These most commonly due to Graves disease, but can be caused by inflammation or a multinodular goitre.

This accounts for the multinodular goitre appearance.

Symptoms of toxic multinodular goitre are similar to that of hyperthyroidism, including:

Toxic multinodular goitre High blood levels of thyroid hormones (most accurately termed hyperthyroxinemia) can occur for a number of other reasons:

A "diffuse goitre" is a goitre that has spread through all of the thyroid (and can be a "simple goitre", or a "multinodular goitre").

Plummer's disease is named after the American physician Henry Stanley Plummer but refers to a single toxic nodule (adenoma) which may present with the background of a suppressed multinodular goitre.

A common outcome following radioiodine is a swing from hyperthyroidism to the easily treatable hypothyroidism, which occurs in 78% of those treated for Graves' thyrotoxicosis and in 40% of those with toxic multinodular goitre or solitary toxic adenoma.

Also seen, if the patient is hyperthyroid, (i.e., has too much thryoid hormone) are more general manifestations, which are due to hyperthyroidism itself and which may be seen in any conditions that cause hyperthyroidism (such as toxic multinodular goitre or even thyroid poisoning).