Influence of Baseline Serum Testosterone on Changes in Body Composition in Response to Testosterone Therapy

Testosterone replacement alters the cell size in visceral fat but not in subcutaneous fat in hypogonadal aged male rats as a late-onset hypogonadism animal model

Background

Patients with late-onset hypogonadism (LOH) benefit from testosterone replacement by improvement in the parameters of the metabolic syndrome, but fat cell morphology in these patients is still unclear. This study aims to determine the effect of testosterone replacement on the morphology of fat cells in subcutaneous and visceral adipose tissue and on erectile function in hypogonadal aged male rats as a model of LOH.

Methods

Ten male Sprague-Dawley rats aged 20–22 months were randomly allocated to two groups, ie, aged male controls (control group, n=5) and aged males treated with testosterone replacement therapy (TRT group, n=5). Testosterone enanthate 25 mg was injected subcutaneously every 2 weeks for 6 weeks. At 6 weeks, the intracavernous pressure (ICP) and mean arterial blood pressure (MAP) ratio was assessed. Visceral and subcutaneous adipose tissue specimens were collected and analyzed using Image-J software.

Results

Body weight at 2, 4, and 6 weeks after TRT was 800.0±35.4 g, 767.5±46.3 g, and 780±40.4 g, respectively (not statistically significant). The ICP/MAP ratio was 0.341±0.015 in the TRT group and 0.274±0.049 in the control group (not statistically significant). The median subcutaneous fat cell size was 4.85×10³ (range 0.85–12.53×10³) μm² in the control group and 4.93×10³ (range 6.42–19.7×10³) μm² in the TRT group (not statistically significant). In contrast, median visceral fat cell size was significantly smaller in the TRT group (4.93×10³ μm² [range 0.51–14.88×10³]) than in the control group (6.08×10³ μm² [0.77–19.97×10³]; P<0.001, Mann-Whitney U test).

Conclusion

This is the first study clearly indicating that TRT can decrease visceral fat cell size, which is a key modulator in the metabolic syndrome. However, a short course of TRT could not improve the ICP response in hypogonadal aged male rats. Further investigation is necessary to clarify the exact rationale of TRT on the visceral fat cell.

Free testosterone by direct and calculated measurement versus equilibrium dialysis in a clinical population

INTRODUCTION

The value of clinically available free testosterone (FT) assays remains controversial. Here, we evaluate the agreement between the radioimmunoassay (RIA) and calculated FT (cFT) versus equilibrium dialysis (EqD), considered the gold standard.

METHODS

Fifty-six consecutive men (aged 26-77) had blood samples assessed for FT, including men with treated and untreated testosterone deficiency (TD) and men without TD. Samples were split and tested by the two methodologies at a Quest Diagnostics national reference laboratory. cFT was calculated by the Vermeulen method.

RESULTS

A robust correlation was noted for RIA and EqD (r = 0.966) and for cFT and EqD (r = 0.986). Strong correlations were observed for men receiving testosterone therapy and for men in the lowest and highest quartiles for total and FT. The correlation of total testosterone with FT was similar for cFT (r = 0.843), RIA (r = 0.806), and EqD (r = 0.809). Sex-hormone binding globulin (SHBG) was not correlated with any measure of FT. Bland-Altman analysis demonstrated similar bias for both cFT and RIA, although cFT consistently overestimated FT. Numerical values for RIA were approximately one seventh of EqD values.

CONCLUSIONS

These results support the clinical use of both RIA and cFT as measures of FT. Due to numerical differences, each test requires its own set of reference values.

A randomized, double-blind, placebo-controlled trial of testosterone gel on body composition and health-related quality-of-life in men with hypogonadal to low-normal levels of serum testosterone and symptoms of androgen deficiency over 6 months with 12 months open-label follow-up

INTRODUCTION

The clinical significance of low to low-normal testosterone (T) levels in men remains debated.

AIM

To analyze the effects of raising serum T on lean body mass (LBM), fat mass (FM), total body mass, and health-related quality-of-life (HRQoL).

METHODS

Randomized, double-blind, placebo-controlled study. Men, aged 50-80 years, with serum total T<15 nmol/L and bioavailable T < 6.68 nmol/L, and a Aging Males' Symptoms (AMS) total score >36, received 6 months treatment with transdermal 1% T gel (5-7.5 mg/day; n =183) or placebo gel (n =179), followed by 12 months open-label with T in all.

RESULTS

After 6 months, LBM increased in T- treated patients by 1.28 ± 0.15 kg (mean ± SE) and FM decreased by 1.16 ± 0.16 kg, with minor changes with placebo (LBM +0.02 ± 0.10 kg and FM -0.14 ± 0.12 kg; all p < 0.001, T group vs. placebo). Changes were largely similar across subgroups of age, baseline total testosterone, and baseline BMI. Total HRQoL improved compared with placebo (p < 0.05, T group vs. placebo).

CONCLUSIONS

Six months 1% T gel improved body composition and HRQoL in symptomatic men with low to low-normal T, with further improvements over the following 12 months.