Age trends in the level of serum testosterone and other hormones in middle-aged men: longitudinal results from the Massachusetts male aging study

Long-term stability of maternal prenatal steroid hormones from the National Collaborative Perinatal Project: still valid after all these years

Large epidemiological samples, including the National Collaborative Perinatal Project (NCPP), in which blood/serum was collected during pregnancy and offspring followed longitudinally, offer the unique opportunity to examine neuroendocrine mechanisms underlying prenatal "programming" of adult health and disease. However, in order to conduct longitudinal analyses, it is critical to determine the validity of maternal prenatal samples stored over long periods. We investigated the validity of cortisol, testosterone, and their binding globulins (corticosteroid-binding globulin (CBG) and sex hormone-binding globulin (SHBG)) in maternal prenatal serum from the NCPP after over 40 years of storage. Study 1 included 64 maternal serum samples collected on the day of delivery; study 2 involved 1099 third trimester serum samples collected between gestational weeks 31 and 36. Across both studies, cortisol and testosterone concentrations were consistent with values from published studies of fresh samples collected at similar points in gestation. CBG and SHBG were present, but showed some differences from published studies. Results support the validity of cortisol and testosterone values following 40+ years of storage. Results also provide validation for future longitudinal tests of prenatal "programming" hypotheses within the NCPP. Stability of steroid hormones over decades suggests that stored samples from other longitudinal studies may also allow opportunities to investigate links between prenatal steroids and long-term offspring outcomes.

The relative contributions of aging, health, and lifestyle factors to serum testosterone decline in men

CONTEXT

Although it is known that serum testosterone (T) concentrations decline with age, the relative contributions of changes in health and lifestyle to that decline have not been adequately assessed.

OBJECTIVE

The objective of this study was to establish the relative importance of aging, health, and lifestyle in contributing to male T decline.

DESIGN

A prospective cohort study of health and endocrine functioning in randomly selected men with a baseline visit (T1, 1987-1989) and two follow-up visits (T2, 1995-1997; T3, 2002-2004) was conducted.

SETTING

An observational study of men residing in greater Boston, Massachusetts, was conducted.

PARTICIPANTS

Participants included 1667 men aged 40 to 70 at baseline; follow-up was conducted on 947 (57%) and 584 (35%) at T2 and T3, respectively.

MAIN OUTCOME MEASURES

Main outcome measures included total serum T, calculated free T (FT), and SHBG.

RESULTS

There were substantial declines in total serum T and FT levels associated with aging alone. However, many health and lifestyle changes were associated with accelerated decline. A 4- to 5-kg/m2 increase in body mass index or loss of spouse was associated with declines in total serum T comparable to that associated with approximately 10 yr of aging. Results were similar for FT, but fewer factors were associated with SHBG after age was taken into account.

CONCLUSIONS

Both chronological aging and changes in health and lifestyle factors are associated with declines in serum T. Comorbidities and lifestyle influences may be as strongly associated with declining T levels as is aging itself over the short- to midterm. These results suggest the possibility that age-related hormone decline may be decelerated through the management of health and lifestyle factors.

The association between obesity and the diagnosis of androgen deficiency in symptomatic ageing men

OBJECTIVE

To determine the influence of obesity on the diagnosis of age-related androgen deficiency (AD) in symptomatic men according to current Australian guidelines.

DESIGN, SETTING AND PARTICIPANTS

A community-based cohort of healthy ageing men with symptoms suggestive of AD was studied between May 2001 and February 2003. Men were classified as obese or non-obese according to body mass index (BMI) or waist circumference (WC).

MAIN OUTCOME MEASURE

Diagnosis of AD according to Endocrine Society of Australia (ESA) guidelines.

RESULTS

223 men aged 54-86 years with mean BMI 27.3 +/- 0.2 kg/m2 (range 20.5-36.2 kg/m2) were recruited; 99 men were obese (BMI > or = 30.0 kg/m2 or WC > or = 102 cm) and 124 men were non-obese. Obese men had lower total testosterone (TT) (12.7 +/- 0.4 v 15.0 +/- 0.4 nmol/L); P < 0.001) and calculated free testosterone (275.7 +/- 7.8 v 299.3 +/- 7.4 pmol/L); P = 0.03) levels than non-obese men. TT levels < 8 nmol/L were recorded in 12% of obese men and 1% of non-obese men. Applying the ESA guidelines for the diagnosis of age-related AD, 15 obese men (15%) and 4 non-obese men (3%) were classified as being eligible for androgen therapy supported by the Pharmaceutical Benefits Scheme (PBS); the relative risk in obese men was 1.92 (95% CI, 1.44-2.55; P < 0.001).

CONCLUSION

Obesity is an important determinant of serum TT levels in ageing men. Almost one in seven obese men but only one in 30 non-obese men in our study were eligible for PBS-supported androgen therapy according to Australian guidelines. Although obese men are more likely to have biochemical hypoandrogenism, the clinical implications of this remain uncertain. Studies of testosterone therapy in this group of ageing men are needed to determine whether androgen replacement is beneficial.

A population-level decline in serum testosterone levels in American men

CONTEXT

Age-specific estimates of mean testosterone (T) concentrations appear to vary by year of observation and by birth cohort, and estimates of longitudinal declines in T typically outstrip cross-sectional decreases. These observations motivate a hypothesis of a population-level decrease in T over calendar time, independent of chronological aging.

OBJECTIVE

The goal of this study was to establish the magnitude of population-level changes in serum T concentrations and the degree to which they are explained by secular changes in relative weight and other factors.

DESIGN

We describe a prospective cohort study of health and endocrine functioning in randomly selected men of age 45-79 yr. We provide three data collection waves: baseline (T1: 1987-1999) and two follow-ups (T2: 1995-1997, T3: 2002-2004).

SETTING

This was an observational study of randomly selected men residing in greater Boston, Massachusetts.

PARTICIPANTS

Data obtained from 1374, 906, and 489 men at T1, T2, and T3, respectively, totaling 2769 observations taken on 1532 men.

MAIN OUTCOME MEASURES

The main outcome measures were serum total T and calculated bioavailable T.

RESULTS

We observe a substantial age-independent decline in T that does not appear to be attributable to observed changes in explanatory factors, including health and lifestyle characteristics such as smoking and obesity. The estimated population-level declines are greater in magnitude than the cross-sectional declines in T typically associated with age.

CONCLUSIONS

These results indicate that recent years have seen a substantial, and as yet unrecognized, age-independent population-level decrease in T in American men, potentially attributable to birth cohort differences or to health or environmental effects not captured in observed data.

Erectile dysfunction and hypogonadism among men with HIV

Erectile dysfunction (ED) and hypogonadism are increasingly recognized conditions, however, the prevalence and etiologies of these conditions among HIV-infected men remain unclear. We studied 300 HIV-infected men who completed standardized questionnaires regarding sexual function and hypogonadal symptoms. An early morning testosterone test was performed; patients with a low serum testosterone level (defined by <300 ng/dL), underwent additional blood tests to determine the etiology of the hypogonadism. The participants' mean age was 39 years (range, 19-72); 61% were Caucasian; 24%, African American; 9%, Hispanic; and 5% other. Participants had been HIV-positive for a mean of 9 years (range, 0.5-20) with a mean CD4 count of 522 cells/mm(3) (range, 1-1531). Sixty percent were receiving antiretroviral therapy. ED was reported by 61.4%; of those with ED, 32% did not have a rigid enough erection for penetration, and 46% were unable to sustain an erection for the completion of intercourse. In the multivariate analysis, increasing age (odds ratio [OR] 1.4 for a 5-year increment, p < 0.001) and depression (OR 2.64, p < 0.0001) were associated with ED. A higher current CD4 count was protective (OR 0.80 for each 100 cells/mm(3), p = 0.004). Only 25% of patients with ED had utilized a phosphodiesterase-5-inhibitor for treatment. Seventeen percent of the 300 men were hypogonadal; there was no correlation between hypogonadism and ED. Increasing age and a higher body mass index (BMI) were positively associated with hypogonadism, while smoking was negatively associated (OR 0.44, p = 0.02). All patients with low testosterone had secondary hypogonadism. There was no association between ED or hypogonadism with the current, past, or cumulative use of HIV medications.

