<prompt> A patient presents with BL proptosis, heat intolerance and palpitations; most unlikely diagnosis here would be -Hoshimotos thyroiditisThyroid adenomaDiffuse thyroid goitreReidels thyroiditis  <response>: Ans. is c i.e., Riedels Thyroiditis As already mentioned above, a patient with Reidels thyroiditis may present with hypothyroidism, but never with hypehyroidism. But one should be aware that thyroid ophthalmopathy is seen mainly in Graves disease and very rarely in any other cause of hypehyroidism. Also know Diff. between hypehyroidism and thyrotoxicosis Thyrotoxicosis is the state of thyroid hormone excess and hypehyroidism means excessive thyroid function. Both are not synonyms, however the major causes of thyrotoxicosis are hypehyroidism caused by Graves disease, toxic multinodular goitre and toxic adenomas. Causes of Thyrotoxicosis Primary hypehyroidism Graves disease Toxic multinodular goitre Toxic adenoma Functioning thyroid carcinoma metastasis Activating mutation of the TSH Receptor - Activating mutation of Gsa McCune-Albright syndrome Struma ovarii thyroid tissue within ovarian tumor Jod-Basedow phenomenon or iodine-induced hypehyroidism : thyrotoxicosis may occur in patients with multinodular goitre, after intake of large amounts of iodine, in the diet or in the form of radiographic contrast material or drugs, especially amiodarone. Thyrotoxicosis without hypehyroidism Subacute thyroiditis - Silent thyroiditis Hashimotos thyroiditis - transient hypehyroidism is seen during the initial destructive phase Other causes of thyroid destruction : amiodarone, radiation, infarction of adenoma Thyrotoxicosis factitia : thyrotoxis due to ingestion of excessive amounts of exogenous thyroid hormone or thyriod tissue Secondary hypehyroidism TSH secreting pituitary adenoma Thyroid hormone resistance syndrome : occasional patients may have features of thyrotoxicosis. Chorionic gonadotropin-secreting tumors Gestational thyrotoxicosis. 