Testosterone Replacement Therapy: Effects on Blood Pressure in Hypogonadal Men

PURPOSE

While testosterone therapy can improve the various pathologies associated with adult-onset testosterone deficiency (TD), Summary of Product Characteristics (SPC) of five testosterone preparations caution that treatment may be associated with hypertension. This paper evaluates the impact of testosterone undecanoate (TU) on blood pressure (BP) in men with adult-onset TD.

MATERIALS AND METHODS

Of 737 men with adult-onset TD in an on-going, observational, prospective, cumulative registry, we studied changes in BP using non-parametric sign-rank tests at final assessment and fixed time points. We used multiple regression analysis to establish factors (baseline BP, age, change/baseline waist circumference [WC] and hematocrit [HCT] and follow-up) potentially associated with BP change in men on TU.

RESULTS

TU was associated with significant reductions in systolic, diastolic BP and pulse pressure, regardless of antihypertensive therapy (at baseline or during follow-up), larger reductions were seen with concurrent antihypertensive therapy. In men never on antihypertensive agents, median changes (interquartile range [IQR]) in systolic BP, diastolic BP and pulse pressure were -12.5 (-19.0, -8.0), -8.0 (-14.0, -3.0), and -6.0 (-10.0, -1.0) mmHg, respectively at final assessment, with only baseline BP values inversely associated with these changes (HCT and WC were not significantly associated). In men not on TU, systolic BP, diastolic BP, and pulse pressure significantly increased. In the TU treated men only 1 of the 152 men (not on antihypertensive agents at baseline) were started on antihypertensives during follow-up. In contrast 33 of the 202 men on antihypertensives (at baseline or follow-up) had the antihypertensive agent discontinued by the end of the follow-up.

CONCLUSIONS

TU was associated with lowering of BP during follow-up irrespective of antihypertensive therapy, with greater reductions in men with higher baseline BP. In the context of SPC warnings, our long-term data provide reassurance on the effect of TU on BP.

Testosterone replacement therapy: association with mortality in high-risk patient subgroups

OBJECTIVES

We describe studies determining the association between testosterone therapy (TTh) and mortality.

MATERIALS & METHODS

We used a registry database of 737 men with adult-onset testosterone deficiency defined as presenting with low serum total testosterone (TT) levels ≤12.1 nmol/L and associated symptoms over a near 10-year follow-up. We compared associations between testosterone undecanoate (TU), cardio-metabolic risk factors and mortality using non-parametric statistics followed by separate Cox regression models to determine if any association between TU and morality was independent of age and cardio-metabolic risk factors. Finally, the association between TU and mortality was studied in men stratified by cardio-metabolic risk.

RESULTS

During a median follow-up interquartile range (IQR) of 114 (84-132) months, 94 of the 737 men died. TU (ref: non-treatment) was associated with mortality; hazard ratio = 0.23, 95% confidence intervals = 0.14-0.40. Cox's regression models showed the above association to be independent of baseline age, waist circumference, hemoglobin A1c, lipids, blood pressure, smoking, and type 2 diabetes. These variables remained associated with mortality. We finally stratified the men by the high-risk baseline variables and established that the association between mortality and TU was only evident in men at higher risk. A possible explanation could lie with the "law of initial value," where greater improvements are evident following treatment in patients with worse baseline values.

CONCLUSIONS

This study with long follow-up confirms that TTh is associated with lower mortality in men with adult-onset TD. This association was evident only in men with greater cardio-metabolic risk factors who demonstrated greater benefit.

Age and the Residual Risk of Cardiovascular Disease following Low Density Lipoprotein-Cholesterol Exposure

We believe that there is sufficient evidence from basic science, longitudinal cohort studies and randomised controlled trials which validates the low-density lipoprotein cholesterol (LDL-C) or lipid hypothesis. It is important that we can communicate details of the cardiovascular disease (CVD) risk reduction that the average patient could expect depending on the scale of LDL-C decrease following lipid lowering therapy. It is also essential that residual risk (ResR) of CVD be highlighted. To achieve this aim by using existing trial evidence, we developed mathematical models initially for relative risk reduction (RRR) and absolute risk (AR) reduction and then showed that despite optimising LDL-C levels, a considerable degree of ResR remains that is dependent on AR. Age is significantly associated with AR (odds ratio: 1.02, 95% confidence intervals: 1.01-1.04) as was previously demonstrated by analysing the Whickham study cohort using a logistic regression model (age remaining significant even when all the other significant risk factors such as sex, smoking, systolic blood pressure, diabetes and family history were included in the regression model). A discussion of a paper by Ference et al. provided detailed evidence of the relationship between age and AR, based on lifetime LDL-C exposure. Finally, we discussed non-traditional CVD risk factors that may contribute to ResR based on randomised controlled trials investigating drugs improving inflammation, thrombosis, metabolic and endothelial status.

