Simultaneous occurrence of Addison'sdisease and thyrotoxicosis

The simultaneous occurrence of Addison'sdisease obscured the clinical findings of hyperthyroidism. The BMR and RBC uptake of I 131 -labeled triiodothyronine also remained normal. The administration of replacement doses of corticosteroids resulted in obvious clinical thyrotoxicosis and elevation of the BMR and RBC uptake of I 131 -labeled triiodothyronine, without altering the initial elevation of PBI, BEI, and 24-hour thyroidal uptake of I 131 .