A 34-year-old man is evaluated for episodic palpitations of 8 months' duration. The palpitations last 5 to 10 minutes and then resolve spontaneously. They are usually associated with sweating and anxiety. Medical history is significant for thyroidectomy for medullary thyroid carcinoma diagnosed at 12 years of age. His father has also undergone thyroidectomy for medullary thyroid cancer. His only medication is levothyroxine.
On physical examination, blood pressure is 164/92 mm Hg, pulse rate is 106/min, and respiration rate is 12/min. Auscultation of the heart reveals a regular tachycardia without murmurs. The remainder of his examination is unremarkable.
Laboratory studies show a 24-hour urine excretion of catecholamines of 310 µg/m2/24 h (1832.1 nmol/m2/24 h) and metanephrines of 3400 µg/24 h (17,238 nmol/24 h).
In addition to the presenting diagnosis, which of the following disorders is this patient most likely to develop?
C. Primary hyperparathyroidism
MKSAP Answer and Critique
The correct answer is C. Primary hyperparathyroidism. This item is available to MKSAP 17 subscribers as item 2 in the Endocrinology & Metabolism section. More information is available online.
This patient is most likely to develop primary hyperparathyroidism. He has symptoms related to catecholamine excess from a pheochromocytoma and has a personal and family history of medullary thyroid cancer. This is typical of multiple endocrine neoplasia type 2A (MEN2A) resulting from a mutation in the RET proto-oncogene. Primary hyperparathyroidism due to multiple gland hyperplasia frequently occurs in patients with MEN2A. Patients with primary hyperparathyroidism may present with symptoms related to hypercalcemia (polydipsia, polyuria, and constipation), or the hyperparathyroidism may be found during an evaluation for osteoporosis or nephrolithiasis. Pheochromocytomas in MEN2A are usually benign and intra-adrenal in location, but can be multiple or bilateral.
Insulinoma and prolactinoma occur in multiple endocrine neoplasia type 1 (MEN1). In MEN1, one mutated allele of the MEN1 gene is usually inherited, and a somatic mutation in the other allele is later acquired and results in the formation of neoplasia. The most common endocrine disorder in MEN1 is primary hyperparathyroidism resulting from one or more parathyroid adenomas.
Neurofibroma is not a clinical feature of MEN2A. Neurofibromas, café-au-lait spots, and pheochromocytoma are among the clinical features of the autosomal dominant disorder neurofibromatosis type 1.
- Medullary thyroid cancer, pheochromocytoma, and primary hyperparathyroidism occur in patients with multiple endocrine neoplasia type 2A (MEN2A).