Testosterone: a natural tonic for the failing heart?
P.J. Pugh, K.M. English, T.H. Jones1 and K.S. Channer
http://qjmed.oupjournals.org/cgi/content/full/93/10/689
Department of Cardiology,
Royal Hallamshire Hospital
Department of Human Metabolism and Clinical Biochemistry,
University of Sheffield, Sheffield, UK
... A study of 53 men with CHF [Chronic congestive heart failure] found that dehydroepiandrosterone (DHEA) levels were significantly lower than in healthy controls. In 17 men with non-ischaemic cardiomyopathy, testosterone levels correlated with cardiac index, and five men with severe left ventricular dysfunction had markedly reduced plasma testosterone, which normalized 2 months after implantation of a ventricular assist device. In an animal model of heart failure, hamsters with cardiomyopathy were found to have very low testosterone levels.
... to be expected given the effect of chronic disease on gonadal function. However, there is also a link between hypotestosteronaemia and stable CAD. Epidemiological data suggest that men with ischaemic heart disease have low androgen levels, and men with proven coronary atheroma have lower testosterone levels than healthy controls. In [laboratory] animals, castration promotes atherosclerosis while androgen therapy retards it. Similarly, hypertensive men have relatively low androgen levels, which show an inverse correlation with blood pressure.11 Men with CHF, therefore, are likely to have low testosterone levels, potentially exacerbating the catabolic imbalance.
There are no clinical trial data concerning the effects of testosterone on left ventricular function. In rats, androgen therapy improves coronary blood flow and increases both fractional shortening and peak myocardial oxygen consumption, thereby improving cardiac function.14 Castration results in reduced ejection fraction and diastolic dysfunction, with alteration of the isoenzyme composition of the myosin heavy chain.
Testosterone therapy has been used to treat men with angina; the beneficial effects on both ischaemia and exercise tolerance have been demonstrated in several studies.
In humans, testosterone reduces blood pressure and enhances relaxation of brachial arteries; direct injection into coronary arteries produces dilatation and increased coronary blood flow. Low circulating levels of testosterone may therefore contribute to the generalized increase in vascular tone found in patients with CHF. A vasodilator effect could be important in relieving pulmonary congestion and improving peripheral perfusion. Androgen therapy could therefore also improve cardiac function by reducing pre-load and after-load and by increasing coronary blood flow.
Fatigue and poor exercise tolerance are central features of the symptoms of heart failure, and may be out of proportion to the degree of left ventricular dysfunction. Patients with CHF suffer loss of skeletal muscle mass with reduced muscle strength and endurance. Muscle fibre type and mitochondrial structure are altered, with reduction in the enzymes of the Krebs cycle and oxidative chain. ...
Testosterone deficiency is likely to contribute to the weakness and fatigue of CHF which constitute a major aspect of the morbidity. Androgen therapy could potentially improve patient well-being by combating this. ... Testosterone has been found to increase IGF-1 levels and reduce hyperinsulinaemia and insulin resistance.
It is now recognized that cytokine activation is likely to play an important role in the progression of cardiac failure. ... Circulating levels of tumour necrosis factor (TNF) and interleukin-6 (Il-6) are elevated in CHF and independently predict mortality. The levels correlate adversely with several prognostic markers, including NYHA class, exercise tolerance and myocardial oxygen consumption, as well as plasma levels of ANP, catecholamines, endothelin-1 and angiotensin.
TNF is produced mainly by macrophages [especially in systemic disease], but also by the myocardium in CHF. It impairs synthesis and promotes catabolism of skeletal muscle, and reduces testosterone production. It causes endothelial dysfunction and impairs production of NO by endothelium.55 Administration causes left ventricular dysfunction and heart failure in humans; anti-TNF therapy may improve cardiac function.56,57 Cytokines therefore appear to mediate many of the pathophysiological processes of heart failure.
The immune-modulatory properties of androgens have been well described. In various disease models (though not in heart failure), androgens have been found to significantly suppress macrophage production of cytokines both in vitro and in vivo. In man, androgen levels correlate negatively with plasma cytokine levels and gonadotropin therapy suppresses the high level seen in hypogonadal men.
Patients with chronic heart failure suffer considerable morbidity as well as early mortality. They exhibit altered structure and function of cardiac and skeletal muscle and excessive activation of catabolic hormones and inflammatory cytokines. Men with CHF have relatively low androgen levels, which may contribute to the pathophysiological process. Androgen replacement therapy could potentially ameliorate symptoms by improving cardiac and vascular function and increasing strength and endurance. It may also redress the catabolic/anabolic imbalance of chronic CHF and suppress the cytokine activation which leads to progression of the disease. ....