Separation of autonomous function from cell density in non-immunogenic hyperthyroidism--II. quantified comparison before and after radioiodine therapy.

Regional autonomous cell mass (Q: cell density ratio) and function (T: toxicity index) were compared by double isotope parametric thyroid scintigraphy (Als et al., Nucl. Med. 1995; 34) in 53 patients with non-immunogenic hyperthyroidism before and after radioiodine therapy (aRIT) and showed a break-down (medians) of Q: 4.3-->1.0 (toxic adenomas: TA), 2-->1.1 (multifocal functional autonomies: MFA)(p < 0.0001) as of T: 96-->1.7 (TA), 15-->1.1 (MFA) (p < 0.001). Five functional aRIT patterns resulted: euthyroidism (n = 37, 70%), at half with scarred/non-scarred autonomous areas (low/higher T, respectively), primary hypothyroidism (n = 4), residual hyperthyroidism (n = 7), secondary hyperthyroidism (n = 5). The last two groups with persistent subnormal TSH values were clearly separated by divergent T, thyroxine and triiodothyronine levels. A resulting T > 1 may represent a clinically sub-critical mass of residual autonomous tissue. This new technique facilitates individual pretherapeutic evaluations and aRIT quality control.