Hypothyroidism

Question 1

Hypothyroidism Definition

Answer 1

Hypothyroidism is the clinical state arising from decreased production of or functionally decreased thyroid hormones

Question 2

Hypothyroidism Aetiology

Answer 2

• Autoimmune
  * Primary atrophic hypothyroidism
  * Hashimoto’s Thyroiditis
  * Both commonly seen with other autoimmune disorders
  * DM1, Addison’s & PA
  • Post-thyroidectomy or Radioiodine treatment
  • Drug induced
  • Iodine deficiency
    
    • Endemic goitre is the most common worldwide cause of hypothyroidism
  • Subacute thyroiditis
    
    • Temporary hypothyroidism after hyperthyroid phase
  • Secondary hypothyroidism
    
    • Hypopituitarism

Question 3

Define Primary Atrophic Hypothyroidism

Answer 3

• Common

* Diffuse lymphocytic infiltration of the thyroid leading to atrophy, hence no goitre

Question 4

Define Hashimoto’s Thyroiditis

Answer 4

• Goitre due to lymphocytic and plasma cell infiltration.
• More common in women 60-70 y.o.
• Can be hypothyroid or euthyroid
• Rarely initial period of hyperthyroid
• Very high autoantibody titres

In Hashimoto’s thyroiditis there are widespread chronic inflammatory changes that include lymphocytes, plasma cells and macrophages. Infiltrate replaces the normal thyroid tissue. The follicles are small and atrophic

• Residual thyroid follicles are lined by eosinophilic Hurtle cells
• Dense lymphocytic infiltrate

Question 5

Drug Induced Causes of Hypothyroidism

Answer 5

• Antithyroid drugs
  * Amiodarone
  * Lithium
  * Iodine

Question 6

Hypothyroidism Clinical Presentation

Answer 6

• Cold intolerance
  
  • Dry skin
  • Alopecia
  • Bradycardia
  • Weight gain
  • Hypoactivity - mentally slow, depression
  • Decreased stool frequency/constipation
  • Menorrhagia (heavy periods)
  • Reduced libido
  • Slow reflexes

Question 7

Hypothyroidism Pregnancy Complications

Answer 7

• Eclampsia
  
  • Anaemia
  • Prematurity
  • Decreased birthweight
  • Stillbirth
  • Postpartum Haemorrhage (PPH)

Question 8

Hypothyroidism Investigations

Answer 8

• Thyroid function tests
  
  • Thyroid autoantibodies
  • Cortisol
    
    • To exclude Addison’s disease (adrenal insufficiency)
  • ECG
    
    • Bradycardia

Question 9

TFTs to Differentiate Primary and Secondary

Answer 9

TSH
- Primary - Increase
- Secondary - Decrease
T4
- Primary & Secondary - Decrease
T3
- Primary & Secondary - Decrease / No change

Question 10

Thyroid autoantibodies investigated for

Answer 10

• Anti-Thyroid Peroxidase (Anti-TPO) and Anti-Thyroglobulin Antibodies (ATA)
  * Suggest autoimmune aetiology
  
  • Anti-TPO
    
    • Suggests Hashimoto (90%)

Question 11

Hypothyroidism Management

Answer 11

Treatment is straightforward, replacement thyroid hormone is to be given
Replacement - Thyroxine

Question 12

Myxoedema Coma Overview

Answer 12

Occurs in those with longstanding hypothyroidism. After a time there are adaptions such as peripheral vasoconstriction to maintain core body temperature. Myxoedema coma is a kind of decompensated hypothyroidism in which homeostasis is overwhelmed by hypothermia, infection or some medications (amiodarone).

Question 13

Myxoedema Coma Clinical Presentation

Answer 13

• Impaired consciousness
• Hypoventilation
• Hypothermia

Question 14

Myxoedema Coma Management

Answer 14

• Liothyronine
  * Intravenous thyroxine is used due to rapid onset and possible impairment of oral absorption (pseudo-ileus) in hypothyroidism