TY - JOUR T1 - TRiiodothyronine levels-reply AU - Wortsman J, Soler NG Y1 - 1979/11/01 N1 - 10.1001/archinte.1979.03630480091042 JO - Archives of Internal Medicine SP - 1320 EP - 1320 VL - 139 IS - 11 N2 - In Reply.—  My co-workers and I agree with Hydovitz et al regarding the uncertainty associated with the use of total T3 (radioimmunoassay) for predicting the outcome of sodium iodide I 131 therapy in hyperthyroidism. Our study was actually prompted by the suggestion that the isolated increase in the level of T3 would be an early marker of recurrence of the hyperthyroidism. Prolonged follow-ups and repetition of the determinations did not bear this out.Our report did not address the question of the mechanism for the increase in the T3 levels. Calculation of the free hormone levels would be an obvious step in that direction; better yet is the direct determination of free thyroid hormone. Nevertheless, there are also pitfalls in this determination, such as interference by free fatty acids,1 and possibly by triglycerides (I. J. Chopra, J. Wortsman, N. G. Soler, unpublished data, March 1978). Even SN - 0003-9926 M3 - doi: 10.1001/archinte.1979.03630480091042 UR - http://dx.doi.org/10.1001/archinte.1979.03630480091042 ER -