A 37-year-old woman presents with several episodes of anxiety, sweating, and palpitations. She has a blood pressure of 170/110 mmHg and her pulse is 76 beats per minute. The patient recalls being told that she has a “persistently elevated calcium level.” Physical examination reveals a 3.5-cm nonmobile, hard, nontender thyroid nodule. Laboratory results are significant for elevated calcium and parathyroid hormone levels. A fine-needle aspiration biopsy of the thyroid nodule was performed and shows malignant cells.
Which of the following is most likely to be elevated in this patient?a. Thyroglobulin
Calcitonin. The patient in this question likely has multiple endocrine neoplasia (MEN) type 2A, also known as Sipple syndrome. The combination of parathyroid hyperplasia, symptoms consistent with pheochromocytoma, and a malignant thyroid nodule makes this the correct answer. The thyroid cancer found in MEN type 2A is medullary carcinoma, which produces calcitonin. (A) Thyroglobulin is used by the thyroid gland to produce T4 and T3. Thyroglobulin levels in the blood are also used as a tumor marker, particularly for papillary or follicular thyroid cancer. Thyroglobulin is not produced in anaplastic or medullary thyroid carcinoma. (C) Alkaline Phosphatase is elevated in several different clinical scenarios, including bile duct obstruction, osteoblastic activity resulting in active bone formation (Paget disease of the bone), and secondary hyperparathyroidism (often from decreased gut absorption of calcium from chronic renal disease). Although the patient in this question has parathyroid hyperplasia, her increased calcium levels would establish the diagnosis of primary hyperparathyroidism (rather than secondary hyperparathyroidism in which you would expect decreased calcium levels). (D) Erythrocyte sedimentation rate (ESR) is a nonspecific measurement of inflammation. Patients with subacute thyroiditis can have an elevated ESR, but you would expect an exquisitely tender thyroid.