The ageing male reproductive tract

Ageing of the male reproductive system is characterized by changes in the endocrine system, hypogonadism, erectile dysfunction and proliferative disorders of the prostate gland. Stochastic damage accumulating within ageing leads to progressive dysregulation at each level of the hypothalamic-pituitary-gonadal (HPG) axis and in local auto/paracrine interactions, thereby inducing morphological changes in reproductive target organs, such as the prostate, testis and penis. Despite age-related changes in the HPG axis, endocrine functions are generally sufficient to maintain fertility in elderly men. Ageing of the male reproductive system can give rise to clinically relevant manifestations, such as benign prostatic hyperplasia (BPH), prostate cancer (PCa) and erectile dysfunction (ED). In this review, we discuss morphological/histological changes occurring in these organs and current views and concepts of the underlying pathology. Moreover, we emphasize the molecular/cellular pathways leading to reduced testicular/penile function and proliferative disorders of the prostate gland.

Age related variation of salivary testosterone values in healthy Japanese males

OBJECTIVE

We examined age associated variation in salivary testosterone values among Japanese males as well as anthropometric measurements.

METHODS

Salivary samples were collected in pretreated sodium azide treated tubes. The first series: 15-79-year-old males (n = 99); two morning and two evening samples were collected at home for two days. The second series: 90-year-old males (n = 29); one morning sample was collected. Testosterone values were determined using an iodine125-based radioimmunoassay kit modified for saliva.

RESULTS

Results show 1) a significant decrease in salivary testosterone values from 20s to 40s and older, 2) no significant decline after 40 through 90 years old, 3) no significant age-related differences in the degree of intraindividual diurnal fluctuation across age groups of 40-70s, and 4) higher BMI is associated with the lower salivary testosterone among 40-70s.

CONCLUSIONS

These results suggest that neither a constant decrease of salivary testosterone values or markedly reduced intraindividual fluctations are universal aspects of aging. Older males may maintain relatively high testosterone levels compared to younger men and a relatively 'robust' neuroendocrinological system.

The male biological clock

Do men have biological clocks that affect their hormone levels, fertility, and the genetic quality of their sperm? Women can no longer be viewed as solely responsible for age-related fertility and genetic problems. The effects of andropause and advanced paternal age on fertility and offspring are still under investigation. Further research is needed to fully characterize the associated risks and to treat the underlying abnormalities. A better understanding of the cellular and biochemical mechanisms of "gonadal" aging is important in order to determine safe, effective ways to delay this process and "rewind" the male biological clock. The benefits may include decreasing the potential for adverse genetic consequences in offspring, improvement in the sexual and reproductive health of aging males, and increase a woman's chance of having healthy children by correcting defects in the male reproductive system.

Association of specific symptoms and metabolic risks with serum testosterone in older men

CONTEXT

Although attention and concern about health disorders in aging men have been growing, the structure of psychological and somatic complaints of actual patients, not population-based cohorts, has not been elucidated in relation to sex hormone patterns and metabolism.

OBJECTIVE

The objective of the study was investigation of factors influencing complaint structures in aging male patients.

DESIGN

This was a cross-sectional cohort study.

SETTING

The study was conducted in an andrological outpatient department.

PATIENTS

Subjects included 434 consecutive male patients aged 50-86 yr.

MAIN OUTCOME MEASURES

The following hypotheses were measured: 1) psychosomatic complaints and metabolic factors in aging male patients are related to sex hormone levels in a symptom-specific manner, and 2) patients form subcohorts.

RESULTS

A clear-cut threshold for late-onset hypogonadism was not found; rather, prevalence of psychosomatic symptoms and metabolic risk factors accumulated with decreasing androgen levels. For example, androgen-induced prevalence of loss of libido or vigor increased below testosterone concentrations of 15 nmol/liter (P < 0.001), whereas depression and diabetes mellitus type 2 (also in nonobese men) were significantly more present in men with testosterone concentrations below 10 nmol/liter (P < 0.001). Erectile dysfunction was identified as a composite pathology of metabolic risk factors, smoking, and depressivity, whereas only testosterone concentrations below 8 nmol/liter contributed to that symptom (P = 0.003). Cluster analysis revealed aging men to present within three independent groups characterized by psychosomatic complaints, metabolic disorders, and sexual health problems. These subgroups of patients exhibit distinct features in terms of androgen levels, age, and body mass index.

CONCLUSIONS

There is no evidence that a uniform structure of testosterone concentrations and complaints exists within the cohort of elderly male patients. Rather, in aging male patients, psychosomatic complaints and metabolic risk relate to testosterone in a symptom-specific manner.

Differences in the apparent metabolic clearance rate of testosterone in young and older men with gonadotropin suppression receiving graded doses of testosterone

BACKGROUND

Recently we found that testosterone levels are higher in older men than young men receiving exogenous testosterone. We hypothesized that older men have lower apparent testosterone metabolic clearance rates (aMCR-T) that contribute to higher testosterone levels.

OBJECTIVE

The objective of the study was to compare aMCR-T in older and young men and identify predictors of aMCR-T.

METHODS

Sixty-one younger (19-35 yr) and 60 older (59-75 yr) men were given a monthly GnRH agonist and weekly testosterone enanthate (TE) (25, 50, 125, 300, or 600 mg) for 5 months. Estimated aMCR-T was calculated from the amount of TE delivered weekly and trough serum testosterone concentrations, corrected for real-time absorption kinetics from the im testosterone depot.

RESULTS

Older men had lower total (316 +/- 13 vs. 585 +/- 26 ng/dl, P < 0.00001) and free testosterone (4 +/- 0.1 vs. 6 +/- 0.3 ng/dl, P < 0.00001) and higher SHBG (52 +/- 3 vs. 33 +/- 2 nmol/liter, P < 0.00001) than younger men at baseline. Total and free testosterones increased with TE dose and were higher in older men than young men in the 125-, 300-, and 600-mg dose groups. aMCR-T was lower in older men than young men (1390 +/- 69 vs. 1821 +/- 102 liter/d, P = 0.006). aMCR-T correlated negatively with age (P = 0.0007), SHBG (P = 0.046), and total testosterone during treatment (P = 0.02) and percent body fat at baseline (P = 0.01) and during treatment (P = 0.004). aMCR-T correlated positively with lean body mass at baseline (P = 0.03) and during treatment (P = 0.01). In multiple regression models, significant predictors of aMCR-T included lean body mass (P = 0.008), percent fat mass (P = 0.009), and SHBG (P = 0.001).

