CHANGES IN THYROID-HORMONE METABOLISM IN EXERTIONAL HEAT-STROKE WITH OR WITHOUT ACUTE-RENAL-FAILURE

The effects of exertional heat stroke (ExHS), with or without acute re nal failure (ARF), on thyroid hormone metabolism were investigated. Ei ghteen ExHS patients were recruited and divided into two groups based on the presence or absence of ARF. Eleven age-matched healthy subjects served as a control group. Serum values of T-3, T-4, TSH, free T-4 (F T4), rT(3), and sulfated T-3 (T3S) were measured in these groups durin g the acute and recovery stages of ExHS. Serum T-3, T-4, and FT4 level s were reduced, with reciprocal increases in rT(3) and T3S levels as t he severity of ExHS increased. The following mean levels of thyroid ho rmones mere found (controls vs. ExHS without ARF vs. with ARF): T-3, 1 514 vs. 1164 vs. 393 pmol/L (P < 0.05 each); T-4, 97 vs. 79 vs. 49 nmo l/L (P = NS and P < 0.05, respectively); FT4, 20.5 vs. 19.5 vs. 19.0 p mol/L (P = NS each); rT(3), 371 vs. 617 vs. 805 pmol/L (P < 0.05 and P = NS, respectively); and T3S, 30.1 vs. 34.2 vs. 71.1 pmol/L (P = NS a nd P < 0.05, respectively). The serum TSH levels were not significantl y different among the three groups. Significantly negative correlation s were found between serum creatinine and T-3 (r = -0.75; P < 0.001) a nd T-4 levels (r = -0.65; P < 0.001), whereas no relationship was note d between serum creatinine and rT(3) values (r = 0.11; P > 0.05). In c ontrast, a correlation was observed between serum glutamic pyruvic tra nsaminase and rT(3) (r = 0.45; P < 0.01). Thyroid function tests retur ned to normal after patients recovered. In conclusion, our results sho w that patients suffering hom ExHS, with or without ARF, displayed alt ered serum thyroid function in proportion to the severity of their con dition. No significant changes in serum levels of rT(3) were observed between the two groups, whereas a positive relationship was observed b etween serum rT(3) and serum glutamic pyruvic transaminase values, sug gesting that the changes in serum rT(3) levels were more dependent on extrarenal illness than on renal disease per se. The moderate increase in serum T3S levels found in patients suffering from both ExHS and AR F may represent a decrease in tissue 5'-monodeiodinase activity as fou nd in other nonthyroidal illnesses. A return of serum thyroid function tests to normal values after recovery from ExHS suggests that the low T-3 state may play a protective role to prevent undesirable catabolic effects. Replacement therapy is thus not recommended.