Endocrine Abstracts

Introduction: Multiple endocrine neoplasia type 2 (MEN2) is an autosomal dominant disorder with an estimated prevalence of 1 per 30,000 in the general population. MEN2 is subclassified into two distinct syndromes: types 2A (MEN2A) and 2B (MEN2B). MEN2A and 2B are inherited in an autosomal dominant pattern with very high penetrance. In both syndromes, there is an occurrence of multicentric tumour formation in all organs where the RET proto-oncogene is expressed.

Case: We present a 34 years old patient with MEN2B. He is after total thyroidectomy for medullary thyroid cancer (T1bmN1aM0) in 2013. After operation, there was normalisation of calcitonin levels with negative finding on ultrasound of the neck. That’s why he was not indicated for neck lymph node dissection. External beam radiotherapy (60Gy) was provided. According to genetic examination he is a carrier of a germ point heterozygous mutation in the 11th exon of the RET proto-oncogene. During our surveillance there were borderline calcitonin levels with increase after stimulation. 18F-FDG PET/CT was indicated with the finding of FDG accumulation on both adrenal glands. Surprisingly results of metanephrine and normetanephrine were negative at first time (MNP 0.282 nmol/l, normal values 0.06–0.31, NMNP 0.568 nmol/l, normal values 0.1–0.61). At the second time our suspicion was laboratory confirmed (MNP 1.566 nmol/l, NMNP 1.147 nmol/l). After alpha blockade treatment bilateral adrenalectomy was done and diagnosis of bilateral pheochromocytoma was confirmed. After operation glucocorticoid substitution was provided.

Conclusion: Patients with medullary thyroid cancer should have a genetic examination and should be evaluated for possible pheochromocytoma and primary hyperparathyroidism. In our case, at first time, we had false negative laboratory results. Laboratory tests, to exclude pheochromocytoma, should be repeated if there is clinical suspicion.