Hypothyroidism

Keywords: Myxoedema

Causes

Appropriate Tests

 

Thyroid stimulating hormone. Free T4 if pituitary disease is suspected. Monitoring: TSH should be maintained within the reference interval ie, thyroid replacement therapy should not cause TSH suppression (unless history of differentiated thyroid cancer).

Patients should not be tested at less than monthly intervals, especially if the thyroxine dose has been altered, as the half life of thyroxine is approximately one week.

Testing at 6 monthly intervals is usually sufficient.

Patients with a history of thyroid disease should always have TSH performed prior to anaesthesia/surgery.

See also Goitre

Autoimmune

Thyroid Ab.

  • Hashimoto disease

 

De Quervain's

 

Thyroid ablation

 

  • Surgical

If thyroidectomy was performed for differentiated thyroid carcinoma, thyroxine therapy should be adjusted and suppression of TSH levels may be necessary depending on staging.

  • Radioiodine 

 

Iodine deficiency

 

Drug-induced, especially

  • Lithium
  • Iodides (amiodarone)
  • Interferon

 

Post-partum

 

Congenital

Hypothyroidism should be detected on Neonatal screening.

See also Neonatal screening.

  • Pendred syndrome  

 

  • Aplasia/hypoplasia   

Thyroid radioactive iodine uptake studies may be indicated to establish the diagnosis of thyroid aplasia/hypoplasia or to detect ectopic thyroid tissue.

Hypopituitarism

 

Peripheral resistance to thyroid hormone

Thyroid stimulating hormone and Free T4 are both elevated.