Anterior pituitary response to thyrotrophin-releasing hormone during open-heart surgery

The anterior pituitary response to thyrotrophin-releasing hormone has been studied in 20 patients submitted to elective open-heart surgical procedures, and in six control patients submitted to closed mitral valvotomy. Standard non-pulsatile normothermic perfusion was used in all the open-heart cases. 400 microgram thyrotropin-releasing hormone was administered by intravenous injection during bypass, at 30 min post-bypass, and at 60 min post-bypass. The same dose (400 microgram) was given during closed mitral valvotomy (Control Group). Thyrotrophin-releasing hormone administration during bypass failed to produce a normal response from the anterior pituitary, in contrast to the normal response pattern seen in the control group (P less than 0.01). Thyrotrophin-releasing hormone given after the period of bypass produced responses within the normal range in the majority of patients. These results suggest that anterior pituitary hypofunction may exist during the period of extracorporeal circulation using non-pulsatile perfusion and that recovery of pituitary function is evident within the first hour post-extracorporeal circulation.