An approach to investigation of the changing pattern of plasma cyclic nucleotides and their correlation with thyroid hormone in hyperthyroid patients before and after 131I treatment.

Abstract

Levels of thyroid hormones (T3,T4) in serum and cyclic adenosine 3′, 5′-monophosphate (cAMP) and cyclic guanosine 3′, 5′-monophosphate (cGMP) in plasma were successively determined in 77 patients with hyperthyroidism before and 1, 2, 3, 6 months after131iodine (131I) treatment. Before treatment, the levels of total serum T3, T4 and plasma cAMP of all of the patients were higher than normal, while the level of plasma cGMP was lower than normal (P<0.0l). The patients were divided into 3 groups: A, B, C, according to the clinical features and serum levels of T3, T4 3–6 months after treatment. Group A (18 patients) clinically showed no improvement, T3, T4 still remained higher than normal and cAMP, cGMP revealed no significant change in comparison with the pretreatment state. Group B (45 patients) clinically showed marked improvement, their thyroid toxic symptoms practically subsided, T3, T4 gradually turned to normal and concentration of cAMP and cGMP subsequently reached normal level. Group C (14 patients) presented temporary hypothyroidic features; their level of T3, T4 fell below the normal range, while the concentration of plasma cAMP and cGMP approached the level contrary to the state before treatment. Since the change of T3 and T4 occurred synchronously, the question of whether T3 or T4 exerted an influence on plasma cyclic nucleotides concentration and the interrelationship between thyroid hormones and cyclic nucleotides as well as the significance of plasma cAMP and cGMP in pathogenesis and therapy of hyperthyroidism remains to be further elucidated.