Thyroid and Parathyroid Surgery: Nodules, Cancer, and Calcium
Thyroid questions test nodule evaluation, cancer staging, and surgical complications. Know that ultrasound is the first imaging study for thyroid nodules and that fine-needle aspiration is guided by ultrasound features (size, microcalcifications, irregular margins, hypoechogenicity). Understand the Bethesda system for cytology and that papillary thyroid carcinoma is the most common thyroid cancer, spreading via lymphatics; follicular carcinoma spreads hematogenously; medullary carcinoma arises from parafollicular C cells and is associated with MEN2 and elevated calcitonin.
Know the complications of thyroidectomy: recurrent laryngeal nerve injury (hoarseness), external branch of superior laryngeal nerve injury (voice pitch), hypocalcemia from parathyroid injury, and hematoma causing airway compromise. Postoperative hypocalcemia is managed with calcium and vitamin D; check calcium and PTH.
For parathyroid disease, understand primary hyperparathyroidism (elevated calcium, elevated or inappropriately normal PTH), most often from a single adenoma, and that sestamibi scanning and ultrasound localize before focused parathyroidectomy. Secondary hyperparathyroidism occurs in renal failure.
Traps: missing medullary carcinoma (check calcitonin, screen for MEN2); attributing postoperative stridor to edema when a neck hematoma is the cause; and forgetting that follicular lesions often require diagnostic lobectomy because FNA cannot distinguish adenoma from carcinoma.
Rule of thumb: "Papillary spreads to nodes, follicular spreads to bone and lung, medullary spreads to nodes and is hereditary until proven otherwise."
Worked example: A patient with a thyroid nodule and elevated calcitonin should undergo total thyroidectomy and central neck evaluation, with genetic testing for RET mutations.