Hyperthyroidism

Question 1

Draw the control of thyroid activity

Answer 1

Question 2

What is Grave’s disease?

Answer 2

Autoimmune
Antibodies bind to and stimulate the TSH receptor in the thyroid
Cause goitre (smooth) and hyperthyroidism

Question 3

What are the symptoms of Grave’s disease?

Answer 3

Question 4

What is Exophthalmos?

Answer 4

Other antibodies bind to muscles behind the eye and cause exophthalmos

Question 5

What is pretibial myxoedema (hypertrophy)

Answer 5

The swelling (non-pitting) that occurs on the shins of patients with Graves’ disease: growth of soft tissue.

Not to be confused with myxoedema=hypothyroidism

Question 6

What happens to the goitre in Grave’s disease?

Answer 6

Diffuse goitre of moderate size and uniform radioiodine uptake

Diffuse enlargement and engorgement of thyroid gland (broken line indicates normal size of gland)

Question 7

What is Plummer’s disease

Answer 7

Toxic nodular goitre
NOT autoimmune
Benign adenoma that is overactive at making thyroxine.
NO pretibial myxoedema
NO exophthalmos

Question 8

What are the effects of thyroxine on the sympathetic nervous system

Answer 8

Sensitises beta adrenoceptors to ambient levels of adrenaline and noradrenaline.
Thus there is apparent sympathetic activation
Tachycardia, palpitations, tremor in hands, lid lag

Question 9

What are the symptoms of hyperthyroidism?

Answer 9

Weight loss despite increased appetite
Breathlessness,
palpitations, tachycardia
Sweating
Heat intolerance
Diarrhoea
Lid lag and other sympathetic features

Question 10

What is thyroid storm?

Answer 10

Hyperpyrexia > 41oC
accelerated tachycardia / arrhythmia
cardiac failure
delirium / frank psychosis
hepatocellular dysfunction; jaundice

Any 2 confirm thyroid storm
Blood results confirm hyperthyroidism
Needs aggressive treatment

Question 11

How can you treat thyroid storm?

Answer 11

Surgery (thyroidectomy)
Radioiodine
Drugs

Question 12

What are the classes of drugs used in the treatment of hyperthyroidism

Answer 12

1. The thionamides (thiourylenes; anti-thyroid drugs)
   - propylthiouracil (PTU)
   - carbimazole (CBZ)
2. Potassium Iodide
3. Radioiodine
4. β-blockers

First 3 drugs reduce thyroid hormone synthesis
B blockers help with symptoms

Question 13

How do thionamides work?

Answer 13

It inhibits thyroid peroxidase (enzyme that makes thyroxine) and hence T3/4 synthesis and secretion

Biochemical effect - hours
Clinical effect - week

Treatment may include propranolol - rapidly reduces tremor, tachycardia

Question 14

What are the side effect of thionamides ?

Answer 14

Agranulocytosis (usually reduction in neutrophils) - rare and reversible on withdrawal of drug.
Rashes (relatively common)

Question 15

What does the follow up of hyperthyroidism involve?

Answer 15

Usually aim to stop anti-thyroid drug treatment after 18 months

Review patient periodically including thyroid function tests for remission/relapse

Question 16

What is the role of b blockers in thyrotoxicosis?

Answer 16

Several weeks for ATDs to have clinical effects eg reduced tremor, slower heart rate, less anxiety
NON-selective (ie b1 & b2) b blocker
eg propranolol
achieves these effects in the interim

Question 17

What is the purpose of Potassium Iodide?

Answer 17

Preparation of hyperthyroid patients for surgery
Used for severe thyrotoxic crisis (thyroid storm)

Question 18

What are the problems with surgery for hyperthyroidism?

Answer 18

Risk of voice change
Risk of also losing parathyroid glands
Scar
Anaesthetic

Question 19

How does radioiodine work?

Answer 19

Swallow a capsule containing about 370 MBq (10 mCi) of the isotope I (131)
Contraindicated in pregnancy
Need to avoid children and pregnant mums for a few days
For scans only (not treatment), 99-Tc pertechnetate is an option.

Question 20

What does Viral (de Quervain’s) thyroiditis involve?

Answer 20

Painful dysphagia
Hyperthyroidism
Pyrexia
Thyroid inflammation

Question 20

Summarise the treatment options for hyperthyroidism

Answer 20

Drugs:
-Beta blockade is VERY IMPORTANT
-propranolol
Anti thyroid drugs :
-Carbimazole
-Propylthiouracil

Radioiodine
Surgery (partial thyroidectomy)

Question 21

How does Viral (de Quervain’s) thyroiditis work?

Answer 21

Virus attacks thyroid gland causing pain and tenderness
Thyroid stops making thyroxine and makes viruses instead
Thus no iodine uptake (ZERO)

Radioiodine uptake zero
Stored thyroxine released
Thus toxic with zero uptake

Four weeks later, stored thyroxine exhausted, so hypothyroid.

After a further month, resolution occurs (like in all viral diseases).

Patient then becomes euthyroid again.

Question 22

Viral (de Quervain’s) thyroiditis
What happens when virus attacks thyroid gland?
What happens when FT4 slowly falls…

Answer 22