CONCLUSIONS

Higher testosterone levels in older men receiving TE were associated with an age-related decrease in apparent testosterone metabolic clearance rates. Body composition and SHBG were significant predictors of aMCR-T.

Anabolic deficiency in men with chronic heart failure: prevalence and detrimental impact on survival

BACKGROUND

The age-related decline of circulating anabolic hormones in men is associated with increased morbidity and mortality. We studied the prevalence and prognostic consequences of deficiencies in circulating total testosterone (TT) and free testosterone, dehydroepiandrosterone sulfate (DHEAS), and insulin-like growth factor-1 (IGF-1) in men with chronic heart failure (CHF).

METHODS AND RESULTS

Serum levels of TT, DHEAS, and IGF-1 were measured with immunoassays in 208 men with CHF (median age 63 years; median left ventricular ejection fraction 33%; New York Heart Association class I/II/III/IV, 19/102/70/17) and in 366 healthy men. Serum levels of free testosterone were estimated (eFT) from levels of TT and sex hormone binding globulin. Deficiencies in DHEAS, TT, eFT, and IGF-1, defined as serum levels at or below the 10th percentile of healthy peers, were seen across all age categories in men with CHF. DHEAS, TT, and eFT were inversely related to New York Heart Association class irrespective of cause (all P<0.01). DHEAS correlated positively with left ventricular ejection fraction and inversely with N-terminal pro-brain natriuretic peptide (both P<0.01). Circulating TT, eFT, DHEAS, and IGF-1 levels were prognostic markers in multivariable models when adjusted for established prognostic factors (all P<0.05). Men with CHF and normal levels of all anabolic hormones had the best 3-year survival rate (83%, 95% CI 67% to 98%) compared with those with deficiencies in 1 (74% survival rate, 95% CI 65% to 84%), 2 (55% survival rate, 95% CI 45% to 66%), or all 3 (27% survival rate, 95% CI 5% to 49%) anabolic endocrine axes (P<0.0001).

CONCLUSIONS

In male CHF patients, anabolic hormone depletion is common, and a deficiency of each anabolic hormone is an independent marker of poor prognosis. Deficiency of >1 anabolic hormone identifies groups with a higher mortality.

Changes in BMI modulate age-associated changes in sex hormone binding globulin and total testosterone, but not bioavailable testosterone in young adult men: the CARDIA Male Hormone Study

OBJECTIVES

To compare age-associated 8-year changes in total testosterone, calculated bioavailable testosterone and sex hormone binding globulin (SHBG) across five groups of men stratified according to change in body mass index (BMI) (i.e., BMI stable (+/-0.69 kg/m(2)), decreased (-0.7 kg/m(2)), increased minimally (0.7-1.74 kg/m(2)), increased moderately (1.75-3.19 kg/m(2)) and increased most (> or =3.20 kg/m(2))).

DESIGN

Eight-year longitudinal cohort study.

SUBJECTS

Four hundred and seventy-four black and 695 white men, aged 24-31 years at the time of the first hormone measurement.

MEASUREMENTS

Aging-related changes in serum SHBG, total testosterone and bioavailable testosterone.

RESULTS

SHBG significantly increased with age for men whose BMI decreased, and there were progressively smaller increases for men whose BMI was stable, or whose BMI increased minimally or moderately (range 1.1-0.3 nM per year, P< or =0.03, respectively). There was no age relationship with SHBG among men whose BMI increased most. Total testosterone did not change with age for men whose BMI decreased, was stable or increased minimally, but for men whose BMI increased moderately and most there was a graded decrease in total testosterone with age (beta=-0.2 and -0.4 nM per year, respectively, P< or =0.005). However, bioavailable testosterone decreased with age to a similar extent across all groups.

CONCLUSIONS

These results suggest that changes in BMI during young adulthood modulate age-related changes in SHBG and total testosterone, but not bioavailable testosterone.

Testosterone Levels Among Men with Spinal Cord Injury Admitted to Inpatient Rehabilitation

OBJECTIVE

Although previous research has shown an association between spinal cord injury (SCI) and testosterone production, these studies have yielded inconsistent results. The present study documented the prevalence of low testosterone among men with SCI.

DESIGN

Participants were 92 men with SCI participating in inpatient rehabilitation. Data included total serum testosterone level, demographic and injury information, neurologic level and degree of incomplete function, American Spinal Injury Association Impairment Scale grade, and additional laboratory values, including prealbumin, albumin, hematocrit, and aspartate aminotransferase.

RESULTS

The median testosterone level for men who sustained injuries <4 mos earlier was 160 ng/dl. Testosterone categories were significantly associated with age, time since injury, hematocrit, albumin level, and aspartate aminotransferase in the univariate analyses. Age, time since injury, and hematocrit levels were significant predictors of low testosterone in the multivariate analysis.

CONCLUSION

The prevalence of low testosterone among men with acute SCI seems to be high. The results suggest the need for routine screening for low testosterone among men with SCI and consideration given to testosterone replacement therapy. Future research is needed to investigate the etiology, pathogenesis, and potential avenues for treatment of low testosterone among men with SCI.

[LOH (late-onset hypogonadism) or the "aging male"]

Due to lacking evidence of the data about testosterone deficiency of the aging male or LOH (late-onset hypogonadism), this subject is still a challenge for urologists, endocrinologists, and dermatologists or andrologists. This challenge faces basic research as well as clinical investigations. We have to accept responsibility for solving this challenge to better understand and better treat our patients beyond the scope of current guidelines.

Prevalence of hypogonadism in males aged at least 45 years: the HIM study

The Hypogonadism in Males study estimated the prevalence of hypogonadism [total testosterone (TT) < 300 ng/dl] in men aged > or = 45 years visiting primary care practices in the United States. A blood sample was obtained between 8 am and noon and assayed for TT, free testosterone (FT) and bioavailable testosterone (BAT). Common symptoms of hypogonadism, comorbid conditions, demographics and reason for visit were recorded. Of 2162 patients, 836 were hypogonadal, with 80 receiving testosterone. Crude prevalence rate of hypogonadism was 38.7%. Similar trends were observed for FT and BAT. Among men not receiving testosterone, 756 (36.3%) were hypogonadal; odds ratios for having hypogonadism were significantly higher in men with hypertension (1.84), hyperlipidaemia (1.47), diabetes (2.09), obesity (2.38), prostate disease (1.29) and asthma or chronic obstructive pulmonary disease (1.40) than in men without these conditions. The prevalence of hypogonadism was 38.7% in men aged > or = 45 years presenting to primary care offices.

Management of the cardinal features of andropause

There are several problems facing aging men, especially sexual dysfunction, hypogonadism, and psychologic changes. This constellation of changes is sometimes referred to as "manopause" or "andropause." Unlike the dramatic changes in the hormonal milieu occurring during menopause in women, the age-related changes in reproductive hormones of men are subtle and occur gradually throughout the years of mature life. It has been estimated that circulating testosterone (T) declines longitudinally from age 19 at an average rate of 1% per year. The free or dialyzable fraction of serum T and the bioavailable (the sum of free fraction and loosely bound to albumin fraction) T decline more rapidly with age. Although the essential role of androgens in reproductive tissue development and emergence of secondary sex characteristics is well known, their role in adult sexual function seems to be primarily facultative. The effect of T on the central nervous system extends beyond sexual behavior. T has been shown to alter mood, memory, ability to concentrate, and the overall sense of vigor and well being that may interact with a host of other psychologic changes associated with aging. Disordered erectile function is not generally an endocrine problem but rather vascular, neurologic, and psychogenic in origin. It also may be the first sign of systemic vascular disease. The clinical management of andropause requires an individualized approach. In some men, the main problem may be psychologic, whereas in others, hypogonadism may play an important role. Many with erectile failure, suffer silently regardless of its etiology. In this review, we suggest some practical guidelines for the management of these conditions.

