ABSTRACT
The generation of T3 and rT3 from added nonradioactive T4 in human polymorphonuclear leucocytes was measured. The amounts of the T3 and rT3 generated were estimated by radioimmunoassay in healthy volunteers and patients suffering of thyroidal and nonthyroidal diseases. Under the incubation conditions employed an increase of in vitro generation of T3 and rT3 was observed in suspensions of hyperthyroid patients, while a significant decrease was found when leucocytes from hypothyroid patients were employed. These alterations were apparently due to either the excess or lack of thyroid hormones, respectively, since they could be restored in both cases by specific clinical treatment. Furthermore, the patients suffering from nonthyroidal illnesses showed decreased T3 generating activity in their leucocyte suspensions, while increased amounts of rT3 could be detected in the same test tube. These results showed that the leucocyte incubation system is a suitable method for investigations of the extrathyroidal metabolism of thyroid hormones in humans.
