Author`s Reply.

To the Editor,

We have read with interest the letter to the editor related to our article “Nonthyroidal illness syndrome in off-pump coronary artery bypass surgery” published in Anatolian Journal of Cardiology 2015: 15: 836-42 (1) and the questions within. We appreciate the authors’ interest in our subject of investigation. They raise an interesting question about the effects of duration of cardiopulmonary bypass (CPB) and aortic cross-clamping time (AXC) during cardiac surgery on neuro-humoral mechanisms and, therefore, possibly on thyroid function as well. Of course, the longer the operation lasts, and the longer the CPB and AXC times are, the more we can expect these effects to become evident. In our study, we observed that the CPB time was 69.74±19.26 min and the AXC time was 46.59±12.07 min. We think that with a larger sample and a differently designed study, these effects might be observed and analyzed. It would be interesting to compare sub-groups of patients operated using on-pump coronary bypass surgery technique (ONCAB) regarding the duration of CPB and AXC, as well as sub-groups of patients of different ages, including older patients, and by all means using larger samples. Using the data from our research, we see that CPB time in our study was just a bit longer than that in the study of Velissaris et al. (2), but the AXC time was somewhat (maybe even considerably) longer in our patients. It was therefore our conclusion that the age of our patients was the primary key as to the percentage of them having experienced non-thyroidal illness syndrome (NTIS) after cardiac surgery in comparison to other investigators’ papers on this subject. We have stated some study limitations in our paper: a larger sample with more details and parameters investigated and analyzed, as well as a sample with a wider age range, might reveal additional information about this interesting phenomenon.