Lack of desensitization of 3',5'-cyclic AMP response to thyrotropin stimulation in differentiated thyroid carcinoma

The course of the cAMP response to thyrotropin (TSH) in 23 specimens of differentiated thyroid carcinoma and the adjacent normal tissue was studied. In the carcinomatous tissue, the cAMP concentration in slices incubated with TSH was significantly greater after 2 h than after 15 min of incubation; the level was almost the same at both times in normal tissue. The effects of an initial exposure of thyroid slices to TSH (50 U/l) on the subsequent cAMP responsiveness to the hormone were investigated in seven more differentiated thyroid carcinomas. In normal tissue, the cAMP level in slices exposed to TSH, washed, and exposed again was lower after the third incubation than in slices exposed to TSH only in the third. In contrast, the cAMP level tended to be greater after the second of 2 TSH incubations in 5 out of the 7 specimens of carcinomatous tissue. The data suggest that differentiated thyroid carcinoma lacks desensitization of the cAMP response to TSH.