Thyroid Diseases

Question 1

What cells produce thyroid hormones?

Answer 1

Follicular thyroid cells

Question 2

What is the precursor molecule for thyroid hormones?

Answer 2

Thyroglobulin

Question 3

What is iodine bound to in the thyroglobulin?

Answer 3

Tyrosine residues

Question 4

What enzyme binds iodine to tyrosine residues and what is formed?

Answer 4

• Thyroperoxidase (TPO)
• MIT and DIT formed

Question 5

What combinations of MIT and DIT make T3/T4?

Answer 5

• MIT + DIT = T3
• DIT + DIT = T4

Question 6

By what process is T3 made?

Answer 6

Mono-deiodination of T4

Question 7

What enzymes facilitate deiodination of T4?

Answer 7

Deiodinase (D1, D2, D3)

Question 8

Increased or decreased levels of serum TSH, free T4 and free T3 in hyper/hypothyroidism?

Answer 8

• Hyperthyroidism
  > Dec. serum TSH
  > Inc. serum free T4
  > Inc. serum free T3
• Hypothyroidism
  > Inc. serum TSH
  > Dec. serum free T4
  > Dec. serum free T3

Question 9

Aetiology of hyperthyroidism

Answer 9

• Graves’ disease
• Toxic nodular goitre
• Thyroiditis

Question 10

Cause of Graves’ disease

Answer 10

Pathogenic antibodies binding to TSH receptor on thyroid follicular cells

Question 11

5 environmental factors contributing to Graves’ disease

Answer 11

• Gender
• Stress
• Infection
• Pregnancy
• Drugs

Question 12

Symptoms and signs of hyperthyroidism

Answer 12

• Cardiovascular
  > Tachycardia (rapid HR)
  > Atrial fibrillation
  > Shortness of breath
  > Ankle swelling
• Gastrointestinal
  > Weight loss
  > Diarrhoea
  > Increased appetite
• Neurological
  > Tremor
  > Myopathy (weak muscle)
  > Anxiety
• Eye/skin
  > Sore, gritty eyes
  > Double vision
  > Staring eyes
  > Pruritis (itching)

Question 13

Extrathyroidal manifestations of Graves’

Answer 13

• Eyes
  > Lid lag/retraction
  > Conjunctival oedema (swelling)
  > Periorbital puffiness
  > Proptosis (bulging)
  > Ophthalmoplegia (weakness of eye muscles)
• Skin
  > Pretibial myxoedema
  > Acropachy (swollen hands + clubbing)

Question 14

What causes neonatal hyperthyroidism?

Answer 14

TSH-R antibodies cross the placenta during pregnancy

Question 15

Treatments of hyperthyroidism

Answer 15

• Antithyroid drugs (thionamides)
• Surgical removal of thyroid
• Radioiodine therapy

Question 16

Types of thionamides

Answer 16

• Carbimazole
• Propylthiouracil

Question 17

How do thionamides work?

Answer 17

Block iodine incorporation through inhibition of thyroperoxidase

Question 18

Side effects of thionamides

Answer 18

• Rash
• Joint pains
• Sickness
• Agranulocytosis (no WBCs)
• Liver disease (propylthiouracil)
• Pancreatitis (carbimazole)

Question 19

Risks of radioiodine therapy

Answer 19

• Hypothyroidism
• Cancer
• Infertility
• Teratogenesis
• Worsen eye disease

Question 20

Aetiology of hypothyroidism

Answer 20

• Hashimoto thyroiditis (autoimmune)
• After treatment for hyper
• Iodine deficiency
• Subacute/silent thyroiditis

Question 21

Symptoms and signs of hypothyroidism

Answer 21

• Cardiovascular
  > Bradycardia (slow HR)
  > Heart failure
  > Pericardial effusion
• Skin
  > Myxoedema (swelling of skin and underlying tissue)
  > Rash on legs
  > Vitiligo
• Gastrointestinal
  > Weight gain
  > Constipation
• Neurological
  > Depression
  > Psychosis
  > Cold intolerance
  > Carpal tunnel syndrome

Question 22

What may thyroid nodules cause?

Answer 22

• Thyroid dysfunction
• Compression

Question 23

Prevalence of malignancy in thyroid nodules

Answer 23

4-6.5%

Question 24

Features suggestive of malignancy in thyroid nodules

Answer 24

• Age <20 or >60
• Firmness of nodule
• Rapid growth
• Fixation to adjacent structures
• Vocal cord paralysis

Question 25

Steps of investigation of thyroid nodules

Answer 25

1. Assessment of thyroid function
2. Assessment of thyroid size
3. Assessment of thyroid pathology

Question 26

Aetiology of thyroid cancer

Answer 26

• External radiation
• Iodine deficiency
• Oncogene expression
• Genetic factors