Is the haematopoietic effect of testosterone mediated by erythropoietin? The results of a clinical trial in older men

The stimulatory effects of testosterone on erythropoiesis are very well known, but the mechanisms underlying the erythropoietic action of testosterone are still poorly understood, although erythropoietin has long been considered a potential mediator. A total of 108 healthy men >65 years old with serum testosterone concentration <475 ng/dL were recruited by direct mailings to alumni of the University of Pennsylvania and Temple University, and randomized to receive a 60-cm(2) testosterone or placebo patch for 36 months. Ninety-six subjects completed the trial. We used information and stored serum specimens from this trial to test the hypothesis that increasing testosterone increases haemoglobin by stimulating erythropoietin production. We used information of 67 men, 43 in the testosterone group and 24 in the placebo group who had banked specimens available for assays of testosterone, haemoglobin and erythropoietin at baseline and after 36 months. The original randomized clinical study was primarily designed to verify the effects of testosterone on bone mineral density. The primary outcome of this report was to investigate whether or not transdermal testosterone increases haemoglobin by increasing erythropoietin levels. The mean age ± SD of the 67 subjects at baseline was 71.8 ± 4.9 years. Testosterone replacement therapy for 36 months, as compared with placebo, induced a significant increase in haemoglobin (0.86 ± 0.31 g/dL, p = 0.01), but no change in erythropoietin levels (-0.24 ± 2.16 mIU/mL, p = 0.91). Included time-varying measure of erythropoietin did not significantly account for the effect of testosterone on haemoglobin (Treatment-by-time: β = 0.93, SE = 0.33, p = 0.01). No serious adverse effect was observed. Transdermal testosterone treatment of older men for 36 months significantly increased haemoglobin, but not erythropoietin levels. The haematopoietic effect of testosterone does not appear to be mediated by stimulation of erythropoietin production.

Effect of transdermal testosterone treatment on serum lipid and apolipoprotein levels in men more than 65 years of age

PURPOSE

Because the effects of androgen replacement on lipoprotein levels are uncertain, we sought to determine the effect of transdermal testosterone treatment on serum lipid and apolipoprotein levels in elderly men.

SUBJECTS AND METHODS

One hundred and eight healthy men more than 65 years of age who had serum testosterone concentrations >1 SD below the mean for young men were randomly assigned to receive either testosterone (54 men; 6 mg/day) or placebo (54 men) transdermally in a double-blind fashion for 36 months. Serum concentrations of lipids and apolipoproteins were measured, and cardiovascular events recorded.

RESULTS

Serum total cholesterol concentrations decreased in both the testosterone-treated men and placebo-treated men, but the 3-year mean (+/- SD) decreases in the two groups (testosterone treated, -17 +/- 29 mg/dL; placebo treated, -12 +/- 38 mg/dL) were not significantly different from each other (P = 0.4). Similarly, serum low-density lipoprotein (LDL) cholesterol levels decreased in both treatment groups, but the decreases in the two groups (testosterone treated, -16 +/- 24 mg/dL; placebo treated, -16 +/- 33 mg/dL) were similar (P = 1.0). Levels of high-density lipoprotein (HDL) cholesterol, triglycerides, and apolipoproteins A-I and B did not change. Lipoprotein(a) levels increased in both groups by similar amounts (testosterone treated, 3 +/- 9 mg/dL; placebo treated, 4 +/- 6 mg/dL; P = 1.0). The number of cardiovascular events was small and did not differ significantly between the testosterone-treated men (9 events) and the placebo-treated men (5 events) during the 3-year study (relative risk = 1.8; 95% confidence interval: 0.7 to 5.0).

CONCLUSIONS

As compared with placebo, transdermal testosterone treatment of healthy elderly men for 3 years did not affect any of the lipid or apolipoprotein parameters that we measured. The effect of testosterone treatment on cardiovascular events was unclear, because the number of events was small.

