Causes of thyrotoxicosis

Underlying aetiology Diagnostic features Common causes Graves' disease Thyroid stimulating immunoglobulin (TSI) binds to and stimulates the thyroid Increased thyroid radioactive iodine uptake with diffuse uptake on scan, positive thyroperoxidase antibodies; raised serum thyroid stimulating immunoglobulin; diffuse goitre; ophthalmopathy may be present Toxic adenoma Monoclonal autonomously secreting benign thyroid tumour Normal to increased thyroid radioactive iodine uptake with all uptake in the nodule on scan; thyroperoxidase antibodies absent Toxic multinodular goitre Multiple monoclonal autonomously secreting benign thyroid tumours Normal to increased thyroid radioactive iodine uptake with focal areas of increased and reduced uptake on scan; thyroperoxidase antibodies absent Exogenous thyroid hormone (thyrotoxicosis factitia) Excess exogenous thyroid hormone Low to undetectable thyroid radioactive iodine uptake; low serum thyroperoxidase values Painless postpartum lymphocytic thyroiditis Autoimmune lymphocytic infiltration of thyroid with release of stored thyroid hormone Low to undetectable thyroid radioactive iodine uptake; thyroperoxidase antibodies present; occurs within six months after pregnancy Less common causes Painless sporadic thyroiditis Autoimmune lymphocytic infiltration of thyroid with release of stored thyroid hormone Low to undetectable thyroid radioactive iodine uptake; thyroperoxidase antibodies present Subacute thyroiditis Thyroid inflammation with release of stored thyroid hormone; possibly viral Low to undetectable thyroid radioactive iodine uptake; low titre or absent thyroperoxidase antibodies Iodine induced hyperthyroidism Excess iodine Low to undetectable thyroid radioactive iodine uptake Drug induced thyrotoxicosis (lithium, interferon alfa) Induction of thyroid autoimmunity (Graves' disease) or inflammatory thyroiditis Thyroid radioactive iodine uptake elevated in Graves' disease or low to undetectable in thyroiditis Amiodarone induced thyrotoxicosis Iodine induced hyperthyroidism (type I) or inflammatory thyroiditis (type II) Low to undetectable thyroid radioactive iodine uptake Rare causes Thyroid stimulating hormone (TSH) secreting pituitary adenoma Pituitary adenoma Raised serum thyroid stimulating hormone and -subunit with raised peripheral serum thyroid hormones Gestational thyrotoxicosis Stimulation of thyroid gland thyroid stimulating hormone receptors by human chorionic gonadotrophin Thyroid radioactive iodine uptake contraindicated in pregnancy. First trimester, often in setting of hyperemesis or multiple gestation Molar pregnancy Stimulation of thyroid gland thyroid stimulating hormone receptors by human chorionic gonadotrophin Molar pregnancy Struma ovarii Ovarian teratoma with differentiation primarily into thyroid cells Low to undetectable thyroid radioactive iodine uptake (raised uptake of radioactive iodine in pelvis) Widely metastatic functional follicular thyroid carcinoma Thyroid hormone production by large tumour masses Differentiated thyroid carcinoma with bulky metastases; tumour radioactive iodine uptake visible on whole-body scan