Hyperthyroidism

Question 1

What are two common causes of hyperthyroidism?

Answer 1

Graves' disease
Nodular goitre (Plummer's disease)

Question 2

What is Graves’ disease?

Answer 2

Autoimmune disease- antibodies bind to and stimulate TSH receptor in thyroid. This makes the thyroid overreactive and this leads to the thyroid becoming smoothly enlarged (goitre) and you get hyperthyroidism

Question 3

In terms of the eyelids, how can you tell if a person has hyperthyroidism?

Answer 3

It causes lid lag (delay in eyelid moving down as you look down)

Question 4

How does a patient with Graves’ normally present?

Answer 4

Overactive
Anxious
Rapid pulse
Warm
Localised pretibial myxoedema 
Exopthalamos

Question 5

What is localised pretibial myxoedema?

Answer 5

Swelling of soft tissue in shins due to antibody binding to receptor

Question 6

What is exopthalmos?

Answer 6

Another antibody binds to growth factor receptors behind the eye so muscles behind the eye grow and push the eye forward

Question 7

What makes exopthalmos worse?

Answer 7

Smoking

Question 8

What is the thyroid gland of someone with Graves’ like?

Answer 8

Very diffuse and smoothly enlarged

Question 9

How can you image the thyroid?

Answer 9

By giving a patient radioactive iodine which will show up on a scintigram

Question 10

What is Plummers disease?

Answer 10

Toxic nodular goitre- part of the thyroid has become tumorous and is misbehaving

Question 11

What is Plummer’s disease caused by?

Answer 11

A benign adenoma that is overactive at making thyroxine

Question 12

What is the thyroid gland of someone with Plummer’s like?

Answer 12

There will be a visible lump on one side

Question 13

What will you see if you do an iodine scan on someone with Plummer’s?

Answer 13

It will show the iodine going into the hot tumour. Because there is so much thyroxine coming from the tumour, the pituitary will stop making TSH and the rest of the thyroid will shrink away and stop making thyroxine so only the nodule is visible

Question 14

What is the effect of thyroxine on the sympathetic nervous system?

Answer 14

It sensitises beta adrenoceptors to adrenaline and noradrenaline so normal amounts will have much stronger effects

Question 15

What does the effect of thyroxine on sympathetic nervous system cause in patients?

Answer 15

Effects of too much adrenaline:
Palpitations
Heart tremors
Tachycardia
Lidlag

Question 16

Give a brief summary of the symptoms of hyperthyroidism

Answer 16

Weight loss despite increased appetite 
Breathlessness
Tachycardia
Sweating
Heat intolerance
Diarrhoea
Lid lag

Question 17

What is a thyrotoxic crisis known as?

Answer 17

Thyroid storm

Question 18

What is the mortality of a thyroid storm if untreated?

Answer 18

50%

Question 19

What are the features of a thyroid storm?

Answer 19

Hyperpyrexia
Accelerated tachycardia/arrhythmia
Cardiac failure
Delirium
Hepatocellular dysfunction/jaundice

Question 20

What is hyperpyrexia?

Answer 20

Temperature > 41 degrees

Question 21

What is the treatment for a thyroid storm?

Answer 21

Surgery
Radioiodine
Drugs

Question 22

What sort of drugs are used to treat hyperthyroidism?

Answer 22

Thionamides- Propylthiouracil and Carbimazole
Potassium iodide
Radioiodine
Beta blockers

Question 23

When are thionamides specifically given?

Answer 23

Before thyroidectomy because you don’t want to give a general anaesthetic to someone who is tachycardic
Following radioactive iodine treatment

Question 24

How are thyroid hormones synthesised?

Answer 24

Iodine is taken up into follicular cells
Under the action of thyroperoxidase with hydrogen peroxide you get iodination of tyrosine residues in the thyroglobulin
You then get coupling of monoiodotyrosine and diiodotyrosine to form T3 and T4
This is taken up and released by cells into the circulation

Question 25

What do thionamides do?

Answer 25

They inhibit thyroperoxidase hence inhibit iodination of tyrosine residues and coupling of tyrosine residues So leads to reduction in production and secretion of T3 and T4

Question 26

How long does it take for both the biochemical and clinical effects of thionamides take to become evident?

