METASTATIC MEDULLARY THYROID CARCINOMA WITH NORMAL SERUM CALCITONIN LEVELS

ABSTRACT Objective: Medullary thyroid carcinomas (MTCs) originate from parafollicular C cells and produce the hormone calcitonin, which is primarily responsible for the biochemical dysfunction in calcium metabolism seen in MTC. MTCs constitute only about 5 to 7% of thyroid neoplasms. In rare cases, serum calcitonin can be normal or undetectable. Methods: We present the clinical examination and laboratory findings of a patient with MTC and a review of the literature. Results: A female of 65 years was suspected to have MTC after fine-needle aspiration cytology but serum calcitonin was normal. A total thyroidectomy was performed. Histopathology confirmed MTC. During the 9-year follow-up period, she had persistently normal serum calcitonin level despite lymph node metastasis. Conclusion: Raised serum calcitonin is a biochemical hallmark of diagnosis and recurrence of MTC in the post-surgical period. Our patient, however, is a case of MTC with postsurgical recurrence and metastasis but persistently normal calc...