PBL 3 - Hypothyroidism

Question 1

What are the causes of hypothyroidism? (7)

Answer 1

1. Autoimmune (90%)
   a. Hashimoto’s thyroiditis
   b. Spontaneous atrophic hypothyroidism
2. Iatrogenic
   a. Radioactive iodine treatment
   b. Thyroidectomy
   c. Other thyroid drugs
3. Transient thyroiditis
4. Iodine deficiency
5. Congenital
   a. Thyroid aplasia
6. Infiltrative
   a. Amyloidosis
   b. Sarcoidosis
7. Secondary hypothyroidism
   a. TSH deficiency

Question 2

Describe the pathophysiology of hypothyroidism. (3)

Answer 2

1. Insufficient thyroid hormones
2. Effect of decreased thyroid hormones:
   a. Decreased metabolism
   b. Myxoedema
3. Mexoedematous coma
   a. Carbon dioxide retention and coma
   b. Fluid and electrolyte imbalance
   c. Hypothermia

Question 3

Describe the symptoms of hypothyroidism. (9)

Answer 3

1. Weight gain
2. Facial features:
   a. Purplish lips
   b. Malar flush
   c. Periorbital oedema
   d. Loss of lateral oedema
3. Cold intolerance
4. Fatigue
5. Dry skin
6. Dry hair
7. Menorrhagia
8. Depression
9. Psychosis

Question 4

Describe the clinical signs of hypothyroidism. (10)

What is the pnemonic?

Answer 4

“BRADYCARDIC”:

Bradycardia
Reflexes slow (hyporeflexia)
Ataxia (cerebellar)
Dry, thin hair/skin
Yawning/drowsy/coma
Ascites and non-pitting oedema
Round, puffy face
Defeated demeanour
Immobile/ileus
Chronic heart failure

Question 5

List the investigations that can be done for hypothyroidism. (2)

Answer 5

1. TSH levels

2. Free serum T4 levels

Question 6

Define Hashimoto’s thyroiditis.

Answer 6

Chronic inflammation of the thyroid gland due to the formation of antibodies against normal thyroid tissue

Question 7

Describe the pathophysiology of Hashimoto’s thyroiditis. (2)

Answer 7

1. Total destruction of the thyroid due to an immunological process
2. Autoantibodies are produced and act against the thyroid
   a. Anti-thyroid peroxidase (anti-TPO) Ab
   b. Anti-nuclear factor
   c. Anti-TSH receptor antibodies

Question 8

Describe the treatment of hypothyroidism. (1)

What are the side effects? (2)

What are the contraindications? (3)

Answer 8

Levothyroxine

SIDE EFFECTS:
Increased risk of osteoporosis
Atrial fibrillation

CONTRAINDICATIONS:
PPIs
Ferrous sulphate
Calcium supplements

Question 9

List 5 causes of congenital hypothyroidism.

Answer 9

Thyroid dysgenesis, e.g.
-Abnormal TSH receptor

Dyshormonogenesis, e.g.

• Thyroid peroxidase
• Thyroglobulin
• Sodium iodide symporter
• Pendrin

Question 10

What is Pendred syndrome?

Answer 10

Congenital hypothyroidism due to abnormalities in pendrin

Question 11

Describe the clinical features of congenital hypothyroidism (cretinism). (9)

Answer 11

Coarse facial features
Macroglossia
Large fontanelles
Umbilical hernia
Mottled/cool/dry skin
Developmental delay
Pallor
Myxoedema
Goitre

Question 12

What is hypothyroidism associated with? (6)

Answer 12

Other autoimmune diseases, e.g.

• T1DM
• Addison’s disease
• Pernicious anaemia
• Vitiligo

Genetic disorders, e.g.

• Down’s syndrome
• Turner’s syndrome

Question 13

What do you call iodine induced hypothyroidism?

Answer 13

Wolff Chaikoff effect