[Calcium, cGMP and cAMP roles in thyroid regulation (author's transl)]

Cholinergic agents induce an accumulation of cGMP in thyroid tissue and inhibit cAMP accumulation and thyroid hormone secretion resulting from TSH action. The aim of the present work was to determine the respective roles of Ca++ and/or cGMP in these actions. The results show that two complementary mechanisms may be demonstrated: 1) cGMP activates phosphodiesterase activity and cAMP hydrolysis. 2) Independently of cyclic nucleotide concentrations, increased intracytoplasmic Ca++ directly inhibits TSH induced stimulated hormone secretion.