Association among hypogonadism, quality of life and erectile dysfunction in middle-aged and aged male in Taiwan

The association between hypogonadism, quality of life (QoL), and erectile dysfunction (ED) among the middle-aged and aged male in Taiwan is evaluated. A total of 680 study subjects aged >or=40 years old were recruited from Northern (n=276), Middle (n=238), and Southern (n=202) Taiwan, respectively. ED was diagnosed by score of International Index of Erectile Function (IIEF-5). Taiwan version questionnaire for QoL includes domain 1 (physical domain), domain 2 (psychological domain), domain 3 (social relationship domain), and domain 4 (environmental domain) was used to measure QoL. Blood hormones, including FSH, LH, Prolactin, SHBG, total testosterone (TT), calculated free testosterone (cFT), and bioavailable testosterone (Bio-T), were determined. Logistic regression analysis was used to estimate crude and multivariate-adjusted odds ratio of risk factors and its 95% confidence interval. A significantly inverse association between concentration of serum cFT and Bio-T, and severity of ED was observed. Scores of QoL of Domain 1-4 were significantly decreased with the increament of severity of ED. Significant correlations were found between IIEF scores and four domains of QoL, respectively. After adjustment for age, cFT and Bio-T, study subjects with ED (IIEF<or=21) would have significantly high risk of low level of QoL in four domains. In conclusion, a significant association between low levels of serum calculated cFT, Bio-T, and severity of ED was found. In addition, abnormal erectile function significantly associated with low level of QoL in four domains.

REVIEWS: Are Androgens Critical for Penile Erections in Humans? Examining the Clinical and Preclinical Evidence

Androgens are deemed critical for penile-tissue development, growth, and maintenance of erectile function, however, their role in erection, especially in humans, remains controversial. In this review, we summarize information from clinical and animal model studies to provide a comprehensive and rational argument for the role of androgens, or lack thereof, on penile erection ability in humans. The goal of this review is to present the clinical and preclinical evidence available in the literature with regard to testosterone and erectile physiology and engage the reader in this discussion. Ultimately, each reader will have to form his or her own conclusions based on the existing evidence. In humans, androgen-deficiency manifestations are noted in clinical situations such as: (i) inadequate development of the penis; and (ii) loss of erectile function in prostate cancer and benign prostatic hyperplasia patients managed with medical or surgical castration or antiandrogen therapy. Androgen treatment causes: (i) improvement in sexual function in hypogonadal patients treated with androgen supplementation; (ii) improvement in nocturnal penile tumescence in hypogonadal patients treated with androgens; (iii) improvement in erectile function with androgen supplementation in patients who did not respond to phosphodiesterase type 5 inhibitor therapy initially; and (iv) improvement in the well-being, mood, energy, and sexual function in aging men who have testosterone deficiency treated with androgen therapy. In contrast to animals, especially rodents in which the adrenal cortex does not synthesize androgens, the human adrenal is a source of peripherally circulating androgen precursors, thus, complete androgen insufficiency may not be observed in men at a younger age. Furthermore, in light of the concept that a threshold of androgen levels exists in animals and humans below which sexual function is diminished, further contributes to the complexity of understanding androgens role in erections, especially in humans. Nevertheless, based on the preclinical and clinical data available in the literature, to date, we infer that androgens play a critical role in maintaining erectile physiology in humans.

Predictors of South African male testosterone levels: the THUSA study

The process of urbanization occurring in many developing countries may have consequences for reproductive endocrine function. Here, we test predictions concerning variation in South African male testosterone levels among subgroups across an urbanization gradient representing differences in both geography and socioeconomic status. Subjects included 364 males aged between 20 and 82 comprising a cross-sectional study conducted between 1996 and 1998. Testosterone levels were measured from serum samples obtained between 08:00 and 11:00. In ANCOVA analysis, male testosterone levels differed significantly along this rural-to-urban gradient, with members of the most urban group having higher testosterone levels than groups of farmers and inhabitants of informal housing areas adjacent to towns. Testosterone levels declined with age and were negatively related to body mass index (BMI). Testosterone levels did not differ according to HIV status. Further exploratory ANCOVA analyses revealed that physical activity levels, depression, affect, and hostility were not significantly associated with variation in testosterone levels. These data help document causes of variation in male testosterone levels in a context of urbanization and may have implications for clinical outcomes such as the development of a male hormonal contraceptive or prostate cancer.

Androgens, aging, and Alzheimer's disease

Testosterone depletion is a normal consequence of aging in men that is associated with senescent effects in androgen- responsive tissues. We discuss new evidence that one consequence of testosterone depletion in men is an increased risk for the development of Alzheimer's disease (AD). Furthermore, we discuss two candidate mechanisms by which testosterone may affect AD pathogenesis. First, testosterone has been identified as an endogenous regulator of beta-amyloid, a protein that abnormally accumulates in AD brain and is implicated as a causal factor in the disease. Second, findings from several different paradigms indicate that testosterone has both neurotrophic and neuroprotective functions. These new findings support the clinical evaluation of androgen-based therapies for the prevention and treatment of AD.

Soy isoflavones and bone health: a double-edged sword?

Numerous publications and research studies on isoflavones have prompted a nationwide increase in the consumption of soy-based foods and supplements in the United States. Isoflavones are natural endocrine active compounds generally considered to promote health and prevent or slow the onset of certain chronic diseases such as osteoporosis. The beneficial effects of soy isoflavones on bone may, however, be life-stage specific and dependent on the estrogen receptor number and endogenous hormone milieu. Perimenopausal and early menopausal women may therefore be more receptive to the therapeutic effects of isoflavones on bone loss prior to the diminution of estrogen receptors that occurs in the postmenopausal years, whereas laboratory studies in developmental age range animals have demonstrated the potential for adverse effects following exposure to high levels of soy isoflavones. Clinical studies in developing humans that either support or refute findings in animal studies are lacking. The effects of chronic consumption of high levels of soy isoflavones at each life stage to assess risk-benefit ratios should be a high priority of research.

Gonadotropins: potential targets for preventive and therapeutic interventions in Alzheimer’s disease

Increased prevalence of Alzheimer’s disease (AD) in women has led to an interest in the role of hormonal changes in the neurodegenerative process. In particular, research has been directed towards investigating the effect of changes in sex hormone levels following reproductive senescence. Clinical trials of hormone-replacement therapy for the prevention of AD are proving contentious, and considerably more research is necessary before the benefit of the hormone replacement strategy can be ascertained. However, evidence is now emerging to support the notion that increased gonadotropin levels may confer an increased risk of AD. Gonadotropins have been implicated in the metabolism of β-amyloid, a key protein that is central to the pathogenesis of AD. Gonadotropin reduction represents a promising new target for therapeutic intervention in AD and, potentially, dementia in general. In this review, the authors discuss the therapeutic and preventive potential of gonadotropin-reducing agents in the management of AD.

