Testosterone has beneficial
effects on several cardiovascular risk factors, which include cholesterol, endothelial dysfunction and inflammation
In clinical studies, acute and chronic testosterone administration increases coronary artery diameter and flow, improves
cardiac ischaemia and symptoms in men with chronic stable angina and reduces peripheral vascular resistance in chronic heart
failure.
testosterone is an L-calcium channel blocker and induces potassium
channel activation in vascular smooth muscle cells
Animal studies have consistently demonstrated that testosterone is atheroprotective,
whereas testosterone deficiency promotes the early stages of atherogenesis
there is no compelling evidence that testosterone replacement to levels within the normal healthy range contributes
adversely to the pathogenesis of CVD (Carson & Rosano 2011) or prostate cancer (Morgentaler & Schulman 2009)
bidirectional effect between decreased testosterone
concentrations and disease pathology exists as concomitant cardiovascular risk factors (including inflammation, obesity and
insulin resistance) are known to reduce testosterone levels and that testosterone confers beneficial effects on these cardiovascular
risk factors
Achieving a normal physiological testosterone concentration through the administration
of testosterone replacement therapy (TRT) has been shown to improve risk factors for atherosclerosis including reducing central
adiposity and insulin resistance and improving lipid profiles (in particular, lowering cholesterol), clotting and inflammatory
profiles and vascular function
It is well known that impaired erectile function and CVD are closely
related in that ED can be the first clinical manifestation of atherosclerosis often preceding a cardiovascular event by 3–5
years
no decrease in the response (i.e. no tachyphylaxis) of testosterone and that patient benefit persists in the long term.
free testosterone
levels within the physiological range, has been shown to result in a marked increase in both flow- and nitroglycerin-mediated
brachial artery vasodilation in men with CAD
Clinical studies, however, have revealed either small reductions of 2–3 mm in diastolic pressure or no significant effects
when testosterone is replaced within normal physiological limits in humans
Endothelium-independent mechanisms of testosterone
are considered to occur primarily via the inhibition of voltage-operated Ca2+ channels (VOCCs) and/or activation of K+ channels (KCs) on smooth muscle cells (SMCs)
Testosterone shares the same molecular binding site as nifedipine
Testosterone increases the expression of endothelial nitric oxide synthase (eNOS)
and enhances nitric oxide (NO) production
Testosterone also inhibited
the Ca2+ influx response to PGF2α
one of the major actions of testosterone is on NO and its signalling pathways
In addition to direct effects on NOS expression, testosterone may also affect phosphodiesterase type 5 (PDE5 (PDE5A)) gene expression, an enzyme controlling the degradation of cGMP, which acts as a vasodilatory second messenger
the significance of the action of testosterone on VSMC apoptosis and proliferation in atherosclerosis is difficult
to delineate and may be dependent upon the stage of plaque development
Several human studies have shown that carotid IMT (CIMT) and aortic calcification negatively correlate
with serum testosterone
t long-term testosterone treatment reduced CIMT in men with low testosterone levels
and angina
neither intracellular nor membrane-associated
ARs are required for the rapid vasodilator effect
acute responses appear to be AR independent, long-term AR-mediated effects on the vasculature have also been described,
primarily in the context of vascular tone regulation via the modulation of gene transcription
Testosterone and DHT increased the expression of eNOS in HUVECs
oestrogens have been shown to activate eNOS and stimulate NO production in an ERα-dependent manner
Several studies, however, have demonstrated that the vasodilatory actions of testosterone are not reduced by aromatase
inhibition
non-aromatisable DHT elicited similar vasodilation to testosterone treatment in arterial smooth muscle
increased endothelial NOS (eNOS) expression and phosphorylation were observed in testosterone- and DHT-treated
human umbilical vein endothelial cells
Androgen deprivation leads to a reduction in neuronal NOS expression associated with a decrease of intracavernosal pressure
in penile arteries during erection, an effect that is promptly reversed by androgen replacement therapy
Observational evidence suggests that several pro-inflammatory cytokines (including interleukin 1β (IL1β), IL6, tumour necrosis
factor α (TNFα), and highly sensitive CRP) and serum testosterone levels are inversely associated in patients with CAD, T2DM
and/or hypogonadism
patients with the
highest IL1β concentrations had lower endogenous testosterone levels
TRT has been reported to significantly
reduce TNFα and elevate the circulating anti-inflammatory IL10 in hypogonadal men with CVD
testosterone treatment to normalise levels in hypogonadal men with the MetS
resulted in a significant reduction in the circulating CRP, IL1β and TNFα, with a trend towards lower IL6 compared with placebo
parenteral testosterone undecanoate, CRP decreased significantly in hypogonadal elderly
men
Higher levels of serum adiponectin have been shown to lower cardiovascular risk
Research suggests that the expression of VCAM-1, as induced by pro-inflammatory cytokines such as TNFα or interferon γ (IFNγ
(IFNG)) in endothelial cells, can be attenuated by treatment with testosterone
Testosterone also inhibits the production of pro-inflammatory cytokines such as IL6, IL1β and TNFα in a range of cell types
including human endothelial cells
decreased inflammatory response to TNFα and lipopolysaccharide (LPS) in
human endothelial cells when treated with DHT
The key to unravelling the link between testosterone
and its role in atherosclerosis may lay in the understanding of testosterone signalling and the cross-talk between receptors
and intracellular events that result in pro- and/or anti-inflammatory actions in athero-sensitive cells.
