5.13 Hyperthyroidism

Question 1

Where is the thyroxine stored?

Answer 1

In the thyroid follicle which contains thyroglobulin

Question 2

Describe the HPT axis

Answer 2

1. Hypothlamus releases TRH
2. This acts on the thyrotrophs in the pituitary to release TSH
3. They act on thyroid to release T3 and T4
4. These hormones then work by negative feedback to inhibit the pituitary and the hypothalamus at each level

Question 3

What level of TSH will you find a patient with primary hypothyroidism, where the thyroid gland has been destroyed by the immune system?

Answer 3

high TSH

Question 4

How do you control dose of thyroid replacement medications?

Answer 4

Give thyroxine medication
Increase the dose until the TSH falls to normal

Question 5

What is Grave’s disease?

Answer 5

Autoimmune disease
Antibodies bind to and stimulate TSH receptor in thyroid

Question 6

What is the first line investigation to confirm Grave’s disease?

Answer 6

Measure TSH-receptor antibody (TRAb)

Question 7

Describe the typical appears of the thyroid gland in Graves disease

Answer 7

Smooth, diffuse, symmetrical enlargement of the thyroid gland, pain free when swallowing

Question 8

What are the common symptoms of Grave’s Disease?

Answer 8

Pretibital Myxoedema
Exophthalmos
Weight loss
Tremor
Palpitations
Rapid pulse
Agitation
Smooth Goitre

Question 9

What causes exophthalmos of the eye in Grave’s disease?

Answer 9

The antibodies bind to the muscles behind the eye and cause it to pop out the socket

Question 10

What causes pretibial myxoedema in Grave’s disease?

Answer 10

When other antibodies bind to the muscles in the shin and cause hypertrophy of the skin - non pitting swelling

Question 11

Describe the uptake of radioiodine in a patient with Grave’s disease?

Answer 11

Uniform

Question 12

What is toxic nodular thyroid disease?

Answer 12

Single toxic nodule/multiple nodules (multinodular goitre)
A benign adenoma- overactive making too much thyroxine

Question 13

What does not occur in toxic nodular thyroid disease?

Answer 13

NOT autoimmune
NO pretibial myxoedema
NO exophthalmos

Question 14

What is seen in patients with toxic nodular goitre disease?

Answer 14

Unsymmetrical enlargement of the thyroid, with a single hot nodule seen on a radioiodine scan. The other side of the thyroid undergoes atrophy.

Question 15

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

Answer 15

Thyroxine sensitizes the beta adrenoreceptors to the ambient levels of adrenaline and noradrenaline, so there is sympathetic activation

Question 16

What symptoms are seen in hyperthyroidism due to the sympathetic activation?

Answer 16

Tachycadia, palpitations, tremor, and lid lag

Question 17

What causes lid lag?

Answer 17

This is inability of the eyelid to close properly due to the excess adrenaline which is holding the eyelid open

Question 18

Hyperthyroidism symptomss

Answer 18

Weight loss despite increased appetite
Breathlessness
Palpitations, tachycardia
Sweating
Heat intolerance
Diarrhoea
Lid lag

Question 19

What is a thyroid storm?

Answer 19

Severe untreated hyperthyroidism
Medical emergency

Question 20

What are the features of a thyroid storm?

Answer 20

Blood results confirm hyperthyroidism
Fever
Accelerated tachycardia/arrhythmia
Cardiac Failure
Psychosis/delirium
Jaundice

Question 21

What are the three options of treatment for hyperthyroidism?

Answer 21

Drugs
Radiotherapy
Surgery (thyroidectomy)

Question 22

What are the three drugs used to control T4 levels in hyperthyroidism?

Answer 22

Thionamides
Potassium Iodide
Radioiodide

Question 23

What drugs are used for symptomatic control in hyperthyroidism?

Answer 23

NOn-specific Beta blockers to reduce heart rate, tremors

Question 24

How do thionamides work?

Answer 24

They inhibit thyroperoxidase synthesis therefore thyroxine cannot be made

Question 25

What is the name of the most common thionamide?

Answer 25

Carbimazole

Question 26

What is a good non specific beta blocker which is used?

Answer 26

Propranolol

Question 27

What are the unwanted actions of thionamides?

Answer 27

agranulocytosis rashes

Question 28

What is agranulocytosis?

Answer 28

a reduction in neutrophils - patients asked if they have a sore throat as the susceptibility to adaptive infections is higher

Question 29

what is the role of beta blockers in thyrotoxicosis?

Answer 29

It takes several weeks for ATDs to have clinical effects (due to the stored thyroxine in the follicle for up to a month), therefore beta blockers work in the interim

Question 30

When is KI given as a treatment?

Answer 30

prepare hyperthyroid patient for surgery thyroid storm

Question 31

How does KI work as a treatment for hyperthyroidism?

Answer 31

Inhibition of thyroid hormone synthesis due to the Wolff-Chaikoff effect. - the KI inhibits the iodination of TG and therefore inhibits hydrogen peroxide production + thyroperoxidase

Question 32

Why is KI given to hyperthyroid surgery patients?

Answer 32

The gland becomes less vascular and undergoes ATROPHY therefore becomes easier to operate on

Question 33

What are the risks of thyroid surgery?

Answer 33

Risk of voice change due to damage to the recurrent laryngeal nerve Risk of losing parathyroid glands Scar Anaesthetic

Question 34

Which patients cannot use radioiodine?

Answer 34

Pregnant women, and people with kids, people around children as they become radioactive

Question 35

Why is pertechnetate used instead of radioiodine and in what circumstance?

Answer 35

Cheaper- used for scans only, not treatment

Question 36

Negative of radioiodine

Answer 36

Can cause HYPOthyroidism, may need thyroxine after

Question 37

what are the names of the two anti-thyroid drugs?

Answer 37

Carbimazole Propylthiouracil

Question 38

What is viral thyroditis?

Answer 38

When a virus infects the thyroid gland and overrules thyroxine production and results in hyperthyroidism as all the thyroxine which is stored in the follicles is released.

Question 39

How to differentiate between viral thyroditis and Graves?

Answer 39

Viral = painful when swallowing

Question 40

What are the symptoms of viral thyroditis?

Answer 40

Thyroid visibly enlarged on one side Dysphagia, Pain radiating to the ear Pyrexia

Question 41

What is seen on a radioiodine scan of the thyroid in a patient with viral thyroditis?

Answer 41

Nothing as there is no iodine uptake

Question 42

What is seen when monitoring a patient with viral thyroditis over a four month period?

Answer 42

First hyperthyroidism as all the stored thyroxine is released and TSH drops Then hypothyroidism for 2 months as gland stops making thyroxine and just replicates virus (TSH rises) After a further month the disease is resolved

Question 43

How is postpartum thyroditis different to viral thyroditis?

Answer 43

No pain and only occurs after pregnancy as the immune system is modulated during pregnancy