Serum testosterone levels using the radioimmunoassay method in healthy Japanese male volunteers

Aim:  The objective of the present study was to measure serum free and total testosterone values using the radioimmunoassay (RIA) method in healthy Japanese male volunteers with no current diseases. Methods:  Two hundred and fifty-one healthy men who had no medical illness and received no current medical treatment were selected from 405 male volunteers. Free and total testosterone were measured in blood samples using the RIA method. Results:  Free but not total testosterone significantly decreased with age. Mean free testosterone values from morning blood samples for each age decade from the 20s to the 70s were 17.0, 14.6, 12.5, 10.6, 8.9 and 8.5 pg/mL, respectively. Mean total testosterone values from morning blood samples for each age decade from the 20s to the 70s were 4.7, 4.2, 4.4, 4.2, 4.2, 4.0 and 4.0 ng/mL, respectively. The rates of healthy volunteers that fell within the standard reference ranges for free and total testosterone were 97% and 97%, respectively. However, 19% of the total testosterone values were considered to indicate hypogonadism according to the International Society for the Study of the Aging Male (ISSAM) criteria (<3.17 ng/mL). Conclusions:  Our data corresponded to the standard reference ranges of Japanese men but not the ISSAM criteria. It may be more appropriate to establish a standard reference range for serum testosterone for individual countries. (Reprod Med Biol 2006; 5: 37-41).

Low sex hormone-binding globulin, total testosterone, and symptomatic androgen deficiency are associated with development of the metabolic syndrome in nonobese men

BACKGROUND

The metabolic syndrome (MetS), characterized by central obesity, lipid and insulin dysregulation, and hypertension, is a precursor state for cardiovascular disease. The purpose of this analysis was to determine whether low serum sex hormone levels or clinical androgen deficiency (AD) predict the development of MetS.

METHODS

Data were obtained from the Massachusetts Male Aging Study, a population-based prospective cohort of 1709 men observed at three time points (T1, 1987-1989; T2, 1995-1997; T3, 2002-2004). MetS was defined using a modification of the ATP III guidelines. Clinical AD was defined using a combination of testosterone levels and clinical signs and symptoms. The association between MetS and sex hormone levels or clinical AD was assessed using relative risks (RR), and 95% confidence intervals (95% CI) were estimated using Poisson regression models.

RESULTS

Analysis was conducted in 950 men without MetS at T1. Lower levels of total testosterone and SHBG were predictive of MetS, particularly among men with a body mass index (BMI) below 25 kg/m2 with adjusted RRs for a decrease in 1 sd of 1.41 (95% CI, 1.06-1.87) and 1.65 (95% CI, 1.12-2.42). Results were similar for the AD and MetS association, with RRs of 2.51 (95% CI, 1.12-5.65) among men with a BMI less than 25 compared with an RR of 1.22 (95% CI, 0.66-2.24) in men with a BMI of 25 or greater.

CONCLUSIONS

Low serum SHBG, low total testosterone, and clinical AD are associated with increased risk of developing MetS over time, particularly in nonoverweight, middle-aged men (BMI, <25). Together, these results suggest that low SHBG and/or AD may provide early warning signs for cardiovascular risk and an opportunity for early intervention in nonobese men.

Normative hypogonadism and depression: does ‘andropause’ exist?

The progressive decline in testosterone level has been demonstrated in both cross-sectional and longitudinal studies, and overall at least 25% of men over the age of 70 years meet laboratory criteria for hypogonadism (i.e., testosterone deficiency). Such age-associated HPG hypofunctioning, which has been termed 'andropause', is thought to be responsible for a variety of symptoms experienced by elderly men, including sexual dysfunction and depression. Although, it has been difficult to establish correlations between 'andropausal' symptoms and plasma testosterone levels, there is some evidence that testosterone replacement leads to improvement in muscle strength, bone mineral density, and erectile dysfunction. There is little evidence of a link between HPG-axis dysfunction and depressive illness, and exogenous androgens have not been consistently shown to be antidepressant. This article reviews the relationship between androgens and depression in aging men.

Endogenous sex steroids, weight change and rates of hip bone loss in older men: the MrOS study

INTRODUCTION

Lower levels of endogenous sex steroids or declines in these hormones may contribute to the increased rates of bone loss observed in older adults experiencing weight loss. We hypothesized that among older men with weight loss, higher rates of bone loss at the hip would be observed in men with lower baseline bioavailable sex steroids or those with greater declines in these hormones.

METHODS

To test this hypothesis, body weight, hip bone mineral density (BMD) using dual energy x-ray absorptiometry and endogenous sex steroids in paired serum samples by sensitive immunoassays were measured at a baseline and at a second examination that was held an average of 1.8 years later in 1267 older men enrolled in the Osteoporotic Fractures in Men (MrOS) study.

RESULTS

Men experiencing weight loss had higher rates of hip bone loss than those with stable weight or weight gain within each quartile of baseline sex steroid level [p values for test of trend across weight change categories <0.010 within each quartile of bioavailable estradiol and testosterone and <0.060 within each quartile of sex hormone-binding globulin (SHBG)]. Results were similar when a change in sex steroids was substituted for baseline sex steroids in the analyses. Among men with weight loss, the rate of decline in total hip BMD showed a stepwise increase in magnitude with decreasing baseline bioavailable estradiol (p value for trend <0.040), with increasing baseline SHBG (p value for trend<0.030) and with greater decreases in bioavailable testosterone from baseline (p value for trend <0.001).

CONCLUSIONS

These findings support the hypothesis that the impact of weight loss in older men on rates of hip bone loss may be increased by the presence of a sex steroid insufficiency.

Sexual dysfunction in the elderly: age or disease?

Sexuality is an important component of emotional and physical intimacy that men and women experience through their lives. Male erectile dysfunction (ED) and female sexual dysfunction increase with age. About a third of the elderly population has at least one complaint with their sexual function. However, about 60% of the elderly population expresses their interest for maintaining sexual activity. Although aging and functional decline may affect sexual function, when sexual dysfunction is diagnosed, physicians should rule out disease or side effects of medications. Common disorders related to sexual dysfunction include cardiovascular disease, diabetes, lower urinary tract symptoms and depression. Early control of cardiovascular risk factors may improve endothelial function and reduce the occurrence of ED. Treating those disorders or modifying lifestyle-related risk factors (eg obesity) may help prevent sexual dysfunction in the elderly. Sexuality is important for older adults, but interest in discussing aspects of sexual life is variable. Physicians should give their patient's opportunity to voice their concerns with sexual function and offer them alternatives for evaluation and treatment.

Determinants of bone mineral density in Chinese men

Osteoporotic fractures are increasing among Asian populations in both genders, but the risk factors for low bone mineral density (BMD) in Asian men is unclear. To determine the hormonal and lifestyle risk factors for low BMD in Asian men, we studied 407 community-dwelling southern Chinese men aged 50 years and above. Medical history and lifestyle habits were obtained with a structured questionnaire. Dietary calcium and phytoestrogen intake were assessed by a semi-quantitative questionnaire. BMD at the spine and hip were measured by dual-energy X-ray absorptiometry (DXA). Fasting blood was analyzed for 25(OH)D, parathyroid hormone (PTH), total and bioavailable estradiol (bio-E) and testosterone (bio-T). The mean age of the cohort was 68.42+/-10.4 (50-96) years. In the linear regression model, weight, age, body mass index (BMI), bio-E, PTH, cigarette smoking and weight-bearing exercise were significant determinants of total hip BMD. Together they explained 55% of the total variance of hip BMD, with body weight being the most important determining factor. With age and weight adjustment, height, bio-T and flavonoid intake were identified as additional determinants of total hip BMD. Strategies to prevent bone loss and osteoporosis in Asian men should include lifestyle modification and maintenance of hormonal sufficiency.

