Comparison Evaluation of Pituitary-Thyroid Axis Changes in Patients Underwent Minor and Major Cardiac Surgeries

4 Abstract: Background: During illnesses, some events occur in pituitary-thyroid axis causing a disease state named non-thyroidal illness syndrome (NTIS). The aim of this study was to compare pituitary-thyroid axis changes in children less than 18 years old with minor versus major heart operations. Materials and Method: This study was conducted on 52 patients less than 18 year old who had undergone surgery within a period of 8 months from fall 2010 through spring 2011 in heart center of Yazd, Iran. Three sample specimens were taken from every patient. Every sample was assessed for thyroid hormones.Results: All the patients in the major group and 90% of those in the minor group developed NTIS. The severity of NTIS was different between the two groups(P< 0.001). Average admission days at the hospital ward were also more in the major than the minor group (P= 0.014). The trend of changing in serum TSH level on days after surgery in the major group was significant (P< 0.001), but not in minor group(P = 0.622). The trend changing in serum FT4 level on days after surgery in major group was significant (P = 0.0 47), but not in minor group (P = 0.199). Almost all hormone levels reached normal levels at the 4 post-operative day.Conclusion: In major surgery, TSH and FT4 levels drop th significantly after the operation and this makes diagnosis a real challenge, therefore treatment is based mainly on clinical grounds. In minor surgery, the changes in TSH and FT4 levels were not significant after the operation, so we recommend using laboratory tests to diagnose hypothyroidism after operations.