Radioiodine retention by 2 Japanese male adults after a single oral dose.

A dose of 2.74 kBq of carrier-free 131I (NaI) was given orally to 2 male adults (A and B) in their routine works under a limitation of iodine intake for A and a fairly free access to iodine intake for B for 2 weeks predose. In both the thyroid and the whole-body, the retentions were expressed with a 2 term-exponential function. The metabolic data for subjects A and B are as follows: (1) a peak thyroidal uptake; 28.9 and 10.3% at 24 hours postdose (2) an effective half-time in the thyroid; 6.4 and 6.1 days (3) an effective half-time in the thighs; 0.2 and 0.3 day (4) excretion of 131I in the first 24-hr urine; 72 and 88% of the given dose (5) an amount of stable iodine in 24-hr urine before 131I administration; 0.29 and 2.0 to 5.4 mg. The dose commitments were estimated 1.19 and 0.39 mGy to the thyroid and 1 and 0.5 μGy to the total body for subjects A and B, respectively. The same results were obtained using the “S”, by MIRD.