Endo 5 - Hyperthyroidism

Question 1

Describe Plummers disease (a form of hyperthyroidism)

Answer 1

1. Toxic nodular goitre caused by benign adenomas

2. NOT AUTOIMMUNE - therefore no exophthalmos or pretibial myxoedema

Question 2

What does thyroxine do to the SNS

Answer 2

It sensitises the Beta receptors = little bit of A/NA has massive effects

Looks like there is SNS activation, may manifest as palpitations, tremor, lid lag etc

Question 3

If someone has a family history of hyperthyroidism, its more likely to be graves or plummers?

Answer 3

Graves (as autoimmune aspect)

Question 4

What are some common symptoms of hyperthyroidism?

Answer 4

Weight loss w increased appetite
Breathlessness
Palpitations/tachycardia
Sweating
Heat intolerance
DIarrhoea
Lid lag

Question 5

Thyroid storm is what?

requires aggressive treatment

Answer 5

Extreme hyperthyroidism with 2 of the following 5:

1. Hyperpyrexia > 41*C
2. Accelerated tachycardia
3. Cardiac failur
4. Delirium/ psychosis
5. Hepatocellular dysfunction - jaundice

Question 6

What are the treatment options for hyperthyroidism?

Answer 6

Surgery / radioiodine / drugs

Question 7

What are the 4 classes of drugs used to treat hyperthyroidism?

Answer 7

1. Thionamides (propylthiouracil (PTU) / Carbimazole (CBZ))
2. Potassium iodide
3. Radioiodine
4. Beta blockers

1-3 = reduce thyroid hormone synthesis

4 = symptoms relief

Question 8

When would you use thionamides?

Answer 8

1. Daily treatment of hyperthyroid conditions, or before surgery or short term while waiting for radioactive iodine to act

Question 9

How do thionamides (aka anti-thyroid drugs) work?

Answer 9

Inhibit thyroid peroxidase enzymes - slows down T3/4 synthesis and secretion

Question 10

How long do thionamides take to have a clinical effect?

Answer 10

Weeks, although biochemical effect within hours

Question 11

Does hyperthyroidism require a cardioselective or non-cardioselective B blocker?

Answer 11

Non cardioselective - e.g. propranolol

Question 12

Thionamides may do 2 other things in addition to inhibiting peroxidase enzymes. They are?

Answer 12

1. Suppress antibody production in graves disease

2. PTU may reduce conversion of T4 to T3 peripherally

Question 13

What are some unwanted actions of antithyroid drugs

Answer 13

1. Agranulocytosis (reduction in neutrophils) - rare and reversible if drug withdrawn
2. Rashes (common)

Question 14

PTU and Carbimazole are antithyroid drugs (thionamides). They are orally active. When pregnant, what must you consider?

Answer 14

Both PTU and carbimazole cross the placenta and are secreted in breastmilk, so lower doses. PTU crosses less into placenta and less secreted, so PTU preferred

Question 15

Carbimazole is a prodrug which is converted into?

Answer 15

Methimazole

Question 16

Where are antithyroid drugs metabolised and excreted?

Answer 16

Metabolised in liver and excreted in urine

Question 17

How long should antithyroid treatment be?

Answer 17

18 months, then periodically check for relapse

Question 18

When would you give KI to a patient

Answer 18

In severe thyrotoxic crisis

Or to prepare a hyperthyroid patient for surgery

Question 19

Explain the mechanism of action of KI

Answer 19

1. Inhibits iodination of thyroglobulin
2. Inhibits thyroperoxidase and peroxide generation

WOLFF-CHAIKOFF effect - auto regulatory effect whereby body shuts down T4 production if exposed to too much iodine

Question 20

How long does KI take to work?

Answer 20

Symptom reduction in 1-2 days

Vascularity and size reduction of thyroid in 10-14 days

KI ONLY USED VERY SHORT TERM

Question 21

What are the unwanted actions of KI?

Answer 21

1. Allergic reaction

Question 22

When is radioiodine given?

Answer 22

When antithyroid drugs don’t work after 18 months.

Question 23

How does radio iodine work?

Answer 23

Accumulates in colloid, emits B particles and destroys follicular cells

Question 24

How is radio iodine given?

Answer 24

Given asa single oral dose

Question 25

What must you be cautious about when giving radio iodine?

Answer 25

Contraindicated in pregnancy and breast feeding, avoid if near small children for 2 weeks

Question 26

What is viral thyroiditis?

Answer 26

Virus attacks thyroid gland and causes colloid leakage

Thyroid stops making thyroxine and makes viruses instead, so no iodine uptake

Question 27

What are the symptoms of viral thyroiditis

Answer 27

1. Painful dysphagia
2. Hyperthyroidism
3. Pyrexia
4. Raised ESR

Question 28

What is a classical sign of viral thyroiditis

Answer 28

NO RADIOIODINE UPTAKE

Initial hyperthyroidism, then one month later, hypothyroidism (As thyroxine stores exhausted)

Question 29

How do you treat viral thyroiditis

Answer 29

Leave them alone, it will resolve after 2 months