[Unusually high iodine excretion in hyperthyroidism in an iodine-poor area]

In 27 thyrotoxic patients and in 177 healthy controls from the area of Essen we studied the total urinary iodine excretion. Whereas the iodine excretion was only 43.7 +/- 27.3 mug iodine per g creatine in the controls, the corresponding average value was significantly higher in thyrotoxic patients. It amounted to 193.3 +/- 201.7 mug iodine per g creatinine. This finding can not be explained by selection of patients with autonomous adenomas and contamination with iodine. Possible causes are an increased daily iodine uptake by increased dietary intake or iodine containing drugs that might not be remembered by the patients and increased renal clearance of iodine. Strong evidence for a contamination with iodine is the finding of increased differences between measured and calculated PBI, the latter being derived from T4 (D). The differences averaged in both groups 5.3 and 3.2 mug/100 ml. Our data can not exclude a basedowification of preexisting goiters. This unexpected finding gives rise to corresponding investigations in other thyroid centers.