The association of peak systolic velocity in the carotid artery with coronary heart disease: A study based on portable ultrasound

Cardiovascular disease (CVD) is the highest cause of death globally with more people dying annually from it than from any other cause. CVD is associated with modifiable risk factors (dyslipidaemia, hypertension and diabetes) and treating each of these factors lowers the risk of CVD. It is impossible to estimate the benefit of risk factor modification in the individual patient and extrapolating data from multiple trials is difficult. It would be useful to have a marker of risk that accurately estimates real time risk by measuring blood flow factors associated with the pathogenesis of atheroma. The aim of this preliminary study was to validate a low-cost measurement technique for obtaining blood flow velocity profiles and assess whether any of the measured and calculated factors, based on computational fluid dynamics (CFD) simulation, known to be associated with atheroma was associated with coronary heart disease (CHD), thus establishing its feasibility and acceptability as a clinical tool and suggesting areas for future research. Our study identified (i) that mean peak systolic (PS) velocity being associated with CHD; individuals without CHD: mean (SD) = 62.8 (16.1) cm/s, with CHD: mean (SD)  = 53.6 (17.3) cm/s, p = 0.042; and (ii) that low-cost, portable ultrasound, which is routinely available in general practice, is a suitable assessment tool.

Testosterone Therapy: An Assessment of the Clinical Consequences of Changes in Hematocrit and Blood Flow Characteristics

INTRODUCTION

Clinical guidelines indicate that hematocrit should be monitored during testosterone replacement therapy (TTh), with action taken if a level of 0.54 is exceeded.

AIM

To consider the extent of changes in hematocrit and putative effects on viscosity, blood flow, and mortality rates after TTh.

METHODS

We focused on literature describing benefits and possible pitfalls of TTh, including increased hematocrit. We used data from the BLAST RCT to determine change in hematocrit after 30 weeks of TTh and describe a clinical case showing the need for monitoring. We consider the validity of the current hematocrit cutoff value at which TTh may be modified. Ways in which hematocrit alters blood flow in the micro- and macro-vasculature are also considered.

MAIN OUTCOME MEASURES

The following measures were assessed: (i) change in hematocrit, (ii) corresponding actions taken in clinical practice, and (iii) possible blood flow changes following change in hematocrit.

RESULTS

Analysis of data from the BLAST RCT showed a significant increase in mean hematocrit of 0.01, the increase greater in men with lower baseline values. Although 0 of 61 men given TTh breached the suggested cutoff of 0.54 after 30 weeks, a clinical case demonstrates the need to monitor hematocrit. An association between hematocrit and morbidity and mortality appears likely but not proven and may be evident only in patient subgroups. The consequences of an increased hematocrit may be mediated by alterations in blood viscosity, oxygen delivery, and flow. Their relative impact may vary in different vascular beds.

CONCLUSIONS

TTh can effect an increased hematocrit via poorly understood mechanisms and may have harmful effects on blood flow that differ in patient subgroups. At present, there appears no scientific basis for using a hematocrit of 0.54 to modify TTh; other values may be more appropriate in particular patient groups. König CS, Balabani S, Hackett GI, et al. Testosterone Therapy: An Assessment of the Clinical Consequences of Changes in Hematocrit and Blood Flow Characteristics. Sex Med Rev 2019;7:650-660.

Association between triglyceride and high-density lipoprotein cholesterol change following fibrate therapy

BACKGROUND

Debate surrounding the role of fibrates has followed mixed outcomes from several randomised controlled trials. Subgroup analysis of even the negative trials reveals significant reduction in cardiovascular risk amongst patients with low HDL-C and high TG. We previously described factors associated with HDL-C change following fibrates. As fibrates influence both HDL-C and TG levels via their action on PPAR-α, we now wished to study TG change following fibrate therapy and any associations with baseline and change in HDL-C and TC levels.

METHODS

Data was collected from case notes of patients started on fibrates (n=248) between 2002 and 2008 in the lipid clinics at Heart of England NHS Foundation Trust. Regression analyses were carried out to determine factors associated with changes in TG.

