Differential Diagnosis for Recurrent Goiter with High TSH and Normal T4

• Single most likely diagnosis:

  • b. Hypothyroidism: This is the most likely diagnosis given the patient's history of subtotal thyroidectomy and current presentation of high TSH with normal T4 levels. The elevated TSH indicates that the pituitary gland is trying to stimulate the thyroid to produce more thyroid hormones, which is consistent with primary hypothyroidism. The normal T4 level may suggest that the patient is either in a subclinical state of hypothyroidism or that the thyroid is still producing some amount of thyroid hormones, albeit not enough to suppress TSH production.

• Other Likely diagnoses:

  • a. Recurrent thyroid: Recurrence of thyroid tissue can lead to goiter formation. Although less likely than hypothyroidism given the lab values, it's a plausible explanation, especially if the recurrent tissue is not functioning properly.
  • d. Thyroiditis: Chronic thyroiditis could lead to hypothyroidism and goiter. The inflammation of the thyroid gland could impair its function, leading to elevated TSH levels.

• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):

  • c. Malignancy: Although less common, malignancy in the thyroid gland could present with goiter and alterations in thyroid function tests. It's crucial to rule out malignancy, especially in a patient with a history of thyroid surgery, as it could be a cause of recurrent goiter and has significant implications for treatment and prognosis.

• Rare diagnoses:

  • Other rare causes of goiter and hypothyroidism, such as thyroid dysgenesis or infiltrative diseases affecting the thyroid, could be considered but are less likely given the patient's history and presentation. These would typically be explored if more common causes are ruled out.