Concomitant secretion of calcitonin, beta-endorphin and ACTH from medullary thyroid carcinoma in vivo and in vitro.

The present study was performed to investigate the possible synthesis of a common precursor molecule for calcitonin (CT), adrenocporticotropin (ACTH) and beta-lipotropin (beta-LPH)/ beta-endorphin (beta-EP) by the human medullary thyroid carcinoma (MTC). In a patient with MTC but without Cushing's syndrome, the response of plasma CT, ACTH and cortisol levels to a calcium infusion, lysine vasopressin (LVP) and dexamethasone were measured. A parallel increase of these hormones in response to calcium and LVP was seen, while there was a paradoxical increase of CT during dexamethasone infusion. Incubation of MTC fragments obtained at surgery showed a significant correlation of the secretion of CT, ACTH and beta-LPH/ beta-EP in response to calcium, LVP and dexamethasone. The concomitant release of these hormones in vivo and in vitro could be compatible with the synthesis of a common precursor molecule for CT, ACTH and beta-LPH/ beta-EP in MTC, although this was not substantiated by gel-chromatography of the tumor extract. Corticotropin releasing factor, a regulator of the normal processing of pro-opiococorticoid precursor molecule in the anterior pituitary gland, is also able to activate ACTH, beta-LPH/ beta-EP and calcitonin secretion from the malignant C-cell of the thyroid.