testosterone
functions through the AR to modulate adhesion molecule expression
pre-treatment with DHT reduced the cytokine-stimulated inflammatory response
DHT inhibited NFκB activation
DHT could inhibit an LPS-induced upregulation of MCP1
Both NFκB and
AR act at the transcriptional level and have been experimentally found to be antagonistic to each other
As the AR and NFκB are mutual antagonists, their interaction and influence on functions can be bidirectional, with inflammatory
agents that activate NFκB interfering with normal androgen signalling as well as the AR interrupting NFκB inflammatory transcription
prolonged exposure of vascular cells to the inflammatory activation of NFκB associated with atherosclerosis
may reduce or alter any potentially protective effects of testosterone
DHT and IFNγ also modulate each other's signalling through interaction at the transcriptional
level, suggesting that androgens down-regulate IFN-induced genes
(Simoncini et al. 2000a,b). Norata et al. (2010) suggest that part of the testosterone-mediated atheroprotective effects could depend on ER activation mediated by the testosterone/DHT
3β-derivative, 3β-Adiol
TNFα-induced induction of ICAM-1, VCAM-1 and E-selectin as well as MCP1 and IL6 was significantly
reduced by a pre-incubation with 3β-Adiol in HUVECs
3β-Adiol also reduced LPS-induced gene expression
of IL6, TNFα, cyclooxygenase 2 (COX2 (PTGS2)), CD40, CX3CR1, plasminogen activator inhibitor-1, MMP9, resistin, pentraxin-3 and MCP1 in the monocytic cell line U937 (Norata et al. 2010)
This study suggests that testosterone metabolites, other than those generated through aromatisation, could exert anti-inflammatory
effects that are mediated by ER activation.
The authors suggest that DHT differentially
effects COX2 levels under physiological and pathophysiological conditions in human coronary artery smooth muscle cells and
via AR-dependent and -independent mechanisms influenced by the physiological state of the cell
There are, however, a number of systematic meta-analyses of clinical trials of TRT that have not demonstrated
an increased risk of adverse cardiovascular events or mortality
The TOM trial, which was designed to investigate the effect of TRT on frailty in elderly men, was terminated prematurely
as a result of an increased incidence of cardiovascular-related events after 6 months in the treatment arm
trials of TRT in men with either chronic stable angina or chronic cardiac failure have also found no increase
in either cardiovascular events or mortality in studies up to 12 months
Evidence may therefore suggest that low testosterone levels and testosterone levels above the normal range have an adverse
effect on CVD, whereas testosterone levels titrated to within the mid- to upper-normal range have at least a neutral effect
or, taking into account the knowledge of the beneficial effects of testosterone on a series of cardiovascular risk factors,
there may possibly be a cardioprotective action
The effect of testosterone on human vascular function is a complex issue and may be dependent upon the underlying androgen
and/or disease status.
the majority of studies suggest that testosterone may display both acute and
chronic vasodilatory effects upon various vascular beds at both physiological and supraphysiological concentrations and via
endothelium-dependent and -independent mechanisms
The androgens testosterone and DHT elicit vasodilation via calcium and potassium channel activation. The vasodilatory effect of the androgens is through, in part, due to K activated Ca channels. Also of note, DHT had the same effect and DHT cannot be aromatized to estrogen.