Effect of aromatase inhibition on bone metabolism in elderly hypogonadal men

Both estrogens and androgens play important roles in skeletal development and maintenance in men. The relative importance of estrogens and androgens in male bone metabolism, however, remains undefined. Anastrozole is an oral aromatase inhibitor that decreases estrogen production and increases androgen production in men. Currently, anastrozole is being investigated as a potential agent for the treatment of hypogonadism in aging men. Because anastrozole lowers estrogen levels and raises androgen levels, its effect on bone metabolism is difficult to predict. To assess the effects of anastrozole on bone turnover, we randomized 37 elderly (ages 62-74) mildly hypogonadal men (serum testosterone <350 ng/dl) to receive either anastrozole 1 mg daily (n=12), anastrozole 1 mg twice weekly (n=11), or daily placebo (n=14) for 12 weeks. Serum gonadal steroid levels, serum and urine biochemical markers of bone turnover, serum osteoprotegerin, and total body bone mineral density were measured at baseline and week 12. Mean serum levels of total and bioavailable testosterone increased substantially in both treated groups. Specifically, mean +/- SD bioavailable testosterone levels increased from 99+/-31 ng/dl to 207+/-65 ng/dl in the group receiving 1 mg of anastrozole daily and from 115+/-37 ng/dl to 178+/-55 ng/dl in the subjects receiving 1 mg of anastrozole twice weekly ( p <0.001 vs placebo for both groups). Serum estradiol levels decreased modestly in both treated groups (from 26+/-8 pg/ml to 17+/-6 pg/ml in the daily treatment group and from 27+/-8 pg/ml to 17+/-5 pg/ml in the twice-weekly treatment group, p <0.001 vs placebo for both groups). Despite these hormonal changes, no increases in biochemical markers of bone resorption were observed. Specifically, mean serum N-telopeptide and urinary deoxypyridinoline concentrations remained stable in both treated groups over the 12-week treatment period. Similarly, serum biochemical markers of bone formation (osteocalcin and amino-terminal propeptide of type 1 collagen), serum osteoprotegerin, and total body bone mineral density did not change. These data demonstrate that although short-term administration of anastrozole decreases serum estradiol levels in elderly men with mild hypogonadism, this intervention does not adversely affect bone metabolism over a 12-week period. This lack of an effect may be due to the concomitant increase in testosterone production, the relative modest effect on estradiol production, or a combination of both factors. These results suggest that anastrozole therapy is unlikely to have an adverse effect on bone metabolism when taken over extended periods and may prove to be a valuable method of normalizing testosterone production in older men.

Correlations of androgen deficiency with clinical symptoms in Taiwanese males

The purpose of this study was to elucidate correlations between different biochemical measurements of androgen deficiency and clinical symptoms in male residents of Taiwan. An investigation of the serum biochemical markers for androgen deficiency in 650 males, including total testosterone, calculated free testosterone, and bioavailable testosterone, was conducted. Measurements of clinical symptoms were obtained using a questionnaire of the androgen deficiency in the aging male (ADAM) by St Louis University (SLQ). Correlations among the biochemical markers, correlations of the biochemical markers and age, and relationships between the biochemical markers and the SLQ were evaluated. The sensitivity and specificity of the SLQ were determined. Bioavailable and calculated free testosterone correlated better with age than did total testosterone. Eighty percent of the men had a positive SLQ, and 20% had a negative SLQ. The percentage of positive SLQ results increased with age. No statistically significant difference was noted between the biochemical markers of bioavailable and calculated free testosterone levels and the SLQ status except for men aged over 70 years. The SLQ in this study showed an acceptable sensitivity of about 80%, but the specificity was poor (about 20%). In conclusion, bioavailable testosterone and calculated free testosterone were more-closely correlated with age and may be better biochemical markers for androgen deficiency. SLQ might not be a suitable single measurement for androgen deficiency and should be used together with biochemical markers.

Testosterone replacement therapy and the risk of prostate cancer. Is there a link?

Substantial evidence supports the value of testosterone replacement therapy (TRT) in improving quality of life in men with proven aging male syndrome (AMS). Benefits of TRT include improved bone mineral density, reduced fracture risk, increased muscle mass, and improved mood, sense of well being, and libido, among others. There is currently a heated debate about the theoretical association between TRT and the initiation, progression, and aggressiveness of prostate cancer; however, this link has not been uniformly studied, and any results have been contradictory and nonconclusive. Although no clear evidence links TRT to prostate cancer, the possibility of increasing the risk of a clinical manifestation of a latent pre-existing malignancy can influence the decision about TRT use. Current recommendations are to exclude prostate cancer before initiating TRT in men over age 40 and to closely monitor men in the first year of testosterone replacement, followed by observation in subsequent years.

Testosterone supplementation in aging men and women: possible impact on cardiovascular-renal disease

Treatment of aging men and women with testosterone supplements is increasing. The supplements are given to postmenopausal women mainly to improve their libido and to aging men to improve muscle mass and bone strength, to improve libido and quality of life, to prevent and treat osteoporosis, and, with the phosphodiesterase-5 inhibitors, such as sildenafil, to treat erectile dysfunction. The increased use of testosterone supplements in aging individuals has occurred despite the fact that there have been no rigorous clinical trials examining the effects of chronic testosterone on the cardiovascular-renal disease risk. Studies in humans and animals have suggested that androgens can increase blood pressure and compromise renal function. Androgens have been shown to increase tubular sodium and water reabsorption and activate various vasoconstrictor systems in the kidney, such as the renin-angiotensin system and endothelin. There is also evidence that androgens may increase oxidative stress. Furthermore, the kidney contains the enzymes necessary to produce androgens de novo. This review presents an overview of the data from human and animal studies in which the role of androgens in promoting renal and cardiovascular diseases has been investigated.

Reproductive hormone reference intervals for healthy fertile young men: evaluation of automated platform assays

CONTEXT

Management of male infertility and/or androgen deficiency requires accurate hormonal measurements with valid reference intervals.

OBJECTIVE

The objective of this study was to develop a valid reference panel of blood samples from healthy eugonadal young men with verified normal reproductive function and to use this panel to evaluate the performance of seven fully automated, commercial multiplex immunoassay platforms used to measure serum total testosterone (T), LH, and FSH.

DESIGN

This was an observational study of consistency among seven different automated immunoassays for each of total T, LH, and FSH. Each method was implemented in two laboratories, with each repeating the analysis of the full reference panel samples twice. Serum T concentrations were also measured by gas chromatography/mass spectrometry (GC/MS), and serum inhibin B levels were determined by an ELISA.

SETTING

The study was performed at commercial, high-volume, clinical pathology laboratories.

PARTICIPANTS

From 147 men screened, sera from 124 healthy, reproductively normal men (age, 21-35 yr) with normal sperm output were used as a reference panel. All laboratories selected for elite performance in the national immunoassay quality assurance program agreed to participate.

MAIN OUTCOME MEASURE(S)

For each of the 868 assays, descriptive statistics were calculated in the natural and log-transformed scales and were analyzed by nested, repeated measures ANOVA after log transformation. Reference intervals, defined as 95% confidence limits, were calculated using arithmetic (natural scale), geometric (log scale) and nonparametric methods.

