foreign
toxic multinodular goiter also called
plumber's disease toxic refers to
something harmful nodular refers to
little lumps or nodules of tissue and
goiter refers to a large thyroid gland
so toxic multi-nodular goiter is a
condition where the thyroid gland
enlarges and is filled with lots of
little nodules of tissue Each of which
produces so much thyroid hormone that it
becomes harmful to the body
now normally the hypothalamus which is
located at the base of the brain detects
low blood levels of thyroid hormones and
releases thyrotropin releasing hormone
into the hypophyseal portal system
which is a network of capillaries
linking the hypothalamus to the anterior
pituitary
the anterior pituitary then releases
thyroid stimulating hormone also called
thyrotropin or just TSH
stimulates the thyroid gland
which is a gland in the neck that looks
like two thumbs hooked together in the
shape of a v
the thyroid gland is made up of
thousands of follicles which are small
spheres lined with follicular cells
follicular cells convert thyroglobulin
which is a protein found in follicles
into two iodine-containing hormones try
iodothyronine or T3
and thyroxine or T4
once released from the thyroid gland
these hormones enter the blood and bind
to circulating plasma proteins
only a small amount of T3 and T4 will
travel Unbound in the blood and these
two hormones get picked up by nearly
every cell in the body
once inside the cell T4 is mostly
converted to T3 at which point it can
exert its effect
T3 speeds up the basal metabolic rate so
as an example they might produce more
proteins and burn up more energy in the
form of sugars and fats
it's like the cells are in kind of a
frenzy
T3 also increases cardiac output
stimulates bone resorption which thins
out the bones and activates the
sympathetic nervous system which is the
part of the nervous system that's
responsible for our fight-or-flight
response
that being said thyroid hormone is
important and the occasional increase is
kind of like getting a boost to fight
off a hungry predator or to stay warm
during a snowstorm
toxic multi-nodular goiter usually
starts with a chronic lack of dietary
iodine and follicular cells need iodine
to make P3 and T4
with less iodine around each follicular
cell makes less thyroid hormone and as a
whole the level of thyroid hormone goes
down
in response to low levels of thyroid
hormones the anterior pituitary releases
TSH
the high levels of TSH cause thyroid
hypertrophy which is the buildup in
thyroid tissue and hyperplasia which
increases the number of follicular cells
some parts of the thyroid gland are more
responsive to TSH than others so the
growth ends up being uneven throughout
the thyroid
those responsive follicular cells start
to grow quickly and develop into a
nodule
and the rest of the gland ends up
looking basically the same
typically multinodular goiter starts
with a single nodule and then over the
years multiple nodules start to appear
this strategy works for a while and the
thyroid is considered a non-toxic
multinodular goiter
in other words having more follicular
cells makes up for the fact that each
follicular cell makes less thyroid
hormone
so the thyroid enters a balanced or EU
thyroid state
at this point the TSH levels go down
even though there's an iodine deficiency
but if that iodine deficiency worsens
there's another round of increased TSH
which stimulates more thyroid growth
over time the thyroid gland goes through
a ton of cycles of periods of growth and
periods of balance
now a non-toxic multinodular goiter
becomes toxic when a genetic mutation
happens in one of the dividing
follicular cells
in particular when the mutation affects
the TSH receptor
if the mutation causes the TSH receptor
to be constantly on then the affected
cell might constantly remains stimulated
to divide and produce thyroid hormone
at this point it develops into a toxic
nodular goiter
even when thyroid hormone levels rise in
TSH Productions shut down these
independent nodules use any available
iodine to make thyroid hormone well
beyond what the body wants or needs
the result is that cells across the body
are in a state of hyper metabolism where
cellular reactions are constantly
happening at a faster Pace than normal
symptoms of toxic multi-natural goiter
are related to the enlargement of the
thyroid gland and a hyperthyroidism
the enlarged thyroid gland can put
pressure on other structures in the neck
obstructing the airway and making
swallowing difficult
it can also compress nerves like the
Superior or recurrent laryngeal nerves
which will make the voice sound hoarse
it can cause superior vena cava syndrome
by limiting blood flow in the superior
vena cava which results in facial and
arm swelling because blood gets backed
up in the veins of the head and upper
body
hyperthyroidism causes weight loss
despite an increase in appetite because
of the higher basal metabolic rate as
well as heat intolerance because the
body is producing more heat and rapid
heart rate sweating hyperactivity
anxiety and insomnia because of the
effect of thyroid hormones and the
sympathetic nervous system
pathetic overstimulation of muscles that
control eye movements also makes the
eyes appear more open than normal
so you see more of the white of the eyes
thyroid storm which is a
life-threatening complication of
hyperthyroidism where the body goes into
a state of severe hyper metabolism can
develop when someone with
hyperthyroidism stops their treatment
develops an infection or has surgery
all the normal symptoms of
hyperthyroidism become exaggerated for
example heat intolerance turns to high
fever and rapid heart rate turns to
cardiac arrhythmia
diagnosing toxic multinodular goiter
involves confirming hyperthyroidism by
measuring blood levels of TSH T3 and T4
and confirming the presence of
multinodular goiter through
ultrasonography
a radio iodine uptake test can also help
identify independent nodules
the treatment for toxic multinational
goiter is usually done with beta
blockers and surgery can be used to
remove part or all of the thyroid gland
another option radio iodine therapy
involves taking oral doses of
radioactive iodine which is absorbed by
active follicular cells and over time
damages them
this destroys hyper-functioning nodules
within the thyroid gland because radio
iodine gets preferentially picked up by
those nodules leaving the rest of the
gland intact
the long-term use of thioamides which
are anti-thyroid drugs which block
thyroid hormone production and secretion
is typically only used when radio iodine
therapy and surgery aren't appropriate
options
all right as a quick recap toxic
multi-nodular goiter is a condition
where the thyroid gland develops
independently functioning nodules which
results in hyperthyroidism
it develops after prolonged iodine
deficiency which causes hypertrophy and
hyperplasia of the thyroid gland
continued follicular cell division can
lead to a genetic mutation of the TSH
receptor which turns a non-toxic
multinodular goiter into a toxic
multinational goiter
symptoms include an enlarged thyroid as
well as the typical symptoms of
hyperthyroidism like weight loss a rapid
heart rate and hyperactivity
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