Differential Diagnosis for Recurrent Toxic Multinodular Goiter (MNG) after Near Total Thyroidectomy

• Single most likely diagnosis:
  • D. Autonomous nodule: This is the most likely diagnosis because an autonomous nodule can produce thyroid hormones independently of TSH stimulation, leading to hyperthyroidism (low TSH, high T3, and potentially normal T4 if the nodule primarily produces T3). The recurrence after surgery suggests that the autonomous nodule was not completely removed or that new nodules have developed with autonomous function.
• Other Likely diagnoses:
  • B. Hyperthyroidism: This is a broad category that includes several conditions, but given the context, it's likely referring to the recurrence of hyperthyroidism due to the toxic MNG. The lab values support hyperthyroidism, but the specific cause (e.g., autonomous nodule, diffuse toxic goiter) needs to be determined.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
  • C. Suppression T Cell: Although less common, certain immune system dysregulations could potentially lead to abnormal TSH suppression. However, this would be an unusual cause of the described lab findings and clinical scenario.
• Rare diagnoses:
  • A. Hypothyroidism: Given the lab values (low TSH, high T3, normal T4), hypothyroidism is unlikely as it typically presents with high TSH and low T3 and T4 levels. However, in some rare cases of hypothyroidism, especially if there's a mix of thyroid hormone resistance and thyroiditis, or other complex thyroid disorders, the presentation could be atypical. But this would not typically cause the described pattern of low TSH with elevated T3.

Note: The provided lab values and clinical history strongly suggest a diagnosis related to hyperthyroidism rather than hypothyroidism. The focus should be on identifying the cause of hyperthyroidism, with an autonomous nodule being a leading candidate given the history of toxic MNG and recurrence after surgery.