Answer 26

Biochemical- Hours | Clinical- A few weeks

Question 27

Why is there this relationship between biochemical and clinical presentation?

Answer 27

There is a lot of stored thyroid hormone in follicular cells and the anti thyroid treatment only affects synthesis not storage

Question 28

Due to the delayed clinical effect of thionamides, how would you deal with the symptoms in the short term?

Answer 28

Non-selective beta blocker

Question 29

What are some other effects of anti thyroid hormones?

Answer 29

Suppress antibody production in Graves disease | Reduces the deiodination of T4 to T3 in peripheral tissues (done by propylthiouracil)

Question 30

What are the unwanted effects of thionamides?

Answer 30

``` Agranulocytosis/granulocytopenia Rashes Headaches Nausea Jaundice Joint pain ```

Question 31

Why are there concerns relating to pregnancy with thyroid disorder?

Answer 31

It is common in women around reproductive age and thionamides are able to cross the placenta and are secreted in the milk which can lead to foetal hypothyroidism

Question 32

Why would a breastfeeding woman be put on PTU over carbimazole?

Answer 32

PTU crosses into the breast milk less than carbimazole

Question 33

Why is the beta blocker that you use to treat the symptoms non-selective?

Answer 33

Reduces all the effects of excess stimulation of beta adrenoceptors

Question 34

When is iodine used as treatment for hyperthyroidism?

Answer 34

Preparation of patients for surgery | Severe thyroid storm

Question 35

How does iodine treatment work?

Answer 35

You give such a large dose that the thyroid switches off because inhibits iodination of thyroglobulin and generation of hydrogen peroxide

Question 36

What is the Wolff-Chaikoff effect?

Answer 36

There is temporary reduction in thyroid hormones following ingestion of large amounts of iodine

Question 37

Why does the Wolf-Chaikoff effect occur?

Answer 37

It is autoregulatory, it occurs to prevent the thyroid form making too much thyroid hormone

Question 38

How does iodine compare to thionamides in terms of time required for effects to be seen?

Answer 38

Iodine is quicker

Question 39

What are the unwanted actions of iodine treatment?

Answer 39

Allergic reaction Rashes Fever Angioedema

Question 40

How is iodine administered?

Answer 40

Lugol's solution or aqueous

Question 41

What is radioiodine used to treat?

Answer 41

Graves', Plummer's and thyroid cancer

Question 42

What does radioiodine treatment do?

Answer 42

Permanently switches off the thyroid without needing surgery

Question 43

How does radioiodine work?

Answer 43

Thyroid follicular cells take up the iodine and it accumulates in the colloid, from there, it emits beta particles of radiation that destroy the follicular cells

Question 44

7-10 days before radioiodine treatment, anti thyroid drugs are stopped, why is this?

Answer 44

This is so that the thyroid gland can become incredibly active so that it will take up a lot of the iodine when it is administered and maximum damage can be achieved

Question 45

What is technetium 99 pertechnetate used for?

Answer 45

Thyroid uptake scans

Question 46

How does the thyroid uptake scan for Graves look like?

Answer 46

Whole thyroid is active and smoothly enlarged

Question 47

How does the thyroid uptake scan for Plummers/Toxic nodule look like?

Answer 47

Single focus of activity and rest is suppressed

Question 48

How does the thyroid uptake scan for thyroiditis look like?

Answer 48

Whole thyroid is unhappy, enlarged and inactive

Question 49

Which drug reduces the size and vascularity of the thyroid gland?

Answer 49

Iodine

Question 50

What are the symptoms of viral thyroiditis?

Answer 50

``` Dysphagia Pyrexia Malaise Pain radiating to the ear Thyroid gland visibly enlarged and tender (on one side) ```

Question 51

How does viral thyroiditis occur?

Answer 51

A virus attacks the thyroid and causes fever, it also damages the thyroid follicles and stored thyroxine is released. So gland is being damaged and prevented from making any new thyroxine but prevents as an overactive thyroid

Question 52

What do you see in a technetium scan for viral thyroiditis?

Answer 52

There is no iodine uptake so you don't see anything

Question 53

How do you treat viral thyroiditis?

Answer 53

The patient just has to wait for about month until all the stored thyroxine has ran out and will be hypothyroid until their cells recover