Plasma calcitonin and ACTH responses to lysine vasopressin, calcium and pentagastrin in a patient with medullary thyroid carcinoma associated with Cushing's syndrome.

In a case study of medullary thyroid carcinoma (MTC) associated with Cushing's syndrome, elevated levels of urinary 17-hydroxycorticosteroids, plasma ACTH, cortisol, calcitonin (CT) and somatostatin (GHRIH) were documented. Lysine vasopressin administration further increased the levels of plasma ACTH, cortisol and CT, whereas the administration of calcium and pentagastrin increased only the level of plasma CT. Immunoreactive ACTH, CT and GHRIH were highly concentrated in the tumour tissues. Basal plasma ACTH levels were more progressively increased than plasma CT during the postoperative course when the patient was treated with o,p'-DDD, since the tumour was not completely resected. These findings suggest that the secretion of ACTH and CT from MTC were regulated in a different manner.