Testosterone treatment for the aging man: the controversy

Can testosterone level be a good predictor of late-onset hypogonadism?

Androgens are essential for the development and growth of the genitalia. They regulate the erectile physiology by multiple mechanisms. Several studies have examined associations among sex hormones' serum levels, erectile function and sex drive. We sought to identify a protocol for using testosterone in men with erectile dysfunction and late-onset hypogonadism (LOH). During a 16-month period, men with erectile dysfunction who presented to the andrology clinic were selected. They underwent a complete physical examination and filled out the International Index of Erectile Function-5 questionnaire. Serum luteinising hormone (LH) and testosterone levels were evaluated. Patients received a single intramuscular injection of 250 mg testosterone. Thereafter, serum levels of LH and testosterone were measured 3 weeks later. The mean age was 53 years old. After treating patients with testosterone, 45 (94%) showed improvement in LOH symptoms including libido, loss of energy, irritability and quality of life. The mean International Index of Erectile Function was 9 and 13.1, prior to and after treatment respectively. Mean serum testosterone levels before and after treatment were 4.2 and 4.1 ng ml(-1) respectively (P = 0.849). Mean serum LH revealed a significant decrease after the study (P = 0.004) (6.12 and 5.1 ng ml(-1) , before and after the study respectively). Our findings suggested that testosterone replacement therapy improves libido and LOH symptoms in individuals with almost normal or lower limit normal value of serum testosterone levels.

A safety study of administration of parenteral testosterone undecanoate to elderly men over minimally 24 months

This study investigated the safety of administration of long-acting parenteral testosterone undecanoate (TU) to 122 hypogonadal, mainly elderly men, aged 59.6 ± 8.0 years (range 18-83 years old), with baseline testosterone levels between 5.8 and 12.1 nmol l(-1) (mean ± SD = 9.3 ± 1.7). Patients were followed for 24 months. Plasma testosterone rose from 9.3 ± 1.7 to 14.9 ± 4.5 nmol l(-1) (P< 0.01) at 3 months, then stabilised at 19.2 ± 4.6 nmol l(-1) after 6 months. International Prostate Symptoms Scores and Residual Bladder Volumes decreased significantly (P <0.01) over the study period. Prostate volume and prostate-specific antigen levels fluctuated over the study period but had not increased significantly after 24 month. Haemoglobin concentrations increased significantly (P < 0.001) over the 24 months while the haematocrit increased significantly (P < 0.001) during the first 15 months and then levelled off. Statistical analysis with expressing values as means ± SD masks excesses above reference values of individual patients. These excesses were noted in low numbers, were permanently present in some but not in other individuals, and did not increase in number over the 24 month study period. Over 24 months treatment with TU appeared acceptably safe, but longer and larger scale studies are needed.

The role of testosterone in the etiology and treatment of obesity, the metabolic syndrome, and diabetes mellitus type 2

Obesity has become a major health problem. Testosterone plays a significant role in obesity, glucose homeostasis, and lipid metabolism. The metabolic syndrome is a clustering of risk factors predisposing to diabetes mellitus type 2, atherosclerosis, and cardiovascular morbidity and mortality. The main components of the syndrome are visceral obesity, insulin resistance, glucose intolerance, raised blood pressure and dyslipidemia (elevated triglycerides, low levels of high-density lipoprotein cholesterol), and a proinflammatory and thrombogenic state. Cross-sectional epidemiological studies have reported a direct correlation between plasma testosterone and insulin sensitivity, and low testosterone levels are associated with an increased risk of type 2 diabetes mellitus, dramatically illustrated by androgen deprivation in men with prostate carcinoma. Lower total testosterone and sex hormone-binding globulin (SHBG) predict a higher incidence of the metabolic syndrome. Administration of testosterone to hypogonadal men reverses part of the unfavorable risk profile for the development of diabetes and atherosclerosis.

