Nuclear thyroxine binding in human mononuclear blood cells from hyperthyroid and hypothyroid patients before and after treatment.

Nuclear binding of [125I]T4 in human mononuclear blood cells was examined in six hyperthyroid and six hypothyroid patients before and after treatment. In hypothyroid patients the nuclear T4 binding was initially increased and subsequently normalized as the patients became euthyroid suggesting a homeostatic counter-regulation. The thyroid state did not affect the nuclear T4 binding in hyperthyroid patients. Treatment with methimazol however increased the nuclear T4 binding, suggesting either a direct effect of methimazol on the hormone-receptor interaction or that the patients had become slightly hypothyroid during the treatment. The TSH was shown not to affect nuclear T4 binding. The thyroid state of the patients did not significantly affect the nuclear accumulation of the T3 produced intracellularly by deiodination of T4.