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Compartmental analysis was applied to simultaneously acquired 132-I-iodide and 99mTc-pertechnetate thyroid uptake data. The method allowed for arterio/venous differences in plasma tracer level and for an 'instantaneous' phase of thyroid uptake. Observations in four thyrotoxic patients, before and during antithyroid drug therapy, revealed greater 'instantaneous' uptake of TcO4-. The results also revealed that 'instantaneous' uptake of both I- and TcO4- may increase over the first six months of drug therapy. These findings could not be explained by the estimates of unidirectional clearance which were greater for I- and varied little during the early stages of drug therapy.

The concentration of iodide (I(-)) and pertechnetate (TcO(4) (-)) and bromide (Br(-)) has been measured simultaneously in gastric juice and parotid saliva. The combined gastric and salivary clearance for iodide and pertechnetate is more than twice the clearance of these ions by the thyroid gland. The concentration of the ions was in the order I(-)>TcO(4) (-)>Br(-) in both gastric juice and saliva. Differences exist between the secretion of iodide, pertechnetate, and bromide. Bromide, in contrast to iodide and pertechnetate, was found to be more concentrated in gastric juice than in saliva. The ratio of the iodide to pertechnetate clearance was greater in gastric juice than in saliva.