| Urinary Radioiodine Excretion at 15 Days J day! K _ day! x 10? L qq, day! x 10° ” of 13"/Gay TE 3.7 4.85 7.2 0.050 3.7 4.85 13.8 0.066 17.15 7.2 17.15 13.8 3.7 . 3.7 0.16 | 0.21 On the basis of these calculations the normal range of urinary radioiodine excretion at 15 days was estimated to be 0.05 to 0.2% of the peak thyroid content. The problem outlined above is a practical application of an analytical study on the uptake and excretion of iodine in man which will be described more fully in a UCRL report entitled, "The Dynamics of Iodine in Man."