RESULTS

Multiple regression analysis revealed that TG change was associated with pre-treatment TG (p<0.001) and TC levels (p=0.029). The association between TG change and pre-treatment TG remained significant when all factors including gender, concurrent statin treatment, diabetes and baseline HDL-C were entered into the regression model. Our previous study demonstrated significant post-fibrate HDL-C change in the group with baseline HDL-C values <1.0mmol/l. In our present study significant TG reduction was observed regardless of the baseline patient characteristics including HDL-C levels.

CONCLUSIONS

The actions of fibrates are considered to be mediated via PPAR-α, but our data suggest that the effects on TG and HDL-C are different. Thus, the mechanisms mediating the changes of these lipids following fibrate treatment may vary.

Numerical model for the investigation of dual-flow in a spiral counter-current chromatography column

In dual-flow counter-current chromatography (DF-CCC), the two immiscible liquids are flowing in opposite directions in the coil. The method allows for the continuous separation of two solutes. In this study a numerical model was developed to allow for the detailed investigation of flow in such columns. The mesh model of the presented DF spiral column was developed in line with an existing experimental model. The paper presents results during the early filling stages for different rotation directions. These clearly illustrate the performance of the developed model by (1) confirming the importance of flowing the lighter phase from tail to head and the heavier phase from head to tail and (2) by visualising mixing waves and the recognised back and forth "swish-swash" motion as present in CCC in that operating mode.

Flow mixing and fluid residence times in a model of a ventricular assist device

To provide a reliable tool for predicting the flow in a clinical sac-type ventricular assist device (VAD), a simplified model VAD was developed prior to this study for the purpose of experimental validation of computer simulations of the time-varying flow on a moving grid. At selected locations in the flow field, flow patterns, vortex core trajectories and velocities were compared between the numerical and physical models during one full pumping cycle. The computer simulations showed qualitatively very good agreement with the experiment. Quantitatively, the agreement was less favourable. In order to investigate flow mixing and to evaluate fluid residence times in the model VAD a new tool has been developed: the numerical simulations were extended by injecting a scalar into the flow domain. These simulations allow investigation of the flow mixing qualitatively by visualisation and quantification of fluid residence times. Experimental assessment of the numerical results using dye injection proved to be favourable. The numerical results have been extended to include some prediction of pressure which have been compared with experimental measurements.

Comparison of flow in numerical and physical models of a ventricular assist device using low- and high-viscosity fluids

The flows in a model of a ventricular assist device (VAD) were investigated numerically and experimentally for two different Newtonian test fluids. These were a blood analogue fluid and a much higher viscosity fluid. A finite volume method was employed to solve the governing equations for a three-dimensional unsteady laminar flow on a transient grid. The numerical solutions were compared with experimental results from an identical physical model. The experimental flows were investigated by flow visualization and by laser Doppler velocity measurements at selected points in the flow field. The validation was based on comparisons of flow patterns and of non-component velocity-time histories. The maximum Reynolds numbers in the inflow tube of the model VAD were approximately 460 and 3300 using the high- and low-viscosity fluids respectively. The investigation showed that the flow patterns were better predicted for the high-viscosity fluid. However, the agreement between the velocity-time histories was found to be slightly better for the low-viscosity fluid. The discrepancies in the flow patterns may be due to intermittent turbulence with a further contribution from numerical diffusion.

Investigation of unsteady flow in a model of a ventricular assist device by numerical modelling and comparison with experiment

Prior to this study, a clinical prototype of a sac-type ventricular assist device (VAD) was investigated experimentally, using both flow visualisation and Laser Doppler anemometry (LDA), in order to optimise its geometry. As poor optical access precluded the experimental investigation of the flow in some areas of the prototype VAD, computational fluid dynamics (CFD) was used in the present work. Flow patterns during one full pumping cycle were investigated in a simplified model of the VAD. The numerical solutions were compared with experimental results from an identical physical model. The model consists of the hemispherical cylinder and two attached tubes for the inflow and outflow. Instead of a diaphragm in the clinical device, which deforms non-uniformly during pumping, a piston with a matching hemispherical crown was used. A finite volume method was employed to solve the governing equations for the three-dimensional, unsteady, laminar flow of an incompressible, Newtonian fluid. The general flow features were predicted very well by the simulation, with some differences in the details of the flow structures. This allows the conclusion that CFD can be used to facilitate improvement of the design of the clinical device. The comparison of one-component velocity time histories at selected points showed that the predicted velocities were approximately 20-50% lower than those measured by LDA. Such underprediction would lead to erroneous results for particle residence times and may result in an underestimation of wall shear stresses.