Curriculum · Metabolic and Endocrine and Diabetes Mellitus
Multinodular goitre
What it is
Multinodular goiter is one of the causes of thyrotoxicosis that runs with a high 24-h radioactive iodine uptake, alongside Graves' disease and toxic adenoma; iodine-induced hyperthyroidism and deposits of functioning thyroid cancer metastases run instead with a low 24-h uptake.
How it is diagnosed
The radioactive iodine uptake test sorts the causes of thyrotoxicosis into two lists. Thyrotoxicosis with a high 24-h RAI uptake belongs to Graves' disease, multinodular goiter, or toxic adenoma. Thyrotoxicosis with a low 24-h RAI uptake belongs instead to factitious hyperthyroidism, subacute thyroiditis, ectopic secretion of thyroid hormones, iodine-induced hyperthyroidism, or deposits of functioning thyroid cancer metastases. So a woman with excessive sweating, flushing, tachycardia and nervousness, whose free thyroxine and triiodothyronine are elevated and whose thyroid-stimulating hormone is decreased, but whose radioactive iodine uptake test shows a complete absence of iodine uptake, is not a multinodular goitre. That picture is factitious thyrotoxicosis, the voluntary but concealed intake of an excessive amount of thyroid hormone.