Hypothyroidism

Last updated: Tuesday, 14, December, 2010
CausesAppropriate Tests

Thyroid stimulating hormone (TSH). Thyroxine (free) if pituitary disease is suspected. Monitoring: TSH should be maintained within the reference interval ie, thyroid replacement therapy should not cause TSH suppression.

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  antibodies.

  • Hashimoto disease

De Quervain's

Thyroid ablation

  • Surgical 

If thyroidectomy was performed for thyroid carcinoma, thyroxine therapy should be adjusted to cause suppression of TSH levels.

  • Radioiodine 

Iodine deficiency

Drug-induced, especially

  • Lithium
  • Iodides (amiodarone)

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

TSH and thyroxine (free) are both elevated.