EVALUATION OF THYROXINE (T4) BINDING PROTEINS AND OF THYROID HORMONE: SERUM FRACTIONS IN CHILDREN AFTER CAR DIAC SURGERY

Abstract

Non-thyroidal illness was evaluated in 9 children, chronological age 3.88±3.16 y (X̄+SD), before (B), immediately after (I), and 24 and 48 hs after cardiac surgery. Serum levels of T-binding globulin (TBG), and T4-binding prealbumin (TBPA), albumin (ALB), Total T4 and T3 (TT4, TT3), Albound T4 and T3 (ALB-b T4 and T3), free T4 and T3 (by calculation according to the law of mass action) were determined. ALB-b T4 was also measured experimentally in undiluted serum, using labelled T4. Serum TGB and TBPA were significantly lower in B, I, 24 and 48 hs (TBPA only) (261±17.05, 272±70.17, 259±65.47, 374±103, and 3013±625, 2870±493, 3373±1443, 2309±398 nmol/l respectively) than in controls (c)(456±71 and 5999±2226, respectively, p<0.01). Serum TT4 was significantly lower in I, 24 and 48 hs than in C (88.12±20, 94.91±29.40, 105.5±34.27 and 149±25 nmol/l respectively, p<0.01). Serum ALB-b T4, either calculated or experimentally measured was not different in patients and C. Serum TT3 was significantly lower in B, I, 24 and 48 hs. than in C(2.12±0.11, 1-50±0.57/ 0.95±0.42, 0.92±0.37 and 3.04±0.61 nmol/l, respectively, p<0.01) as well as free T3 and ALB-b T3 at 24 and 48 hs, compared to C(3.22±1.07, 2.15±0.96, 330±11, 240±85 in patients and 7.37±1.9, 675±178 pmol/L in C, respectively, p<0.01). It is concluded that after cardiac surgery in children, although serum TT4 and TT3 are low, free T4 and ALB-b T4 are normal.