Medullary carcinoma of the thyroid is associated with which specific marker?

Medullary carcinoma of the thyroid is a type of thyroid cancer that originates from the parafollicular C cells, which are responsible for producing calcitonin. The presence of elevated levels of calcitonin in the blood is a hallmark of this type of cancer and is often used as a tumor marker in diagnosis and monitoring. Patients with medullary thyroid carcinoma may have significantly increased levels of calcitonin, which can aid in both confirming the diagnosis and assessing the effectiveness of treatment over time.

The other options are indeed important in different contexts regarding thyroid health. Thyroglobulin is primarily associated with differentiated thyroid carcinoma (such as papillary and follicular types) and serves as a tumor marker for those cancers. Free T4 is a measure of thyroid hormone levels in the body but is not specifically indicative of medullary carcinoma or its behavior. C-retail is likely a typographical error, but if it were intended to refer to RET (the proto-oncogene), while mutations in the RET gene are indeed associated with medullary thyroid carcinoma and hereditary syndromes, it is not a direct marker in the same clinical sense as calcitonin.

Thus, calcitonin stands out as the specific marker associated with medullary