Effects of testosterone replacement in hypogonadal men

Treatment of hypogonadal men with testosterone has been shown to ameliorate the effects of testosterone deficiency on bone, muscle, erythropoiesis, and the prostate. Most previous studies, however, have employed somewhat pharmacological doses of testosterone esters, which could result in exaggerated effects, and/or have been of relatively short duration or employed previously treated men, which could result in dampened effects. The goal of this study was to determine the magnitude and time course of the effects of physiological testosterone replacement for 3 yr on bone density, muscle mass and strength, erythropoiesis, prostate volume, energy, sexual function, and lipids in previously untreated hypogonadal men. We selected 18 men who were hypogonadal (mean serum testosterone +/- SD, 78 +/- 77 ng/dL; 2.7 +/- 2.7 nmol/L) due to organic disease and had never previously been treated for hypogonadism. We treated them with testosterone transdermally for 3 yr. Sixteen men completed 12 months of the protocol, and 14 men completed 36 months. The mean serum testosterone concentration reached the normal range by 3 months of treatment and remained there for the duration of treatment. Bone mineral density of the lumbar spine (L2-L4) increased by 7.7 +/- 7.6% (P < 0.001), and that of the femoral trochanter increased by 4.0 +/- 5.4% (P = 0.02); both reached maximum values by 24 months. Fat-free mass increased 3.1 kg (P = 0.004), and fat-free mass of the arms and legs individually increased, principally within the first 6 months. The decrease in fat mass was not statistically significant. Strength of knee flexion and extension did not change. Hematocrit increased dramatically, from mildly anemic (38.0 +/- 3.0%) to midnormal (43.1 +/- 4.0%; P = 0.002) within 3 months, and remained at that level for the duration of treatment. Prostate volume also increased dramatically, from subnormal (12.0 +/- 6.0 mL) before treatment to normal (22.4 +/- 8.4 mL; P = 0.004), principally during the first 6 months. Self-reported sense of energy (49 +/- 19% to 66 +/- 24%; P = 0.01) and sexual function (24 +/- 20% to 66 +/- 24%; P < 0.001) also increased, principally within the first 3 months. Lipids did not change. We conclude from this study that replacing testosterone in hypogonadal men increases bone mineral density of the spine and hip, fat-free mass, prostate volume, erythropoiesis, energy, and sexual function. The full effect of testosterone on bone mineral density took 24 months, but the full effects on the other tissues took only 3-6 months. These results provide the basis for monitoring the magnitude and the time course of the effects of testosterone replacement in hypogonadal men.

Effect of testosterone treatment on body composition and muscle strength in men over 65 years of age

As men age, serum testosterone concentrations decrease, the percentage of body mass that is fat increases, the percentage of lean body mass decreases, and muscle strength decreases. Because these changes are similar to those that occur in hypogonadal men, we hypothesized that increasing the serum testosterone concentration of men over 65 yr of age to that in young men would decrease their fat mass, increase their lean mass, and increase their muscle strength. We randomized 108 men over 65 yr of age to wear either a testosterone patch or a placebo patch in a double blind study for 36 months. We measured body composition by dual energy x-ray absorptiometry and muscle strength by dynamometer before and during treatment. Ninety-six men completed the entire 36-month protocol. Fat mass decreased (-3.0+/-0.5 kg) in the testosterone-treated men during the 36 months of treatment, which was significantly different (P = 0.001) from the decrease (-0.7+/-0.5 kg) in the placebo-treated men. Lean mass increased (1.9+/-0.3 kg) in the testosterone-treated men, which was significantly different (P < 0.001) from that (0.2+/-0.2 kg) in the placebo-treated men. The decrease in fat mass in the testosterone-treated men was principally in the arms (-0.7+/-0.1 kg; P < 0.001 compared to the placebo group) and legs (-1.1+/-0.2 kg; P < 0.001), and the increase in lean mass was principally in the trunk (1.9+/-0.3 kg; P < 0.001). The change in strength of knee extension and flexion at 60 degrees and 180 degrees angular velocity during treatment, however, was not significantly different between the two groups. We conclude that increasing the serum testosterone concentrations of normal men over 65 yr of age to the midnormal range for young men decreased fat mass, principally in the arms and legs, and increased lean mass, principally in the trunk, but did not increase the strength of knee extension and flexion, as measured by dynamometer.

Effect of testosterone treatment on bone mineral density in men over 65 years of age

As men age, their serum testosterone concentrations decrease, as do their bone densities. Because bone density is also low in hypogonadal men, we hypothesized that increasing the serum testosterone concentrations of men over 65 yr to those found in young men would increase their bone densities. We randomized 108 men over 65 yr of age to wear either a testosterone patch or a placebo patch double blindly for 36 months. We measured bone mineral density by dual energy x-ray absorptiometry before and during treatment. Ninety-six men completed the entire 36-month protocol. The mean serum testosterone concentration in the men treated with testosterone increased from 367 +/- 79 ng/dL (+/-SD; 12.7 +/- 2.7 nmol/L) before treatment to 625 +/- 249 ng/dL (21.7 +/- 8.6 nmol/L; P < 0.001) at 6 months of treatment and remained at that level for the duration of the study. The mean bone mineral density of the lumbar spine increased (P < 0.001) in both the placebo-treated (2.5 +/- 0.6%) and testosterone-treated (4.2 +/- 0.8%) groups, but the mean changes did not differ between the groups. Linear regression analysis, however, demonstrated that the lower the pretreatment serum testosterone concentration, the greater the effect of testosterone treatment on lumbar spine bone density from 0-36 months (P = 0.02). This analysis showed a minimal effect (0.9 +/- 1.0%) of testosterone treatment on bone mineral density for a pretreatment serum testosterone concentration of 400 ng/dL (13.9 nmol/L), but an increase of 5.9 +/- 2.2% for a pretreatment testosterone concentration of 200 ng/dL (6.9 nmol/L). Increasing the serum testosterone concentrations of normal men over 65 yr of age to the midnormal range for young men did not increase lumbar spine bone density overall, but did increase it in those men with low pretreatment serum testosterone concentrations.