Inhibition of T-3 production in levothyroxine-treated female mice by the root extract of Convolvulus pluricaulis

An investigation was made to evaluate the role of Convolvulus pluricaulis r oot extract in the regulation of hyperthyroidism in female mice. Its possib le site of action was also studied. L-Thyroxine treatment for 30 days incre ased serum concentrations of thyroxine (T-4) and triodothyronine (T-3). The activity of hepatic 5'-monodeiodinase (5'-DI) and glucose-6-phosphatase (G -6-Pase) was also enhanced. On the other hand, administration of the plant extract either alone or with L-T-4, decreased serum T-3 concentration and t he activity of hepatic 5'-DI and G-6-phase, without marked alteration in he patic lipid peroxidation, indicating the possible regulation of hyperthyroi dism by the plant extract, It appears that the action of the plant extract on thyroid function is primarily mediated through the inhibition of 5'-DI e nzyme activity.