Current issues in the treatment of thyrotoxicosis

Overt thyrotoxicosis is defined as elevated serum free thyroxine (FT4) and free triiodothyronine (FT3), and suppressed thyrotropin (TSH) concentrations. Thyrotoxicosis with TSH suppression only (TTSO), and normal thyroid hormone concentrations, is also defined as mild thyrotoxicosis. Both overt thyrotoxicosis and TTSO may be caused by the same thyroid disorders. The most common cause of thyrotoxicosis is the use of excessive doses of L-thyroxine for the treatment of hypothyroidism, non-toxic goiter or thyroid carcinoma (exogenous thyrotoxicosis). Less commonly, the cause of thyrotoxicosis is endogenous. The endogenous thyrotoxicosis may be due to either overproduction and release of thyroid hormones from the gland with normal/high 24-hour thyroid radioiodine uptake (e.g., Graves disease and toxic nodular goiter), or release of excess thyroid hormones due to follicle disruption with low/absent 24-hour thyroid radioiodine uptake (e.g., sub-acute de Quervain thyroiditis). The present report briefly reviews the current problems regarding the clinical and therapeutical approach to thyrotoxicosis, and in particular the TTSO.