Which of the following best describes the embryological basis of the pyramidal lobe of the thyroid and its clinical relevance during thyroidectomy?
- A Remnant of the thyroglossal duct ascending from the isthmus; must be excised in Graves disease to reduce recurrence ✓
- B Remnant of the third pharyngeal arch; must be preserved to prevent Horner's syndrome
- C Ectopic thyroid tissue in the posterior mediastinum; detected on MIBI scan
- D Derived from the ultimobranchial body; contains C-cells at increased risk of medullary carcinoma
Correct answer: A. Remnant of the thyroglossal duct ascending from the isthmus; must be excised in Graves disease to reduce recurrence
Explanation
The pyramidal lobe is a rostral extension of thyroid tissue representing the inferior end of the thyroglossal duct tract, present in approximately 50–80% of individuals, ascending from the isthmus (or left lobe) toward the hyoid bone. In Graves disease and thyroid malignancy, the pyramidal lobe must be actively identified and excised during total thyroidectomy to prevent recurrence or remnant function. Failure to remove it is a recognized cause of persistent hyperthyroidism post-operatively. The ultimobranchial body gives rise to parafollicular C-cells.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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