Hypothyroidism

Question 1

Define Hypothyroidism

Answer 1

Syndrome resulting from insufficient secretion of thyroid hormones (T4 and T3)

Primary (95%): failure of the thyroid gland to produce thyroid hormones

Secondary (5%): Underproduction of TSH by the pituitary gland

Question 2

Aetiology of Hypothyroidism

Answer 2

Primary (95%):
Autoimmune (Hashimoto’s) thyroiditis
Iatrogenic (post-surgery, radioiodine, hyperthyroidism treatment)
Severe iodine deficiency or iodine excess (Wolff-Chaikoff effect)
Thyroiditis (DeQuervain’s)
Thyroid dysgenesis
Drugs (lithium, amiodarone etc.)

Secondary
Pituitary or hypothalamic disease e.g. tumours

Question 3

Risk factors for Hypothyroidism

Answer 3

Iodine deficiency 
Female
Middle age
Family history of autoimmune thyroiditis
Autoimmune disorders
Graves
Post-partum thyroiditis
Turner's and Down's
Primary pulmonary hypertension
MS
Radiotherapy

Question 4

Epidemiology of Hypothyroidism

Answer 4

Developing world - iodine deficiency is a major cause

Hashimoto’s affects women 8-9x more

Question 5

Symptoms of Hypothyroidism

Answer 5

Cold intolerance
Deepening voice 
Constipation
Bradycardia
Weakness or myalgia 
Lethargy, depression
Weight gain (but reduced appetite)
Menstrual irregularity 
Eyelid or facial oedema, dry or coarse skin
Thick skin

Question 6

What are the symptoms and signs of Myxoedema coma

Answer 6

Hypothermia
Hypoventilation
Hyponatraemia
HF
Confusion
Coma

Question 7

Signs of Hypothyroidism one examination

Answer 7

Hands: bradycardia, cold
Head/neck/skin: pale and puffy face, goitre, oedema, hair loss, dry skin, vitiligo
Chest: pericardial or pleural effusion
Abdomen: ascites
Neuro: slow relaxation of reflexes, signs of Carpal tunnel syndrome

Question 8

Investigations for Hypothyroidism

Answer 8

TFTs: T4 depressed, TSH raised (primary), depressed/normal (secondary)

FBC: Mild normocytic anaemia
U+Es: may be decreased
Cholesterol: often elevated
Glucose: may be elevated
CK: may be elevated

Pituitary function + visual field testing: normal (primary), may show tumour (Secondary)

Question 9

Management for Hypothyroidism

Answer 9

Levothyroxine sodium (25-500 micrograms/day PO)
Use TSH to guide (use fT4 in secondary)

Question 10

How is a myxoedema coma managed

Answer 10

1. Oxygen
2. Rewarming
3. Rehydration
4. IV T4/T3 liothyronine sodium -> levothyroxine
5. IV hydrocortisone

Question 11

Complications of Hypothyroidism

Answer 11

Myxoedema coma
Myxoedema madness (psychosis + delusions + hallucinations/dementia
Angina or AF
Osteoporosis 
Resistant hypothyroidism
Pregnancy complications

Question 12

Prognosis for Hypothyroidism

Answer 12

Lifetime therapy required
Generally excellent prognosis with full recovery if treated
Myxoedema coma has mortality of up to 80%