Differential Diagnosis for Elevated Free T3 and Free T4 with Suppressed TSH and Undetectable Thyroglobulin

• Single Most Likely Diagnosis
  • Thyroid Storm or Hyperthyroidism due to Graves' Disease: This condition is characterized by elevated levels of free T3 and free T4, along with a suppressed TSH. The undetectable thyroglobulin levels could be seen in cases where the thyroid gland is overactive and not producing thyroglobulin or in cases of thyroid destruction. However, Graves' disease is a common cause of hyperthyroidism and often presents with elevated thyroid hormones and suppressed TSH.
• Other Likely Diagnoses
  • Toxic Multinodular Goiter: This condition involves the growth of multiple nodules in the thyroid gland that produce thyroid hormones independently of TSH, leading to elevated free T3 and free T4 and suppressed TSH. Undetectable thyroglobulin might not be a typical finding but could occur in certain cases.
  • Thyroiditis (e.g., Subacute or Silent Thyroiditis): Although thyroglobulin levels are often elevated in thyroiditis due to thyroid gland damage, there could be cases where the levels are undetectable, especially if the thyroiditis has led to significant gland destruction or if the thyroglobulin is being rapidly cleared.
• Do Not Miss Diagnoses
  • Metastatic Thyroid Cancer (e.g., Papillary or Follicular Thyroid Cancer): Although rare, metastatic thyroid cancer could potentially cause elevated free T3 and free T4 if the metastases are functioning and producing thyroid hormones. The undetectable thyroglobulin could be misleading, as some thyroid cancers do not produce thyroglobulin or produce it at very low levels.
  • Exogenous Thyroid Hormone Ingestion: Accidental or intentional ingestion of thyroid hormones could lead to elevated free T3 and free T4 and suppressed TSH. This diagnosis is crucial to consider because it has significant implications for treatment and patient safety.
• Rare Diagnoses
  • Struma Ovarii: A rare ovarian tumor that contains thyroid tissue, which can produce thyroid hormones, leading to hyperthyroidism. The undetectable thyroglobulin might be seen if the ovarian tissue does not produce significant amounts of thyroglobulin.
  • Familial Dysalbuminemic Hyperthyroxinemia: A rare genetic condition that affects the binding of thyroid hormones to albumin, leading to elevated free thyroid hormone levels but normal total hormone levels. However, this condition typically does not suppress TSH to the same extent as other causes of hyperthyroidism.