Hypothyroidism and Hashimoto's Thyroiditis: Visual Explanation for Students

hi this is tom from zero to finals calm

in this video I'm going to be talking

about hypothyroidism you can find

written notes on this topic at zero da

finals comm slash hypothyroidism or in

the endocrinology section of the zero to

finals Medicine book let's jump straight

in hyperthyroidism is the term used to

describe inadequate output of thyroid

hormones by the thyroid gland there's a

few different causes the most common

cause of hyperthyroidism in the

developed world is Hashimoto's

thyroiditis and this is caused by

autoimmune inflammation of the thyroid

gland so the body's immune system

attacking the thyroid gland it's

associated with anti-thyroid peroxidase

or anti TPO antibodies and also with

anti thyroid globulin antibodies

initially it causes a bit of a goiter

after which there's atrophy of the

thyroid gland as the hyperthyroidism

sets in iodine deficiency is the most

common cause of hyperthyroidism in the

developing world and this is because

iodine is essential for the production

of thyroid hormones iodine is added to

foods like table salt to prevent iodine

deficiency and to prevent hypothyroidism

hyperthyroidism can also occur as a

result of treatment for hyperthyroidism

so all the treatments for

hyperthyroidism have the potential to

overshoot and cause hypothyroidism so

these are treatments like kaboom azole

propath io uracil radioactive iodine and

of course thyroid surgery there are also

medications that can cause

hyperthyroidism lithium inhibits the

production of thyroid hormones in the

thyroid gland and so can cause a goiter

and hypothyroidism amiodarone interferes

with the thyroid hormone production and

metabolism and usually it causes a


but it can also cause a thorough

toxicosis there's also secondary causes

of hyperthyroidism or central causes and

this is where the pituitary gland is

failing to produce enough TSH and this

is often associated with a lack of other

pituitary hormones as well such as ACTH

and this is called hypopituitarism and

it has quite a few different causes and

these causes can be tumors of the

pituitary gland infections in that area

vascular pathology such as something

called Sheehan syndrome where you get

pituitary necrosis

after massive blood loss during child

and radiation therapy to the pituitary

gland so how do patients with

hypothyroidism present well they can

present with weight gain fatigue dry

skin coarse hair and hair loss they can

have fluid retention so they can develop

a Deemer or pleural effusions or ascites

they can have amenorrhea so the periods

stop and it can slow down the bowels and

make the very constipated so when you

suspect hypothyroidism how do you

investigate them well firstly you would

do a TSH find that the TSH is abnormal

and then do t3 and t4 levels in primary

hypothyroidism this is caused by a

thyroid gland insufficiency so the

thyroid hormones like t3 and t4 will be

low and the TSH level will be high

because there's no negative feedback to

the pituitary gland

so the Petrucci produces lots of TSH to

try and get the thyroid working again in

secondary hypothyroidism it's caused by

pituitary pathology and that results in

a low production of TSH

so TSH will be low and the thyroid

hormones will be low how do we manage


well it's quite straightforward we

simply replace the thyroid hormone that

isn't there with oral lever thyroxine so

we give them oral thyroid hormone in the

form of levothyroxine levothyroxine is

synthetic t4 and it metabolizes in the

body to t3 so you get t4 and t3 from

this one medication the doses are

titrated until TSH levels are normal so

when you start lever thyroxine initially

measure the TSH levels monthly until the

TSH level is stable and then once stable

it can be checked less frequently unless

the patient becomes symptomatic so if

the TSH level is high you know the dose

of levothyroxine is too low so it needs

to be increased and if the TSH level is

low you know that the dose of

levothyroxine is too high and it needs

to be reduced

so thanks for watching I hope you found

this video helpful if you did don't

forget there's plenty of other resources

on the zero to finals website including

loads and loads of notes on various

different topics that you might cover in

medical school with specially made

illustrations there's also a whole test

section where you can find loads of

questions to test your knowledge and see

where you're up to in preparation for

your exams

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