Thyrotoxicosis:

Causes and investigation

Graves' disease accounts for around 50-60% of cases of thyrotoxicosis.

Causes

• Graves' disease
• toxic nodular goitre
• acute phase of subacute (de Quervain's) thyroiditis
• acute phase of post-partum thyroiditis
• acute phase of Hashimoto's thyroiditis (later results in hypothyroidism)
• amiodarone therapy
• contrast
  • rare, more commonly occurs in elderly patients with pre-existing thyroid disease (e.g. multinodular goitre, Graves')
  • patients with existing thyrotoxicosis should not receive iodinated contrast medium
  • administration of iodinated contrast results in a large iodine load to the thyroid → hyperthyroidism developing over 2-12 weeks

Investigation

• TSH down, T4 and T3 up
• thyroid autoantibodies
• other investigations are not routinely done but includes isotope scanning

Toxic Multinodular Goitre

Toxic multinodular goitre describes a thyroid gland that contains a number of autonomously functioning thyroid nodules resulting in hyperthyroidism.

Nuclear scintigraphy reveals patchy uptake.

Thyroid scintigraphy (I-123) shows patch uptake with multiple foci consistent with toxic multinodular goitre - e Image used on license from Radiopaedia