Decreased temperature
Fast reflexes
Diarrhea
Constipation
Weight gain
Constipation
Good work!
When metabolic rate decreases, muscles are less
active. Bowel movement decreases.
Hypothyroid: low thyroid
hormones
What is most likely to happen to someone who is
hypothyroid?
Decreased aerobic
metabolism
Decreased temperature
Strong
heartbeat
Wide pulse
pressure
Weak heartbeat
Weight gain
Constipation
Weak heartbeat
Good work!
When metabolic rate decreases, muscles are less
active. Heart movement decreases, weakening the
heartbeat.
Hypothyroid: low thyroid
hormones
Decreased aerobic
metabolism
Hypothyroidism also causes a condition called
myxedema, or mucusy edema.
Decreased temperature
In myxedema, mucus builds up under the skin,
giving it a dry, puffy look.
Weight gain
Constipation
Weak heartbeat
Dry, puffy skin
Enlarged tongue
Croaking voice
The myxedema may also affect the tongue, making
it larger. The vocal cords may swell, making the voice
croaky.
Hypothyroid: low thyroid
hormones
Decreased aerobic
metabolism
Which of the signs and symptoms listed is most
likely to cause a severe complication? Click on the
one that worries you most.
Decreased temperature
Weight gain
Constipation
Weak heartbeat
Dry, puffy skin
Enlarged tongue
Croaking voice
Good work!
When metabolic rate decreases, muscles are less
active. Heart movement decreases, weakening the
heartbeat.
If somebody with hypothyroidism catches an
additional illness, their condition may get worse.
Their heart might slow so much that it causes
vascular collapse. This is called myxedema coma.
Hyperthyroid: high thyroid
hormones
What is most likely to happen to someone who is
hyperthyroid?
Increased aerobic
metabolism
Increased appetite
Increased
appetite
Elevated WBC
count
Decreased
temperature
Good work!
A person with a high metabolism is always hungry –
the food is being burned up to make ATP as fast as
the person can eat it!
Hyperthyroid: high thyroid
hormones
What is most likely to happen to someone who is
hyperthyroid?
Increased aerobic
metabolism
Increased appetite
Fatty stools
Weight gain
Weight loss
Weight loss
Good work!
When metabolic rate increases, more food is burned
to make ATP.
Hyperthyroid: high thyroid
hormones
What is most likely to happen to someone who is
hyperthyroid?
Increased aerobic
metabolism
Increased appetite
Constipation
Sweating
Decreased
temperature
Weight loss
Sweating
Good work!
When metabolic rate increases, more food is burned
to make ATP. This produces more heat, which
means the person will be overheated and sweating.
Hyperthyroid: high thyroid
hormones
What is most likely to happen to someone who is
hyperthyroid?
Increased aerobic
metabolism
Increased appetite
Lethargy
Tremor
Hypotension
Weight loss
Sweating
Tremor
Good work!
When metabolic rate increases, muscles and nerves
make more ATP and are more active. This can
present as tremor and anxiety.
Hyperthyroid: high thyroid
hormones
What is most likely to happen to someone who is
hyperthyroid?
Increased aerobic
metabolism
Increased appetite
Somnolence
Anorexia
Tachycardia
Weight loss
Sweating
Tremor
Tachycardia
Good work!
When metabolic rate increases, cardiac muscles
make more ATP and are more active. This can
present as tachycardia, a strong pulse, and a
widened pulse pressure.
Hyperthyroid: high thyroid
hormones
Increased aerobic
metabolism
Which of the signs and symptoms listed is most
likely to cause a severe complication? Click on the
one that worries you most.
Increased appetite
Weight loss
Good work!
Sweating
If somebody with hyperthyroidism catches an
additional illness, their condition may get worse.
Their heart might speed up so much that there isn’t
time for it to fill between beats. This causes vascular
collapse. At the same time, their fever might soar to
dangerous levels.
This is called thyroid storm.
Tremor
Tachycardia
Exophthalmos
This is the end of the thyroid tutorial.
• You should be able to:
– Explain how thyroid activity is regulated
– Predict and explain hormone levels in different
thyroid imbalances
– Predict and explain signs and symptoms of hyperand hypo-thyroidism
– Identify the emergency complications of hyperand hypo-thyroidism.
• Not sure? Just click on the topic you want to
review.