Hypothyroidism

Question 1

Define

Answer 1

Clinical syndrome resulting from insufficient secretion of thyroid hormones

Question 2

Causes

Answer 2

PRIMARY (↓thyroid hormone production)

• AI thyroiditis (Hashimoto’s): Goitre due to lymphocytic and plasma cell infiltration. Commoner in women aged 60–70yrs. May be hypothyroid or euthyroid; rarely initial period of hyper thyroid (‘Hashitoxicosis’)
  Autoantibody titres are very high
• Primary atrophic hypothyroidism: Diffuse lymphocytic

infiltration of the thyroid, leading to atrophy, hence no goitre

• Severe iodine deficiency (most common worldwide)

Also:
Iatrogenic (post-surgery, radioiodine, medication for hyperthyroidism)
Iodine excess (Wolff-Chaikoff effect)
Thyroiditis or congenital

SECONDARY (not enough TSH)

• Pituitary tumour resulting in ↓TSH and ↓stimulation of

thyroid production

Question 3

Epidemiology

Answer 3

common, 4/1000 per year
F:M, 6:1
Age of onset usually >40 years (but can occur at any age)

Question 4

Symptoms

Answer 4

Onset usually insidious

↘ Cold intolerance, lethargy, weight gain, constipation, cramps, dry skin, hair loss, hoarse voice

↘ Mental slowness, ↓cognition, depression, dementia

↘ Ataxia, paraesthesia

↘ Mental disturbances (menorrhagia, irregular cycles)

↘ Personal or FHx of other AI conditions (e.g. Addison’s,

T1DM)

Myxoedema coma: sever hypothyroidism usually seen in elderly Hypothermia, hypoventilation, hyponatremia, HF, confusion, coma

Question 5

Signs

Answer 5

Hands – bradycardia, cold hands

↘ Head/neck/skin – pale puffy face, goitre, oedema, hair

loss, dry skin, vitiligo

↘ Chest – pericardial or pleural effusions

↘ Abdomen – ascites

↘ Neurological – slow relaxation of reflexes, signs of carpal

tunnel syndrome

Question 6

Investigations

Answer 6

Blood – TFTs
Primary: ↓T4/T3, ↑TSH (due to –ve feedback)

Secondary: ↓T4/T3, ↓or inappropriately normal TSH

FBC: ±macrocytosis, ±normocytic anaemia U&Es: ±↓Na+
Cholesterol: ±↑cholesterol

If suspected 2ndary cause: pituitary function tests, pituitary MRI and visual filed testing

Question 7

Management

Answer 7

Chronic → levothyroxine
Motor response and adjust dose accordingly

Myxoedema coma → O2, rewarming, rehydration, IV T4/T3, IV hydrocortisone, treat underlying disorder

Question 8

Complications

Answer 8

Myxoedema coma
Myxoedema madness (psychosis with delusions and hallucinations or dementia) in severe hypothyroidism – may be seen in the elderly after starting levothyroxine treatment

Question 9

Prognosis

Answer 9

Lifelong levothyroxine replacement therapy required
If treated the prognosis is excellent, if untreated it is disastrous Myxoedema coma has a mortality of up to 80%.