Evidence of iodine storage within thyroid stroma after iodine treatment: imaging by secondary ion mass spectometry (SIMS) microscopy in goitrous tissue

We measured the 127I distribution within tyroid tissue to find out where intrathyroid iodine was deposited during iodine treatment in eight Tunisian female patients (aged 33-58 yr) with endemic euthyroid goiter. Before surgery, five patients were treated during 6 months either by Lugol's solution (group 1: three patients) or by Lugol's and L-thyroxine (group 2: two patients). All patients remained euthyroid during the course of the treatment, which supplied 3.8 mg/day iodine. Three other patients did not receive Lugol's solution (control group). Secondary ion mass spectrometry microscopy was used to map 127-I quantitatively on thyroid sections. Specimens obtained at thyroid surgery were divided macroscopically into nodular and extranodular tissue and chemically fixed to preserve organified iodine. The iodine profile of patients in group 1 did not differ from that in group 2: large amounts of iodine were localized in thyroid follicles and stroma of both nodular and extranodular tissues. In the control group, iodine within stroma was found only in the extranodular tissue. Despite the limited number of patients studied, these data suggest that stromal iodine might represent a storage compartment in times of large iodine supply.