Which hormone would be elevated in the blood in medullary carcinoma of the thyroid?

Which hormone would be elevated in the blood in medullary carcinoma of the thyroid?

• A. Calcitonin
• B. Thyroxine
• C. Catecholamines
• D. Secretin

Answer: (A)

Medullary thyroid carcinoma arises from the thyroid’s parafollicular C cells, which normally secrete calcitonin. Because the tumor originates from these cells, it often secretes excess calcitonin into the blood, making calcitonin the hormone that would be elevated. Elevated calcitonin serves as a useful tumor marker for diagnosis and monitoring of this cancer. The other substances aren’t produced by C cells: thyroxine comes from follicular thyroid cells, catecholamines come from the adrenal medulla, and secretin is produced in the gut, so they aren’t expected to be elevated in medullary thyroid carcinoma.

Medullary thyroid carcinoma arises from the thyroid’s parafollicular C cells, which normally secrete calcitonin. Because the tumor originates from these cells, it often secretes excess calcitonin into the blood, making calcitonin the hormone that would be elevated. Elevated calcitonin serves as a useful tumor marker for diagnosis and monitoring of this cancer. The other substances aren’t produced by C cells: thyroxine comes from follicular thyroid cells, catecholamines come from the adrenal medulla, and secretin is produced in the gut, so they aren’t expected to be elevated in medullary thyroid carcinoma.