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Changes in growth hormone and insulin-like growth factor-I levels in the acute stage after open heart surgery and at the time of discharge.

INTRODUCTION
Stress conditions are known to disturb the axis of growth hormone (GH)/insulin-like growth factor-I (IGF-I), but there is little data on this topic after open heart surgery. This study aimed to investigate changes in GH/IGF-I axis in adults undergoing open heart surgery.


METHODS
A total of 162 adult patients admitted for elective major cardiac surgery were studied in a prospective setting. Serum concentrations of GH and IGF-I were measured at four time points: before operation as a baseline, 4 and 12 hours after operation in ICU, and at the time of discharge. Two to 4 venous blood samples were obtained from each patient. To study the changes of GH and IGF-I levels over time, general linear model for repeated measures was applied.


RESULTS
Mean age of patients was 51.2+/-14.3 years. Compared with preoperative values (median 0.8, range 0.05-19.4 ng/mL), GH levels rose significantly at four (median 3.3, range 0.1-55 ng/mL) and twelve hours after surgery (median 5.45, range 0.55-61.2 ng/mL), and continued to remain high at the time of discharge (median 2.1, range 0.02-22.7 ng/mL) (p<0.05). Conversely, compared with preoperative levels (173.5+/-89.9 ng/mL), IGF-I decreased at four (140.9+/-66.9 ng/mL) and twelve hours after operation (135.9+/-59.9 ng/mL) and reached its nadir on the day of discharge (114.8+/-43.8 ng/mL) (p<0.01). The patterns of changes in GH and IGF-I over time were significantly different (p<0.01).


CONCLUSION
Adult patients undergoing open heart surgery go through a state of GH resistance characterized by elevated GH and decreased IGF-I levels from the initial hours after operation.