The calcitonin test is used during diagnosis of C-cell hyperplasia and medullary thyroid cancer, evaluation of treatment efficacy, and monitoring for recurrence. It is also for screening of medullary thyroid cancer in those with family members with multiple endocrine neoplasia type 2 (MEN 2).

Excessive calcitonin is produced in the rare conditions of C-cell hyperplasia and medullary thyroid cancer. C-cell hyperplasiam, a benign condition, may or may not progress to become medullary thyroid cancer. Medullary thyroid cancer is malignant – can spread beyond the thyroid and be difficult to treat if not discovered early.