Androgens and male aging: Current evidence of safety and efficacy

Many signs of aging, such as sexual dysfunction, visceral obesity, impaired bone and muscle strength, bear a close resemblance to features of hypogonadism in younger men. The statistical decline of serum testosterone in aging men is solidly documented. It has been presumed that the above features of aging are related to the concurrent decline of androgens, and that correction of the lower-than-normal circulating levels of testosterone will lead to improvement of symptoms of aging. But in essence, the pivotal question whether the age-related decline of testosterone must be viewed as hypogonadism, in the best case reversed by testosterone treatment, has not been definitively resolved. Studies in elderly men with lower-than-normal testosterone report improvement of features of the metabolic syndrome, bone mineral density, of mood and of sexual functioning. But as yet there is no definitive proof of the beneficial effects of restoring testosterone levels to normal in elderly men on clinical parameters. Few of these studies meet as yet rigorous standards of scientific enquiry: double-blind, placebo-controlled design of the study. The above applies also to the assessment of safety of testosterone administration to elderly men. There is so far no convincing evidence that testosterone is a main factor in the development of prostate cancer in elderly men and guidelines for monitoring the development of prostate disease have been developed. It is of note that there are presently no long-term safety data with regard to the prostate. Polycythemia is another potential complication of testosterone treatment. It is dose dependent and can be managed with dose adjustment.

The associations between serum sex hormones, erectile function, and sex drive: the Olmsted County Study of Urinary Symptoms and Health Status among Men

INTRODUCTION

Testosterone replacement therapy has been used in the treatment of sexual dysfunction; however, its use remains controversial, and the effectiveness and long-term health implications are unknown.

AIM

To evaluate the association between sex hormone serum levels, erectile function, and sexual drive in a population-based sample of men.

METHODS

A stratified random sample of men residing in Olmsted County, Minnesota, completed a questionnaire containing questions from the Brief Male Sexual Function Inventory (BMSFI), and participated in a clinical exam, which included serum hormone measurements.

MAIN OUTCOME MEASURES

Levels of sexual drive (libido) and erectile function as assessed by the BMSFI and serum testosterone, bioavailable testosterone, and estradiol measurements.

RESULTS

Out of 414 men, 294 had a regular sexual partner and androgen measurements at the 14th year of follow-up. Total testosterone and erectile function were significantly correlated even after adjustment for age (r = 0.12, P = 0.04). Conversely, total testosterone was not significantly correlated with sex drive (r = 0.08, P = 0.17). Bioavailable testosterone was significantly correlated with both erectile function and sex drive (r = 0.16, P = 0.01 and r = 0.20, P = 0.001, respectively). However, these associations disappeared after age adjustment (r = 0.04 and r = 0.09).

CONCLUSIONS

These cross-sectional results suggest the relationship between sex hormones and sexual function is complex, and that the age-related decline in sexual function may be due to age-related declines in levels of bioavailable testosterone rather than total testosterone levels.

Testosterone replacement therapy and prostate cancer: A word of caution

The number of men for whom testosterone is prescribed is rapidly increasing. The aging man normally demonstrates a gradual decline in testosterone. Symptoms of hypogonadism include erectile dysfunction, diminished libido, sarcopenia, increased adiposity, osteopenia and osteoporosis, impaired cognition, and depression. There is a paucity of data regarding both efficacy and safety of testosterone replacement therapy. Testosterone levels have been shown to modulate prostate cancer risk and progression. A prospective evaluation of prostate cancer risk with testosterone replacement therapy has not been conducted. We outline concerns and recommendations for the use of testosterone replacement therapy in the aging man.

Recent insights into androgen action on the anatomical and physiological substrate of penile erection

Erectile response is centrally and peripherally regulated by androgens. The original insights into the mechanisms of action of androgens were that androgens particularly exert effects on libido and that erections in response to erotic stimuli were relatively androgen-independent. It was shown that sexual functions in men required androgen levels at the low end of reference values of testosterone. So it seemed that testosterone was not useful treatment for men with erectile difficulties, particularly following the advent of the phosphodiesterase type 5 (PDE5) inhibitors. However, approximately 50% of those treated with PDE5 inhibitors discontinue their treatment. A number of recent developments shed new light on testosterone treatment of erectile dysfunction (ED) in aging men. (1) A recent insight is that, in contrast to younger men, elderly men might require higher levels of testosterone for normal sexual functioning. (2) Several studies have indicated that PDE5 inhibitors are not always sufficient to restore erectile potency in men, and that testosterone improves the therapeutical response to PDE5 inhibitors considerably. (3) There is growing insight that testosterone has profound effects on tissues of the penis involved in the mechanism of erection and that testosterone deficiency impairs the anatomical and physiological substrate of erectile capacity, reversible upon androgen replacement. The synthesis of PDE5 is upregulated by androgens, and the arterial inflow into the penis is improved by giving androgen. The above invites a re-examination of the merits of giving testosterone to aging men with ED. The beneficial effects of PDE5 inhibitors may only be optimally expressed in a eugonadal environment.