[The metabolism of thyroid hormones in chronic renal insufficiency]

The levels of tri-iodothyronine (T3), free T3 index (FT3I), thyroxine (T4), free T4 index (FT4I), thyrothopine (TSH), reverse T3(rT3), T3 resin uptake (T3U) and thyroxine-binding globulin (TBG) were investigated in 30 conservatively treated euthyrodic kidney patients with varying degrees of disturbance to kidney function. The authors found that the phenomena of the so-called "low T3 syndrome" (low T3 and FT3 while T4 is low to normal and FT4 and TSH are normal) appear not only in patients with advanced chronic renal insufficiency but also in patients who are in the 2nd state of chronic renal insufficiency (serum creatinine 4--8 mg%). The incidence and degree of reduced T3 were equal in both groups of patients. It must however be stressed that, in contrast to other chronic diseases with "low T3 syndrome", the low T3 concentrations in kidney patients are not accompanied by a simultaneous increase in the synthesis of rT3. The high levels detected of the quotients T4/T3 and the normal levels of TBG allow the reduced capacity of thyroxine-binding globulin (TBG) to be ruled out as the cause of the low levels of T3.