Is the low tri-iodothyronine state a crucial factor in determining the outcome of coronary artery bypass patients? Evidence from a clinical pilot study.
The cardiovascular system is an important target for thyroid hormones. The present study evaluates the changes affecting thyroid hormone metabolism during and 6 days after coronary artery bypass and their relationship with the post-operative outcome of the patients. Thirty-three patients were enrolled in the study; their thyroid hormone profiles were determined at 13 sampling points during surgery and for 6 days afterwards. Serum total tri-iodothyronine (T3) and free T3 (FT3) concentrations decreased significantly after surgery (P<0.001) and they remained significantly low until the end of the study. Free thyroxine (FT4) and T4 declined significantly immediately after surgery (P<0.05 for FT4, P<0.001 for T4) but they returned to baseline values (24 h and 96 h post-surgery respectively). Serum reverse T3 increased remarkably 36 h after surgery (P<0.001) and remained significantly higher than the baseline value throughout the study. A relevant finding was that the days of post-operative hospitalization (10+/-3 days, means+/-S.D.) was inversely correlated with the slope of the recovery of T3 concentration (P<0.001) or with the area under the plasma curves of T3 (P=0.024, time range 72-144 h) and the FT3/FT4 ratio (P=0.037, time range 72-144 h) during the post-operative period. Our data suggest a prolonged reduction of T4 to T3 conversion in patients undergoing cardiac surgery and indicate that the recovery period is the most critical in the evaluation of a possibly successful approach for T3 substitutive therapy.
Sabatino
L
L
Institute of Clinical Physiology, National Council of Research (CNR), Via Moruzzi 1, San Cataldo, 56124 Pisa, Italy. lauretta@ifc.cnr.it
Cerillo
A G
AG
Ripoli
A
A
Pilo
A
A
Glauber
M
M
Iervasi
G
G
D000368:Aged; D000704:Analysis of Variance; D019540:Area Under Curve; D001798:Blood Proteins / Q000032:analysis; D001026:Coronary Artery Bypass; D003327:Coronary Disease / Q000097:blood* / Q000601:surgery*; D006801:Humans; D008875:Middle Aged; D011184:Postoperative Period; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D016896:Treatment Outcome; D014284:Triiodothyronine / Q000097:blood*; D014285:Triiodothyronine, Reverse / Q000097:blood
D001798:Blood Proteins; D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse; D013972:Thyrotropin; D013974:Thyroxine