Dissociation and Association between Calcitonin and Adrenocorticotropin Secretion

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Abstract
It was suggested that immunoreactive ACTH and calcitonin (CT) are present in the same cell type in the normal pituitary gland and in medullary thyroid carcinoma cells. CT or a related peptide may be part of the .gtoreq. 31 K common precursor molecule. In the present study, patients with several disorders of ACTH secretion were investigated. Widely varying plasma ACTH levels were accompanied by normal CT concentrations. This patient group included untreated patients with Cushing''s disease and after treatment with bilateral adrenalectomy and pituitary irradiation, patients with Nelson''s syndrome, patients with untreated congenital adrenal hyperplasia and patients with Cushing''s syndrome due to ectopic ACTH secretion by a pancreatic islet cell carcinoma and a bronchial carcinoid. In 5 patients with untreated Cushing''s disease, lysine vasopressin stimulated ACTH and cortisol secretion but did not affect plasma CT. A simultaneous increase in plasma ACTH and CT after lysine vasopressin was found in a 45 yr old female patient with medullary thyroid carcinoma with Cushing''s syndrome due to ectopic ACTH secretion. Analysis of the plasma of this patient by Sephadex G-50 chromatography revealed the presence of high (> 30,000 dalton) and low (3200 dalton) MW species with CT-like immunoreactivity. By this indirect method of measuring plasma hormone concentrations in patients with disorders in ACTH secretion, no support was found for the concept of a common precursor molecule for CT and ACTH in the pituitary gland, but such a precursor may be present in some patients with medullary thyroid carcinoma.