hey everyone we're talking about vitamin
d toxicity in this lesson so we're going
to talk about some of the causes of
vitamin d toxicity we're also going to
talk about some of the pathophysiology
the signs and symptoms how we can
diagnose it and how we can treat it
so vitamin d toxicity is also known as
hypervitaminosis
d so that's just another name for
vitamin d toxicity
now vitamin d toxicity really what it is
is it is toxic levels of vitamin d so
very very high levels of vitamin d
once you have reached a point where you
saturate
the storage of vitamin d in your body
and
saturate the receptors vitamin d
receptors
you can lead to a toxic state so vitamin
d is actually a fat
soluble vitamin and it's actually mainly
stored in the liver and fat tissue
so those are two areas where vitamin d
is stored
so what are some of the sources of
vitamin d so some of the sources include
exogenous sources so outside the body so
these are dietary sources like animal
food
products so these include fish and meat
we can also get from fortified dairy
milk so a lot of times
dairy milk is fortified with vitamin d
and really what that means is vitamin d
is added to the dairy milk
and that helps us absorb the calcium
from the dairy milk
and then what's important here is i have
it bolded is
we can get it from vitamin d supplements
and this can be one of the major causes
of vitamin d toxicity as we will see
soon
some of the other sources of vitamin d
include endogenous
synthesis so synthesis inside our body
and what happens is the vitamin d is
actually derived from cholesterol
when the cholesterol is exposed to sun
in our skin
so we can actually get vitamin d in that
way as well
and once we have vitamin d vitamin d is
used for several processes we're going
to talk about some of those processes in
the next slide
but because vitamin d is a fat soluble
vitamin it may be more difficult to
actually get rid of
vitamin d as opposed to some
water-soluble vitamins that can be
excreted
from the urinary system and because of
this there are actually some
maximum daily amounts of vitamin d
that are suggested so that we don't take
in too much one of those
is a maximum suggested daily intake of 4
000 international units per day and this
is
from this article here entitled
evaluation treatment and prevention of
vitamin d deficiency
in endocrine society clinical practice
guideline
published in 2011. so this is the
article that actually suggests
this maximum daily intake so what are
some of the causes of vitamin d toxicity
so one of the causes of vitamin d
toxicity is actually ingestion
of very high doses of vitamin d
supplements
so this is actually one of the most
important and most common causes of
vitamin d toxicity we can see
so when we look at the patient's history
we ask them questions you know how much
vitamin d supplements
are you taking they may have other
health issues that require them to take
vitamin d supplements
and because of this they can be taking
too much and a lot of times it may be
due to prescription errors there may be
an issue with the amount that they're
taking they may be taking too much
so that is one important cause of
vitamin d toxicity ingestion of very
high doses of vitamin d
supplements the second is ingestion of
high doses of vitamin d supplements so
not necessarily very high but high
normal
levels of vitamin d supplements but they
also have
very high consumption of fortified milk
so fortify milk again contains
vitamin d and if they're drinking a very
very
large amount of fortified milk in
addition to high doses of vitamin d
supplements even though those
supplements are at the proper
dosage these two combined can lead to
vitamin d toxicity as well
now it's important to point out before i
move on
is that eating fish and meat don't seem
to provide enough
vitamin d to actually lead to vitamin d
toxicity
and the endogenous synthesis of vitamin
d from our skin
does not appear to cause vitamin d
toxicity either so these are often the
two main
culprits the next point is very
important to
recognize and identify and that is that
vitamin d
can actually be excessively produced
from granulomatous conditions
these include sarcoidosis and
tuberculosis
and certain lymphomas can actually
produce high levels of vitamin d as well
so granulomatous conditions like
sarcoidosis and tuberculosis
and certain lymphomas can lead to
vitamin d toxicity as well so it's
important to
think about these conditions too so what
is the pathophysiology of vitamin d
toxicity so really because there's so
much vitamin d
present it leads to an increased
activation of vitamin d pathways
so in our gastrointestinal system
calcitriol which is the
active form of vitamin d leads to the
increased absorption of calcium and
phosphate
it also increases the absorption of
calcium and phosphate from our renal
system as well from our kidneys
so calcitriol does both so it is an
important
mediator of bringing in calcium into our
body
and i have a whole lesson on the pathway
as to
how calcitriol does this if you want
more information please check out my
lesson on vitamin d and calcium but just
briefly
we see here in the gastrointestinal
system
here is an enterocyte here is the
gastrointestinal lumen and here's the
blood vessel
calcium can be brought in through a
calcium transporter
it binds to calbinin and calcitriol
also can enter the cell it is a fat
soluble vitamin so it can cross the
membrane
it binds to vitamin d receptor can also
go in
to the nucleus and activate genetic
programs that lead to
more cowbinding and increased atp
dependent calcium pumps on the
blood vessel side so that induces the
enterocyte to bring in
calcium into the blood so that is a very
simplistic
look at this pathway if you want more
information again please check out my
lesson on that topic
so what are the clinical features of
vitamin d toxicity
well we basically really talked about
what it does it
leads to an increased absorption of
calcium so
really the clinical features of vitamin
d toxicity are
due to hypercalcemia or increased
calcium in the blood
