Triiodothyronine (T3) reflects renal graft function after renal transplantation

OBJECTIVEAbnormalities in thyroid function are observed in patients with end stage renal disease. However, there are no data available evaluating sequential changes of thyroid function after renal transplantation. Therefore, we have studied thyroid hormone function in the immediate post‐operative period after renal transplantation in order to determine the relationship between improving renal function and changes in thyroid hormone economy. DESIGN AND PATIENTSThyroid function was evaluated in 22 patients before and on days 1, 3, 7 and 15 after renal transplantation. All patients received prednisone and cyclosporin as immunosuppressive therapy. Twelve patients with normal renal function undergoing comparable surgical procedures served as a control group. MEASUREMENTSSerum creatinine and thyroid hormone parameters (total T4, total T3, free T4, free T3, Thyroxin binding globulin (TBG), reverse T3, T3 sulphate and TSH) were measured. RESULTSAccording to post‐operative kidney function after renal transplantation, patients could be subdivided into three groups: five patients had primary graft function (group I); seven patients had delayed graft function because of acute renal failure (group II); 10 patients had delayed graft function requiring high doses of prednisone and some also of OKT3 because of acute rejection (group III). There was a significant fall in T3 and T4 concentrations with a concomitant rise in reverse T3 in all patients up to 3 days after renal transplantation. However, only patients in group I reached pre‐operative values on day 15 after renal transplantation (serum creatinine 167±52 μ m ), whereas patients in group II (creatinine 609±118 μ m ) and group III (creatinine 839±71 μ m ) continued to have T3 concentrations well in the hypothyroid range (group I, 1.68±0.28 n m ) vs 0.87 ± 0.09 n m in group II and 0.76 ± 0.10 n m in group III; P <0.01). Serum T4 concentrations were also low in group III (47.7 n m vs 100.2 n m in group I; P <0.05) 15 days after renal transplantation. These changes were accompanied by a concomitant fall in T3/TBG ratio and in free T3. Elevated reverse T3 returned to normal values in all groups on the 15th day after renal transplantation. TSH fell significantly on the first post‐operative day, but did not return to pre‐operative values in renal transplantation patients. In the control group, TSH did not change during the study period. T3 sulphate, known to be elevated in chronic renal failure, remained above normal in all patients irrespective of graft function during this study period. CONCLUSIONST3 concentrations reflect renal graft function after renal transplantation. T3 is below normal in patients with delayed graft function (acute renal failure or acute rejection). The post‐operative period (up to 3 days after renal transplantation) is associated with a low T3 syndrome. TSH does not return to pre‐operative values even in patients with primary graft function. This might be due to the administration of prednisone. T3‐sulphate is elevated before and after renal transplantation irrespective of graft function.