Physiologic levels of testosterone shown to induce Calcium channel blockade. This induces the beneficial cardiovascular vasodilation. It is known that testosterone binds to the same receptor as the common calcium channel blocker nifedipine.
In this animal study, testosterone induces vasodilation via a non-classical genomic pathway. Likely independent of androgen receptor. Also, aromatase inhibition does not diminish the vasodilatory effect of testosterone.
NS contains 154 mM Na+ and Cl-, with an average pH of 5.0 and osmolarity of 308 mOsm/L.
LR solution has an average pH of 6.5, is hypo-osmolar (272 mOsm/L), and has similar electrolytes (130 mM Na+, 109 mM Cl-, 28 mM lactate, etc.) to plasma
LR’s acid base balance is superior to that of NS’s
There were no significant differences between LR and NS groups in fibrinogen concentrations or platelet count
Total protein dropped
no significant differences in Hct (Table
1) or total protein between LR and NS groups
Bicarbonate HCO3- levels were decreased by hemorrhage but returned to pre-hemorrhage values by 3 h after LR resuscitation, whereas no return was observed with NS resuscitation
Na+ was increased after NS resuscitation
No changes in Na+ or K+ were observed
K+ did not change initially after NS resuscitation but was elevated at 6 h afterwards
Ca++ was similarly decreased
Cl- was elevated for 6 h after NS resuscitation, with no changes shown after LR resuscitation
PT was similarly prolonged by resuscitation with LR (from 11.2 ± 0.2 sec at baseline to 12.1 ± 0.2 sec at 6 h) and NS
Plasma aPTT was also similarly prolonged by resuscitation with LR (from 17.1 ± 0.5 sec baseline to 20.1 ± 1.2 sec at 6 h) or NS
NS resuscitation resulted in better oxygen delivery and oxygen delivery-to-oxygen demand ratio as an index of oxygen debt
NS had better tissue perfusion and oxygen metabolism than LR
LR resuscitation returned BE and bicarbonate to pre-hemorrhage levels within 3 h, but no return of BE or bicarbonate was observed for 6 hr with NS resuscitation
current blood bank guidelines state that LR should not be mixed with blood to prevent the risk of clot formation from calcium included in LR
LR resuscitation should not be given with blood through the same iv-line and crystalloids should be avoided in patients with blood transfusion
PT and aPTT were prolonged for 6 h after hemorrhage and resuscitation, suggesting a hypocoagulable states
potential thrombotic risk from LR resuscitation is unlikely.
we suspected that the blood pressure after NS resuscitation would be lower than that of LR due to its vasodilator effects
NS required a larger resuscitation volume and was associated with poor acid base status and elevated serum potassium in this model
NS required 50% more volume and was associated with a higher cardiac output and lower peripheral resistance, as compared to LR resuscitation
These differences are possibly due to the vasodilator effects from NS
an elevation of K+ was observed at 6 h post NS resuscitation, while no change of K+ was observed after LR resuscitation
The mechanism for the increase of K+ from NS is not fully known
NS is associated with vasodilator effects and the risks of metabolic acidosis and hyperkalemia
IV Vitamin C improves endothelial vasodilation in essential hypertension. The Vitamin C reduces the oxygen free radicals which allowed eNOS to increase NO production. Two take homes: oxygen free radicals may be responsible for the endothelial dysfunction that leads to essential hypertension and vitamin C, particularly IV, can be used to counter this process. Other studies have shown IV vitamin C to be anti-hypertensive in its action.
testosterone therapy has tremendous cardiovascular benefit in men with low T. The key here is physiologic replacement of Testosterone. Testosterone is a vasodilator and anti-inflammatory agent in men with low T. Testosterone therapy improves cardiac function in those with DHF and angina. Testosterone is found to be a Ca++ channel blocker--anyone say hypertension treatment?
