The adenylate cyclase-cyclic AMP-phosphodiesterase system in pathological human thyroid.

The adenylate cyclase-cyclic AMP-phosphodiesterase system of human thyroid tissues adjacent to cold nodules (control), two follicular adenomas, one hyperplastic thyroid and one hyperfunctioning follicular carcinoma have been compared. In the hyperfunctional follicular carcinoma the basal adenylate cyclase is much higher than in control tissue, carcinoma adenylate cyclase does not respond to TSH and prostaglandin E1, whereas it responds normally to fluoride. In the hyperplastic, but hypofunctional thyroid the basal adenylate cyclase is higher than in normal tissue whereas the response to TSH, PGE1, and fluoride is normal. No difference between the follicular adenomas and normal thyroid stimulated and unstimulated adenylate cyclase was observed. Furthermore in various thyroid tissues no changes in the level of cyclic AMP phosphodiesterase was found. Our data indicate a greater change in the synthesis rather than in degradation of cyclic AMP in the human pathological thyroids studied.