BIO-AVAILABLE TESTOSTERONE LEVELS FALL ACUTELY FOLLOWING MYOCARDIAL INFARCTION IN MEN: ASSOCIATION WITH FIBRINOLYTIC FACTORS

Abstract

The effect of acute myocardial infarction on plasma levels of testosterone in men is unclear. No previous studies have evaluated the bio-available fraction of testosterone. Low plasma testosterone levels have been associated with several risk factors for myocardial infarction, including an unfavorable fibrinolytic profile. In a prospective, case control study, we examined changes in plasma levels of sex hormones, including bio-available testosterone, in patients with acute myocardial infarction and in control subjects. In addition, changes in hormone levels in patients were compared with alterations in the fibrinolytic profile. Thirty male patients admitted with chest pain were studied. Twenty two had acute myocardial infarction and eight had non-specific chest pain. Plasma levels of total and bio-available testosterone, 17β-estradiol, sex hormone binding globulin and insulin were measured at baseline and throughout admission. In addition, fibrinolytic factors (plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (tPA) and fibrinogen) were measured in patients who received fibrinolysis. Height and weight, and the subsequent development of heart failure or myocardial dysfunction were also recorded. Patients had lower levels of bio-available testosterone (2.07±0.75 nmol/L vs. 5.3±1.7 nmol/L, p<0.05) and higher levels of 17β-estradiol (87.9±39.5 pmol/L vs. 48.1±18.4 pmol/L, p<0.001) than controls. Total and bio-available testosterone levels fell acutely following myocardial infarction (11.9±3.8 nmol/L to 9.7±3.3 nmol/L, p<0.05; 1.95±0.76 nmol/L to 1.55±0.67 nmol/L, p<0.05). This reduction was associated with elevation of PAI-1 activity and reduction of tPA activity, independent of changes in plasma insulin levels. Patients with lower baseline levels of testosterone and higher levels of 17β-estradiol had a relatively pro-thrombotic fibrinolytic profile and increased risk of complications. In conclusion, total and bio-available levels of testosterone fall following acute myocardial infarction in men, in association with adverse changes in fibrinolytic profile. It is not clear whether this association represents a direct effect of testosterone on thrombotic tendency but warrants further investigation.