28 devoid of physiological activity. Hence an iodo- protein containing onlythese iodoamino acidsis likely to be-also physiglogically inactive. The reason theseindividuals have such an iodoprotein in the blood is not clear. The data on normal controls from the Eastern United States, who showed 0.80 ug% iodoproteiniodine in their séfum,sug- gest thatit is a normal, albeit minor, constituent. The method.of chromatography employed is such that well under 5% (or 0.2 pge%) of serum thy- roxine iodine appears in the unretardedor iodoprotein fraction. Therefore, the finding of iodoprotein does not appear to be a methodologic artifi More‘recently, with the developmentof thyroid abnormalities in the exposed Marshallese (to be described), it was possible to examine serum iodoprotein levels in cases with thyroid hypofunction. These data are presented in Table 16. It seems likely that the source of the iodoprotein waslargely extrathyroidal, since the levels of iodoprotein were near the normally high Marshallese values (a) in cases which had been on suppressive thyroxine therapy, (b) in cases with atrophic glands due to radiation (subjects No. 3 and No. 5), and (c) in thyroidectomized cases. The source of the iodoprotein is not known. The previously reported finding of high plasma proteins,’ particularly gamma globulins, in the Marshallese is of interest but may be an unrelated phenomenon. It will be important to see in future studies whetherthe iodoprotein can be labeled with radioiodine. The data on urine iodine show values in the normal range. In general, it had been expected that individuals living close to the sea and eating seafood and fish would show relatively higher iodine intake. The inhabitants of the Marshall Islands have fish as one of their main sources of animal protein. Furthermore, these people are constantly exposed to sea spray, since the island at its widest is about '4 mile across, andits highest point is 20 ft above hightide. The data:onprimary iadine were used with the results amount to Thyront. Function J Total No. iodine, -PRI, ug cee es 3° 5S 65 i7a. 7 a: « » age <i De s : t “32 gee B31 L Gi 2 10 aetLB Fis *Phyroidectomized** te ALB <05 2° Iodoprotein T, adine, . ioding,* Hypath¥toid 1, 6 Os =6«<05 2.0 a SRD > (2.2) (1.3) | (1) “ >1.3) (>0.8} ibe: (By 3.2 [4.5] 3.8 [2.9] ence between# suredidirectly by +41Thyroxifft dine secreted daily by the thyroid. Thevalue 76"pg/day is.somewhat hehe the Serum lodopiBtein Lévels in Relation Subject” ed with aEseudiestto calgulate the 3% fag/dayfound Stanbury et'al.** ar g/day ie ‘by Fr Ingbar** butloserto the we 7 dayproposed by Riggs.*’ Unfortuae : Bug is known aboutthe rate of turn- sever ofthe serum iodoprotein.If it hasqnughly the semgrate ofdegradation and the same volumeof ition as thyroxine and it is asaymedgta have in the thyxeid gland, then, Marshallese thymids te ould ex- ANIC portional to the level.eforganic iodine /dditiongf odalippporine vatues ave e levglsfor Marshallese multiplicationof the ratio by ‘Use. best.value. for iodine seca normal ee 2.22+4.53 vac. 0.8043.Tex OSSva/ay. This ns Hhicy welliienthe76-yp/dy lated independently frog rine; studies and is compati with Flinical picture eink +Treated with t-thyroxine, 0.2 mg per day, for 6 months. Values in brackets are determination made prior to starting thyroxine treatment (1965). epasruthypid status of amclevated PBI elevatéd thyroid iodiffésecretion rate. However, as noted above, it seems somewhat morelike- ly that the serum iodoprotein is not of thyroidal origin.