Some startling statistics in this 2013 review on Testosterone in men. Studies reflect an inverse relationship between Testosterone and CAD severity. That is, the lower the Testosterone levels, the increase in severity of CAD. This same association was also found with CHF. Low Testosterone is common in those with CAD, CHF, type II diabetes, increased IMT in carotids and aorta, and obesity when compared to "healthy" individuals. Testosterone therapy in those with CAD found benefits: prolongation of ST segment depression, coronary vasodilation, improved exercise capacity in those with CHF, shift to type I muscle fibers, shorten the QTc interval. Testosterone therapy has been shown to improve insulin resistance, improve HgbA1c and decrease waist circumference and fat loss in obese individuals. Otherwise, a good review of the association between a declining Testosterone and cardiovascular disease.
the reduction in BP within the first 10–20 min may be primarily attributed to a direct vasodilatory physiological effect, described as venodilation
BP reduction observed after 70–90 min is likely attributable to pharmacokinetically plausible vitamin C absorption and vasodilation because of nitric oxide release
Pharmacokinetic studies of IVC administration observed peak plasma levels within the first 90 min, with plasma levels reaching 13350 μmol/l for 50 g of IVC
Essential hypertension, associated with endothelial dysfunction because of an impaired nitric oxide/l-arginine pathway and impaired vasodilation can be restored by vitamin C
marked increase in BP response when IVB12 is administered
The mean BP increased significantly up to 12–16 mmHg systolic and diastolic independent of the dosage of vitamin B12
The production of norepinephrine, which can stimulate angiotensin-II production, which in turn influences BP, has been suggested as a possible mechanism for the increase in BP with IVB12
excess norephinephrine levels stimulate the sympathetic nervous system, leading to increased cortisol production, which has also been linked to increases in BP
Animal studies have found higher serum levels of norepinephrine (noradrenaline) in the adrenal medulla of rats receiving methylcobalamin (methyl-vitamin B12)
IV vitamin C in mostly normotensive patients (> 30 grams) reduced blood pressure. Some of the patients were pre-hypertensive. Vitamin B12 increase the blood pressure.
another animal study, but blockade of androgen receptor, in this study, was not found to diminish the vasodilatory effect of testosterone. This indicates that some of the vasoactive responses to testosterone are independent of AR and this has been shown in other studies ie. AR knockout mice.
The vast majority (88%) did not screen cardiac patients for TDS.
Testosterone deficiency has a prevalence of 7% in the general population, rising to 20% in elderly males
Males with CAD have lower testosterone levels than those with normal coronary angiograms of the same age,5 suggesting that the prevalence of testosterone deficiency is much higher in the CAD population
Men with hypertension, another established risk factor for CAD, have lower testosterone compared to normotensive men
Recent meta-analyses showed that testosterone levels are generally lower among patients with metabolic syndrome, regardless of the various definitions of metabolic syndrome that are used
Testosterone (total and bioavailable) and sex-hormone binding globulin (SHBG) are inversely associated with the prevalence of metabolic syndrome in men between the ages of 40 and 80, and this association persists across racial and ethnic backgrounds
ower levels of testosterone and SHBG predict a higher incidence of metabolic syndrome.
Low testosterone levels have been related to increased insulin resistance and cardiovascular mortality,12 even in the absence of overt type 2 diabetes mellitus.
testosterone levels (total and bioavailable) in middle-aged men are inversely correlated with insulin resistance
The Massachusetts Male Aging Study (MMAS) demonstrated that low levels of testosterone and SHBG are independent risk factors for the development of type 2 diabetes,
Andropausal men (age 58 ± 7 years) have a higher maximal carotid artery intima-media thickness
There is an inverse linear correlation between body mass index (BMI) and wait-to-hip ratio with testosterone and insulin-like growth factor-1 levels.
Testosterone supplementation for 1 year in hypogonadal men has been shown to cause a significant improvement in body weight, BMI, waist size, lipid profile, and C-reactive protein levels
TRT for 3 months in hypogonadal men with type 2 diabetes significantly improved fasting insulin sensitivity, fasting blood glucose and glycated hemoglobin.
Testosterone replacement can improve angina symptoms and delay the onset of cardiac ischemia, likely through a coronary vasodilator mechanism
ADT is associated with an increased risk of cardiovascular events, including myocardial infarction and cardiovascular mortality.
ADT significantly increases fat mass, decreases lean body mass,29,30 increases fasting plasma insulin and decreases insulin sensitivity31 and increases serum cholesterol and triglyceride levels
Startling study on the knowledge of Testosterone and cardiovascular disease in general practitioners and cardiologists in Canada. Eight-eight percent did not screen patients with cardiovascular disease for low Testosterone. A whopping 67% of physicians did not know that low T was a risk factor for cardiovascular disease, yet 62% believed Testosterone would increase exercise tolerance.
The lack of knowledge displayed by physicians today is staggering and is an indictment of the governing bodies. This was a survey conducted in Canada so there are obvious limitations to the strength/conclusion of this study.