RESULTS

Descriptive statistics and reference intervals for serum T, LH, and FSH differed widely and significantly between methods, but variation between laboratories for the same assay was negligible. All T methods showed significant differences in regression slope and intercept in deviance plots as well as in estimated reference ranges compared with the independent GC/MS reference method. Although similar between-method differences existed for gonadotropin assays, the smaller quantitative discrepancies allowed assignment of consensus reference intervals for serum FSH (1.3-8.4 IU/liter) and LH (1.6-8.0 IU/liter), although these differed from manufacturers' currently quoted expected values.

CONCLUSIONS

Using a reference panel of sera from healthy eugonadal young men with verified normal reproductive function, major differences exist between commercial T immunoassays as well as divergence from the GC/MS standard. This impairs their clinical diagnostic utility and requires substantial improvements in automated T immunoassay technologies or a switch to GC/MS methods. Gonadotropin assays showed less variability, but current high-throughput immunoassays remain suboptimal to confirm accurate diagnosis of azoospermia or androgen deficiency.

Testosterone and Sleep‐Related Erections: An Overview*

Sleep-related erections have been reported to occur from the intrauterine life to senescence. It has been speculated that the main function of nocturnal erections is to provide adequate engorgement of the corpora cavernosa, which then leads to increased tissue oxygenation. This is in turn to prevent cavernous fibrosis, the histopathological basis for corporeal venoocclusive dysfunction, which probably is the most common cause of organic erectile dysfunction. It has been suggested that sleep-related erections are triggered by the release of nitric oxide by the nitrergic nerve fibers within the cavernous nerves. Androgens regulate this mechanism as well as some other non-nitrergic processes within the corpora cavernosa and within the central nervous system. By contrast, the erectile response to tactile or visual erotic stimuli in wakefulness predominantly involves an androgen-independent system, although it may, at least to a certain degree, also be influenced by androgen-sensitive mechanisms. No doubt, androgens are key players in the physiology of nocturnal erections, and the availability of new, user-friendly testosterone preparations such as transdermal gel and intramuscularly administered testosterone undecanoate stimulates further investigations on this field. The prospect that the quality of sleep may also be improved by an androgen therapy administered to improve sleep-related erections in hypogonadal men needs further basic research and appropriate clinical studies.

Molecular aspects of declining sperm motility in older men

OBJECTIVE

To investigate the molecular mechanism for declining sperm motility in older men.

DESIGN

Retrospective and prospective study.

SETTING

University-based andrology unit.

PATIENT(S)

Semen was collected from 2,111 patients and sperm donors.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Age, sperm concentration, ejaculate volume, sperm motility (including velocity average path, velocity straight line, velocity curvilinear, linearity, and lateral head displacement), normal sperm morphology, percentage of abnormally blue-stained flagella, and total and free T, FSH, and LH concentrations were analyzed. In addition, the zinc concentration in the seminal fluid, flagella, and the whole spermatozoa was measured by means of atomic absorption spectrometry.

RESULT(S)

Patient age correlated negatively with T concentration and sperm motility, including velocity, but positively with the percentage of abnormally stained flagella and the flagellar zinc. Whereas the percentage of abnormally stained flagella correlated negatively with motility and sperm velocity, there was a positive relationship with the flagellar zinc content. Flagellar zinc content was negatively correlated with motility. Testosterone showed a positive relationship with motility and sperm concentration.

CONCLUSION(S)

Because the epididymis is functionally T-dependent, our data suggest that the removal of zinc from the outer dense fibers during epididymal sperm maturation is affected in aging men, which in turn will result in decreased sperm motility.

The decline of androgen levels in elderly men and its clinical and therapeutic implications

Aging in men is accompanied by a progressive, but individually variable decline of serum testosterone production, more than 20% of healthy men over 60 yr of age presenting with serum levels below the range for young men. Albeit the clinical picture of aging in men is reminiscent of that of hypogonadism in young men and decreased testosterone production appears to play a role in part of these clinical changes in at least some elderly men, the clinical relevancy of the age-related decline in sex steroid levels in men has not been unequivocally established. In fact, minimal androgen requirements for elderly men remain poorly defined and are likely to vary between individuals. Consequently, borderline androgen deficiency cannot be reliably diagnosed in the elderly, and strict differentiation between "substitutive" and "pharmacological" androgen administration is not possible. To date, only a few hundred elderly men have received androgen therapy in the setting of a randomized, controlled study, and many of these men were not androgen deficient. Most consistent effects of treatment have been on body composition, but to date there is no evidence-based documentation of clinical benefits of androgen administration to elderly men with normal or moderately low serum testosterone in terms of diminished morbidity or of improved survival or quality of life. Until the long-term risk-benefit ratio for androgen administration to elderly is established in adequately powered trials of longer duration, androgen administration to elderly men should be reserved for the minority of elderly men who have both clear clinical symptoms of hypogonadism and frankly low serum testosterone levels.

Therapie des „Aging male“

Serum testosterone levels decline in men with increasing age. Late-onset hypogonadism with its characteristic symptoms can occur in men as they age. Typical symptoms of late-onset hypogonadism are decreased libido and sexual function, osteoporosis, altered distribution of body fat, overall reduction in physical strength, and alterations in general mood. Late-onset hypogonadism can be treated with testosterone, and different forms of testosterone have become available for this indication. The aim of testosterone replacement therapy is to produce serum testosterone levels within the physiological range avoiding levels above and below this range. Although hormone replacement therapy has become accepted in aging males, careful consideration of the indications and therapy monitoring are still required since there are major concerns about the long-term outcome of this therapy and particularly its effects on the prostate gland.

No major month to month variation in free testosterone levels in aging males. Minor impact on the biological diagnosis of 'andropause'

BACKGROUND

The measurement of bioavailable testosterone (BT) or free testosterone (FT) levels is currently considered the gold standard for the diagnosis of androgen deficiency in elderly men. While the impact of age on circulating testosterone levels (total, bioavailable and free) has been strongly documented, the existence of seasonal variations in testosterone levels remains debated.

OBJECTIVE

We investigated whether seasonal variations in serum calculated free testosterone (cFT) levels may translate into variations in the prevalence of low testosterone levels. Diagnosis was on the basis of biochemical determinations and was cross-checked with the prevalence of clinical signs and symptoms of 'andropause', as assessed by the Androgen Deficiency in Aging Males (ADAM) questionnaire.

METHODS

The study recruited 5028 men aged 50 years and over from September 2000 to January 2003. Their serum FT levels were assessed and they completed the French ADAM test. Men were considered eugonadal when cFT was > or =70 ng/l. The ADAM test was scored as described originally. The prevalence of 'andropause', diagnosed by the two methods, was compared throughout the year, on a month by month basis.

RESULTS

The percentage of subjects with cFT levels below 70 ng/l increased significantly with age (P<0.001). Serum cFT levels (mean [SD]) varied significantly with the month of sampling (P<0.0001), the highest (88.1 [30.2] ng/l) and lowest (76.9 [28.0] ng/l) mean values occurring in April and in October, respectively. Conversely, the prevalence of testosterone deficiency (cFT<70 ng/l) reached a peak in October (45.7%) and a nadir in April (29.7%). Although the prevalence of 'andropause', based on the ADAM questionnaire, increased significantly with age (P<0.0001), no influence of the month of the year was noticed.

