Which thyroid carcinoma is associated with multiple endocrine neoplasia and has increased levels of calcitonin?

Medullary carcinoma is the type of thyroid cancer that is closely associated with multiple endocrine neoplasia (MEN) syndromes, particularly MEN type 2A and 2B. This type of carcinoma arises from the parafollicular C cells of the thyroid, which are responsible for producing calcitonin. Patients with medullary carcinoma typically present with elevated levels of calcitonin, which can be utilized as a tumor marker in diagnosis and monitoring of the disease.

The link to multiple endocrine neoplasia is particularly significant because individuals with these syndromes may have not just medullary thyroid carcinoma but also other endocrine tumors, such as pheochromocytoma and primary hyperparathyroidism. The elevated calcitonin levels serve as a characteristic laboratory finding in medullary carcinoma that helps differentiate it from other forms of thyroid malignancies. This is why medullary carcinoma is the correct answer, showcasing its distinct clinical and biochemical profile in relation to thyroid neoplasms and systemic syndromes like MEN.