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

Medullary carcinoma of the thyroid is specifically associated with the production of calcitonin, which is a hormone involved in calcium homeostasis. This form of thyroid cancer arises from the parafollicular C cells (also known as C cells) of the thyroid, which are responsible for the synthesis of calcitonin. The presence of elevated levels of calcitonin in the blood serves as an important diagnostic marker for medullary thyroid carcinoma and is often used to monitor the disease and assess treatment response.

Thyroglobulin is a marker primarily related to thyroid follicular cells and is more associated with differentiated thyroid cancers, such as papillary and follicular thyroid carcinomas, rather than medullary carcinoma. C-ret is a proto-oncogene that can be mutated in medullary carcinoma, but it is not as commonly used as a specific marker in diagnosis as calcitonin. Free T4 is a measure of thyroid hormone activity but is not directly related to the identification or assessment of medullary carcinoma. Therefore, calcitonin is the most specific and clinically relevant marker for this type of thyroid cancer.