Hyperthyroidism

Question 1

What inhibits TRH and therefore TSH?

Answer 1

T4 and T3

Question 2

What is Graves’ disease?

Answer 2

Autoimmune
Antibodies bind and stimulate the TSH receptor in the thyroid
Causing a smooth goitre and hyperthyroidism

Question 3

What are common symptoms of Graves’ disease?

Answer 3

Exophthalmos

Pretibial myxoedema

Question 4

What causes exophthalmos in people with Graves’ disease?

Answer 4

Antibodies binding to the muscles behind the eye

Question 5

What is pretibial myxoedema?

Answer 5

The swelling (non-pitting) that occurs on the shins of patients with Graves' disease (growth of soft tissue)
associated with hyperthyroidism NOT hypothyroidism

Question 6

Describe the goitre caused by Graves’ disease.

Answer 6

Diffuse enlargement and engorgement of the thyroid gland

with uniform radioiodine uptake

Question 7

What is the difference between Plummer’s disease and Graves’ disease?

Answer 7

Plummers is:

• not autoimmune
• no pretibial myxoedema
• no exophthalmos
• non-symmetrical and non-diffuse goitre

Question 8

What is Plummer’s disease?

Answer 8

Characterised by:

• toxic nodular goitre
• benign adenoma (overactive) produces excess thyroxine

Question 9

How does thyroxine impact the sympathetic nervous system?

Answer 9

It sensitises beta adrenoreceptors to the ambient levels of adrenaline and noradrenaline - causing apparent sympathetic activation.

Question 10

How does the impact of thyroxine on the sympathetic nervous system present?

Answer 10

• tachycardia
• palpitations
• tremor in the hands
• lid lag

Question 11

What are the symptoms of hyperthyroidism?

Answer 11

• weight loss (despite increased appetite)
• breathlessness
• palpitations
• tachycardia
• sweating
• heat intolerance
• diarrhoea
• lid lag (+ other sympathetic features)

Question 12

What is a thyroid storm?

Answer 12

A medical emergency resulting in a 50% mortality if untreated
(aggressive treatment is required)

Question 13

What are the characteristics of a thyroid strom?

Answer 13

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

Question 14

What are the possible treatments for hyperthyroidism?

Answer 14

• surgery (thyroidectomy)
• radioiodine
• drugs

Question 15

What are the 4 classes of drugs involved in the treatment of hyperthyroidism?

Answer 15

Thionamides (thiourylenes; anti-thyroid drugs)
- propylthiouracil (PTU)
- carbimazole (CBZ)
Potassium Iodide
Radioiodine
Beta-Blockers

Question 16

What is the aim of thionamides, potassium iodide and radioiodine?

Answer 16

To reduce thyroid hormone synthesis

Question 17

What is the aim of Beta-blockers?

Answer 17

To help with the symptoms associated with hyperthyroidism

Question 18

What are the 2 main hormones involves in thyroid hormone synthesis?

Answer 18

• Thyroperoxidase

- Peroxidase transaminase

Question 19

What is the mechanism of action of thionamides?

Answer 19

The inhibition of thyroid peroxidase and therefore T3/4 synthesis and secretion

Question 20

How long does it take for thionamides to come into effect?

Answer 20

biochemical effect: hours

clinical effect: weeks

Question 21

What drug often accompanies thionamides in a treatment plan?

Answer 21

Propanolol (beta-blockers)

rapidly reduces tremors, and tachycardia

Question 22

Describe the synthesis of thyroid hormones

Answer 22

• Uptake of iodide via active transport
• Iodination
• Coupling reaction: storage in the colloid
• Endocytosis and secretion

Question 23

What are the symptoms of hyperthyroidism?

Answer 23

• weight loss (despite increased appetite)
• breathlessness
• palpitations
• tachycardia
• sweating
• heat intolerance
• diarrhoea
• lid lag (+ other sympathetic features)

Question 24

What is a thyroid storm?

Answer 24

A medical emergency resulting in a 50% mortality if untreated
(aggressive treatment is required)

Question 25

What are the characteristics of a thyroid strom?

Answer 25

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

Question 26

What are the possible treatments for hyperthyroidism?

Answer 26

- surgery (thyroidectomy) - radioiodine - drugs

Question 27

What are the 4 classes of drugs involved in the treatment of hyperthyroidism?

