Differential Diagnosis for Recurrent Goiter with High TSH and Normal T4

• Single most likely diagnosis
  • Hypothyroidism: This is the most likely diagnosis given the patient's history of subtotal thyroidectomy and the laboratory findings of high TSH with normal T4. The high 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 indicate that the patient is on thyroid hormone replacement therapy or that the thyroid gland is still producing some amount of thyroid hormones, albeit not enough to meet the body's needs.
• Other Likely diagnoses
  • Recurrent thyroid: Recurrence of thyroid tissue can occur after subtotal thyroidectomy, leading to the formation of a goiter. However, this would not typically cause high TSH levels unless the recurrent tissue is not functioning properly.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Malignancy: Although less likely, malignancy in the thyroid gland or in the recurrent goiter should not be missed, as it can have serious consequences if left untreated. The presence of a goiter and a history of thyroid surgery could potentially be associated with an increased risk of thyroid cancer.
• Rare diagnoses
  • Thyroiditis: This is an inflammation of the thyroid gland, which can cause goiter and alterations in thyroid function tests. However, it is less likely in this scenario given the patient's history and the specific laboratory findings. Thyroiditis can sometimes cause transient hyperthyroidism followed by hypothyroidism, but the presentation with high TSH and normal T4 is more suggestive of hypothyroidism rather than an acute inflammatory process.