Plasma corticotrophin releasing hormone, vasopressin, ACTH and Cortisol responses to acute myocardial infarction

OBJECTIVES We assessed the magnitude and duration of the response of hypothalamic-pituitary-adrenal hormones to the stress of myocardial infarction, in the presence and absence of angiotensin converting enzyme inhibitors. In particular, we wished to analyse the interrelationships between peripheral plasma levels of corticotrophin releasing hormone (CRH), vasopressin (AVP) and adrenocorticotrophin (ACTH), and also between ACTH and Cortisol, during a prolonged medical stress. DESIGN All hormones were measured within 6 hours of the onset of an acute myocardial infarction. Patients were randomly allocated to three different study groups according to a double blind procedure. PATIENTS Group 1 (10 patients) received placebo treatment, Group 2 (13 patients) received a maintenance dose of captopril 25 mg three times daily, Group 3 (11 patients) received enalapril 5 mg three times daily. MEASUREMENTS Peptide hormones were measured by radioimmunoassay, and Cortisol by ELISA. Reference ranges for all hormones were obtained from 40 or more volunteers from the electoral roll. RESULTS At the start of the study, mean±SEM plasma AVP (27.9 ± 4.6 pmol/l) was significantly (P<0 001) raised above the mean for the reference range (1.82 ± 0.09 pmol/ I), and 12 patients had values >50 pmol/l. Mean plasma Cortisol (960 ± 89.6 nmol/l) was also raised above the reference range mean (554±28 nmol/l, P<0.001), as was mean plasma CRH (4.97 ± 0.5 pmol/l, reference mean 1.52± 0.09 pmol/l, P<0001). By contrast, mean ACTH (3.88 ± 0.66 pmol/l) was significantly less than the reference mean (10.7 ± 0.7 pmol/l, P<0.001). During the 72-hour observation period there was a highly significant fall (P<0.001) in plasma CRH, AVP and Cortisol. By contrast, plasma ACTH rose, and the change with time of ACTH was significantly different from the fall in plasma CRH, AVP or Cortisol (P<0.001 for each comparison). No significant differences in plasma CRH, AVP, ACTH or Cortisol responses to placebo, captopril or enalapril were observed. CONCLUSIONS Within 6 hours of a myocardial infarction, mean plasma CRH, AVP and Cortisol values were very significantly raised above mean control values, while ACTH was very significantly reduced. During the 3 days following an acute myocardial infarction, plasma CRH, AVP and Cortisol fell substantially, and this pattern was not influenced by angiotensin converting enzyme inhibitors. By contrast, plasma ACTH showed a significant increase with time. This suggests that the usual relationships between CRH, AVP and ACTH, and between ACTH and Cortisol are disturbed in patients admitted to hospital with myocardial infarction. Maximum levels of AVP observed in 12 patients exceeded 50 pmol/l, which may be sufficiently high to interfere with tissue perfusion. It is postulated that V₁, AVP receptor antagonists may have a therapeutic application in limiting infarct size.