Testosterone is an important regulator of cardiovascular function that exerts its influence through multiple pathways. It produces changes in cardiomyocytes, which lead to pathological remodeling and eventually heart failure due not only to testosterone’s effects on contractility or energy metabolism but also because it influences inflammation by promoting fibrosis during myocarditis situations where viruses are localised at the site(1).
Testosterone is a hormone that possesses both cardioprotective and harmful effects. In some cases, low levels of testosterone have been linked with heart disease while in other circumstances it seems to protect against these conditions. This review will explore the ways in which this interacts between our hormones and how they affect us as individuals or populations.
What is testosterone?
Testosterone (T) is the principal male sex hormone and is secreted primarily by the testes. Only 1%–2% of testosterone circulates in the blood as free testosterone, and the remaining is bound to proteins including albumin and sex steroid hormone-binding globulin (SHBG).
What are the effects of testosterone?
Plasma levels of T vary with circadian rhythm and fluctuate throughout life. Aging is associated with a gradual decline in testosterone levels in men and an increase in circulating SHBG levels. In addition to its anabolic and androgenic effects, testosterone has important effects on the cardiovascular system. The cardiac effects of testosterone are influenced by plasma levels, cellular metabolism, modulation of intracellular pathways, and androgen receptor expression.
What does testosterone do for the heart?
Testosterone influences the cardiovascular system by acting directly on cardiac cells. Cardiomyocytes express receptors for all major sex steroid hormones including testosterone and are thus exposed to their modulatory effects on myocardial cell physiology. Testosterone has an important role in intracellular Ca2+homeostasis. Mediated by the androgen receptor, testosterone activates L-type calcium channels, which increase the intracellular levels of calcium and thus regulate myocardial contractility.
Testing on animals
Gonadectomy in adult male rats reduces the contractility of isolated cardiac myocytes, and short-term androgen exposure stimulates the contractility of isolated rat ventricular myocytes. Additionally, in castrated animals, androgen therapy improves coronary blood flow and increases both fractional shortening and peak myocardial oxygen consumption, thereby improving cardiac function.
How important is testosterone for the human body?
Testosterone has been shown to elicit cardioprotective effects, and several intracellular mechanisms have been identified. Through genomic and nongenomic mechanisms, testosterone influences apoptosis, regulates leukocyte migration and reactive oxygen species (ROS) generation, and the nitric oxide (NO) – guanosine 3′,5′-cyclic monophosphate (cGMP) pathway.
There is a strong association between low testosterone and chronic heart failure. This may be one reason why men with the condition have an increased risk for death, according to some studies.