but first it's important to recognize
that even having high levels of vitamin
d and hypercalcemia
an individual may be asymptomatic they
may not be presenting
anything overt so you may not be able to
see this or they may not be complaining
of any
obvious symptoms when they are
symptomatic they are often non-specific
so we'll see all the different symptoms
we can have with hypercalcemia
so we remember the signs and symptoms of
hypercalcemia with the mnemonic
bones stones drones and moans and the
other version is
psychiatric overtones so these are the
categories of
symptoms of hypercalcemia so again
vitamin d toxicity causes hypercalcemia
it's going to cause these symptoms these
following symptoms
so the first one is bones so
this leads to bone aches and pain so we
can see bone aches and pain
in individuals with hypercalcemia the
next category is stones
so with regards to stones these are
nephrolithiasis
so kidney stones this is really what
this is and it can be
calcium oxalate stones and we can also
get calcium deposits in the kidney so
nephrocalcinosis so these are
issues that we can see with
hypercalcemia
now with regards to groans so we've gone
through
bones stones and then we're on to groans
groans
involve muscle aches and pains
we can see muscle weakness we can see
out developing as well with these
individuals
they also have gastrointestinal symptoms
so really groans is encompassing
a lot of pain and weakness with these
patients so gastrointestinal symptoms we
see with hypercalcemia
include abdominal pain nausea and
vomiting constipation
peptic ulcer disease and pancreatitis
because there's
calcium deposits in the pancreas
and then in the last category moans or
psychiatric overtones that might help
you with these next symptoms
these include depression and anxiety
fatigue and lethargy
sleep disturbances confusion or an
altered mental status
apathy irritability and agitation and in
some
severe cases can even lead to coma so
again there's many many different
symptoms
of hypercalcemia so we can see all of
these symptoms and we can see that it
may be non-specific and so it may be
difficult to recognize that some of
these symptoms may be due to
hypercalcemia which is ultimately due to
the vitamin d toxicity
and there are some other clinical
features of vitamin d toxicity as well
these include polydipsia so they can be
drinking a lot have a high
fluid intake they can have polyuria so
high urine output they can be urinating
a lot and because they have high urinary
output they may be dehydrated so they
may have signs of hypovolemia
so these include dry mucous membranes
and skin tinting
and dry axilla those types of signs
they can also have hypertension so high
blood pressure
and they may also have weight loss due
to anorexia
and an also important point to note with
hypercalcemia is that they can have
cardiac arrhythmias
so they can have a shortened qt interval
so you can see here
this qt interval is a lot
less than half of the r to our interval
so that could give you a clue now this
is not necessarily
an ecg of someone with hypercalcemia but
we can see that there is a short
qt interval here they may also have
a flattened t wave and a shortened st
segment as well
so how is vitamin d toxicity diagnosed
and how is it treated
so diagnosis of vitamin d is often a
clinical diagnosis so
oftentimes clinician will determine the
diagnosis from the history and physical
examination so they can ask the patient
whether they've been taking high
doses of vitamin d supplementation or
ingesting high amounts of fortified
dairy milk
and if that's not the case they can look
into whether there's granulomatous
disease or
even lymphoma there are specific
laboratory investigations that are
helpful as well
these include total calcium ionized
calcium parathyroid hormone levels
and vitamin d levels and again in
vitamin d toxicity we often
find hypercalcemia so calcium levels
greater than 11 milligrams per deciliter
and high vitamin d levels so those high
vitamin d levels
are leading to over activation of
vitamin d pathways
leading to increased absorption of
calcium from the gastrointestinal system
and increased
reabsorption of calcium from the kidneys
we can also do an ekg to assess for a
short qt interval as well so how is
vitamin d toxicity treated
so oftentimes the important point
about treating vitamin d toxicity is
identifying the sources of the
vitamin d so a lot of times that can
come from history
asking the patient whether they've been
ingesting high levels of
vitamin d supplements is one important
question
and then it's important once you
identify the source
to discontinue exogenous vitamin d
sources so
again if it is high levels of
vitamin d supplementation you want to
discontinue those
sources you also want to prevent
excessive bed rest as well
so this helps prevent hypercalcemia of
immobility so if there's already an
issue with hypercalcemia anyway from
vitamin d toxicity
oftentimes clinicians will prevent
excessive bed rest to prevent
worsening or possible worsening of the
hypercalcemia from immobility
iv fluids can also be used to treat the
dehydration
from the vitamin d toxicity as well and
for cases with
severe hypercalcemia where an individual
may have altered mental status
calcitonin and or bisphosphonates can be
used to help reduce the levels of
calcium
and bisphosphonates are stated to be
better
for hypercalcemia malignancy so
calcitonin
and or bisphosphonates are used in the
cases of severe hypercalcemia
so again it's a clinical diagnosis
laboratory investigations
include total calcium ionized calcium
pth and vitamin d levels we see
hypercalcemia in high vitamin d levels
and an ekg is important to
assess for a short qt interval and then
treatment is identifying the sources
and discontinuing those sources
preventing excessive bed rest
iv fluids for dehydration and in the
severe cases of hypercalcemia
calcitonin and bisphosphonates could be
used as well
so that was a lesson on vitamin d
toxicity i hope you found this lesson
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