Answer 27

``` Thionamides (thiourylenes; anti-thyroid drugs) - propylthiouracil (PTU) - carbimazole (CBZ) Potassium Iodide Radioiodine Beta-Blockers ```

Question 28

What is the aim of thionamides, potassium iodide and radioiodine?

Answer 28

To reduce thyroid hormone synthesis

Question 29

What is the aim of Beta-blockers?

Answer 29

To help with the symptoms associated with hyperthyroidism

Question 30

What are the 2 main hormones involves in thyroid hormone synthesis?

Answer 30

- Thyroperoxidase | - Peroxidase transaminase

Question 31

What is the mechanism of action of thionamides?

Answer 31

The inhibition of thyroid peroxidase and therefore T3/4 synthesis and secretion

Question 32

When is radioiodine contrindicated?

Answer 32

Pregnancy

Question 33

What drug often accompanies thionamides in a treatment plan?

Answer 33

Propanolol | rapidly reduces tremors, and tachycardia

Question 34

Describe the synthesis of thyroid hormones

Answer 34

- Uptake of iodide via active transport - Iodination - Coupling reaction: storage in the colloid - Endocytosis and secretion

Question 35

What are the unwanted actions of thionamides?

Answer 35

- rashes (common) | - Agranulocytosis (normally a reduction in neutrophils) - rare, and reversible by stopping the drug

Question 36

How to follow up on the patient using drugs to treat hyperthyroidism?

Answer 36

- aim to stop the anti-thyroid drug treatment after 18 months - review patient periodically, including thyroid function tests for remission/relapse.

Question 37

Why are beta-blockers like propanolol involved in treatment plans with anti-thhyroid drugs?

Answer 37

Anti-thyroid drugs take several weeks to have clinical effects, therefore non-selective beta-blockers do so in the interim.

Question 38

When is potassium iodide used?

Answer 38

- in preparation for surgery - during a thyroid storm (severe thyrotoxic crisis) usually in doses >30x daily requirement

Question 39

What is the mechanism of action of potassium iodide?

Answer 39

- Inhibits the iodination of thyroglobulin | - Inhibits hydrogen peroxide generation and thyroperoxidase

Question 40

What is the impact of potassium iodide in hyperthyroidism?

Answer 40

- inhibition of thyroid hormone synthesis and secretion - Wolff-Chaikoff effect - hyperthyroid symptoms reduce in 1-2 days - vascularity and size of the gland reduce in 10-14 days

Question 41

What is the Wolff-Chaikoff effect?

Answer 41

A presumed auto-regulatory effect

Question 42

What are the risks involved in surgery/thyroidectomy?

Answer 42

- risk of voice change - risk of parathyroid gland loss - scarring - risk involved in anaesthesia

Question 43

What is the process involved in radioiodine?

Answer 43

- swallow a capsule containing 370MBq (10mCi) of the isotope I (131) - need to avoid children and pregnant mums for a few days - for scans ONLY: 99-Tc pertechnetate is an option

Question 44

When is radioiodine contrindicated?

Answer 44

- pregnancy

Question 45

What are the symptoms of Viral (de Quervain's) thyroiditis?

Answer 45

- painful dysphagia - hyperthyroidism - pyrexia - thyroid inflammation - one-sided visible enlargement of the thyroid gland

Question 46

What causes Viral (de Quervain's) thyroiditis?

Answer 46

- virus attacks the thyroid gland causing pain and tenderness - thyroid stops making thyroxine and makes viruses instead - therefore no iodine uptake (ZERO) - stored thyroxine is released - thus, toxic with 0 reuptake - 4 weeks later, stores are exhausted > hypothyroidism - 8 weeks later, resolution occurs - patient becomes euthyroid

Question 47

How does Viral (de Quervain's) thyroiditis present?

Answer 47

- painful neck - all stored thyroxine is released - fT4 levels rise - TSH levels drop - 1 month of hyperthyroidism - no new thyroxine synthesis - fT4 slowly falls - patients becomes hypothyroid (thyroid just replicates the virus) lasts another month - after 3 months, slow recovery

Question 48

What is the difference between viral (de Quervain's) thyroiditis and postpartum thyroiditis?

Answer 48

postpartum thyroiditis has no pain, and only occurs post pregnancy