Radioiodine Uptake as a Function of Stored Iodine and Thyroglobulin in Thyroid Follicles: In Vitro Quantitative Imaging Approach with Secondary Ion Mass Spectrometry (SIMS) Microscopy in Human Nontoxic Goiter

We studied by an imaging technique, secondary ion mass spectrometry (SIMS) microscopy, the ability of thyroid follicles to pick-up and organify radioiodine (¹²⁵I) according to the amounts of iodine (¹²⁷I) and sulfur previously stored in thyroglobulin (Tg). After incubation with radioiodine in miniorgan culture, the SIMS analysis of 14 fragments from 12 goitrous patients permitted the observation of 3 iodine distribution profiles. In group 1 ¹²⁵I and ¹²⁷I were easily detected by imaging; ¹²⁵I concentration in follicular lumen was 80-fold lower than that of ¹²⁷I. In group 2¹²⁵I images were obtained after long-term exposure and image processing. ¹²⁵I concentration was not measurable while that of ¹²⁷I was about 1.7-fold higher than that observed in group 1. In group 3 it was not possible to detect ¹²⁵I while only traces of ¹²⁷I were detected. This last profile can coexist with profile 1 in the same specimen. Tg sulfur concentration was 2-fold lower in group 3 than in the other 2 groups in which they were almost the same and significantly correlated with those of ¹²⁷I. These data provide new insight into Tg and ¹²⁷I traffic in the development of nonfunctioning goiters.