CONCLUSIONS

Our results confirm a progressive age-related decline in FT levels. The monthly variations in serum FT values, observed throughout the year, do not show a major seasonal rhythm in elderly community-dwelling males, since the magnitude of the variations (<15%) remains marginal. This slight variation may, however, have an impact on the number of elderly men diagnosed with Partial Androgen Deficiency in Aging Males (PADAM).

Relationship between testosterone levels, insulin sensitivity, and mitochondrial function in men

OBJECTIVE

The goal of this study was to examine the relationship between serum testosterone levels and insulin sensitivity and mitochondrial function in men.

RESEARCH DESIGN AND METHODS

A total of 60 men (mean age 60.5 +/- 1.2 years) had a detailed hormonal and metabolic evaluation. Insulin sensitivity was measured using a hyperinsulinemic-euglycemic clamp. Mitochondrial function was assessed by measuring maximal aerobic capacity (V(O2max)) and expression of oxidative phosphorylation genes in skeletal muscle.

RESULTS

A total of 45% of subjects had normal glucose tolerance, 20% had impaired glucose tolerance, and 35% had type 2 diabetes. Testosterone levels were positively correlated with insulin sensitivity (r = 0.4, P < 0.005). Subjects with hypogonadal testosterone levels (n = 10) had a BMI >25 kg/m(2) and a threefold higher prevalence of the metabolic syndrome than their eugonadal counterparts (n = 50); this relationship held true after adjusting for age and sex hormone-binding globulin but not BMI. Testosterone levels also correlated with V(O2max) (r = 0.43, P < 0.05) and oxidative phosphorylation gene expression (r = 0.57, P < 0.0001).

CONCLUSIONS

These data indicate that low serum testosterone levels are associated with an adverse metabolic profile and suggest a novel unifying mechanism for the previously independent observations that low testosterone levels and impaired mitochondrial function promote insulin resistance in men.

Age-specific changes in the regulation of LH-dependent testosterone secretion: assessing responsiveness to varying endogenous gonadotropin output in normal men

Pulsatile and thus total testosterone (Te) secretion declines in older men, albeit for unknown reasons. Analytical models forecast that aging may reduce the capability of endogenous luteinizing hormone (LH) pulses to stimulate Leydig cell steroidogenesis. This notion has been difficult to test experimentally. The present study used graded doses of a selective gonadotropin releasing hormone (GnRH)-receptor antagonist to yield four distinct strata of pulsatile LH release in each of 18 healthy men ages 23-72 yr. Deconvolution analysis was applied to frequently sampled LH and Te concentration time series to quantitate pulsatile Te secretion over a 16-h interval. Log-linear regression was used to relate pulsatile LH secretion to attendant pulsatile Te secretion (LH-Te drive) across the four stepwise interventions in each subject. Linear regression of the 18 individual estimates of LH-Te feedforward dose-response slopes on age disclosed a strongly negative relationship (r = -0.721, P < 0.001). Accordingly, the present data support the thesis that aging in healthy men attenuates amplitude-dependent LH drive of burst-like Te secretion. The experimental strategy of graded suppression of neuroglandular outflow may have utility in estimating dose-response adaptations in other endocrine systems.

Graded inhibition of pulsatile luteinizing hormone secretion by a selective gonadotropin-releasing hormone (GnRH)-receptor antagonist in healthy men: evidence that age attenuates hypothalamic GnRH outflow

Healthy older men manifest concomitant hypoandrogenemia and attenuation of LH pulse size. Because exogenous GnRH remains effective, a plausible intuition is that aging reduces hypothalamic GnRH secretion, thus mediating relative hypogonadotropic hypogonadism. To assess the impact of age on central GnRH outflow indirectly, we quantitated graded suppression of pulsatile LH secretion by saline and escalating doses of a potent and selective GnRH-receptor antagonist, ganirelix, in 18 healthy men ages 23-72 yr. The rationale is that ganirelix should reduce the amplitude of LH pulses in proportion to both drug concentration and endogenous GnRH feedforward. To this end, blood was sampled every 10 min for 2 h before and 16 h after sc administration of saline or ganirelix and for 3 additional hours after iv injection of a fixed dose of GnRH (100 ng/kg); concentrations of LH and ganirelix were measured by immunochemiluminometry and RIA, respectively; and pulsatile LH secretion was quantitated by a deconvolution procedure. Log-linear regression analysis was used to estimate the sensitivity of pulsatile LH secretion to inhibition by a unit increase in serum ganirelix concentrations in each subject. Statistical analyses revealed that increasing age markedly attenuated the capability of ganirelix to decrease LH pulse size (viz., r = -0.648; P = 0.004). In contrast, age did not modify the competitive interaction between injected GnRH and ganirelix. These joint outcomes support the clinical hypothesis that age diminishes hypothalamic GnRH outflow without impairing GnRH action in healthy men.

Hypogonadism in hereditary hemochromatosis

Hypogonadism, usually hypogonadotropic in origin, is the most common nondiabetic endocrinopathy in hereditary hemochromatosis (HH). Early studies, usually evaluating small numbers of patients with advanced HH, report prevalence rates of 10-100%. The clinical presentation of HH has changed in recent years as a result of increased awareness and screening. We assessed the prevalence of hypogonadism in a large group of patients with HH diagnosed in a single center over the past 20 yr, the period of follow-up spanning the time before and after widespread screening was introduced and the HFE gene was recognized. Abnormally low plasma testosterone levels, with low LH and FSH levels, were found in nine of 141 (6.4%) male patients tested. Eight of nine (89%) had associated hepatic cirrhosis; three of nine (33%) had diabetes. Inappropriately low LH and FSH levels were found in two of 38 females (5.2%) in whom the pituitary-gonadal axis could be assessed. This is the largest detailed study of hypogonadism reported in HH. The lower prevalence of hypogonadism compared with other reported series reflects the earlier diagnosis of HH in an unselected group of patients attending a single center. Patients with lesser degrees of hepatic siderosis at diagnosis are unlikely to develop hypogonadism.

Aging and pathogenesis of erectile dysfunction

The prevalence and the severity of erectile dysfunction (ED) increase with advancing age; different pathogenetic factors could contribute to age-related ED. We studied organic, relational and intrapsychic components of ED as a function of patients' age in a consecutive series of 977 patients with ED, using the specifically designed structured interview SIEDY. A complete physical examination and a series of biochemical, hormonal, psychometric and penile vascular tests were also performed. Relational factors seems to be more relevant in patients aged over 60 y, while intrapsychic disturbances play a major role in younger subjects. Organic factors are the most important determinant of ED in all age groups, but their contribution is more important in older patients. In fact, basal and dynamic peak cavernosal velocity at Doppler ultrasound penile examination was reduced in older patients. Among hormonal factors, the body mass index-dependent reduction of testosterone in older patients does not seem to play a crucial role in the pathogenesis of ED. No significant correlation was observed between testosterone level and the severity of ED, although patients reporting hypoactive sexual desire showed significantly lower testosterone levels when compared with the rest of the sample. A better understanding of the relative contribution of age-related pathogenetic factors of ED could be of help in the design of appropriate therapeutic approaches.

Andropause: Is Androgen Replacement Therapy Indicated for the Aging Male?

The number of men in the United States > or =65 years of age is projected to increase from 14,452,000 in 2000 to 31,343,000 in 2030. Approximately 30% of men 60-70 years of age and 70% of men 70-80 years of age have low bioavailable or free testosterone levels. Symptoms and findings of testosterone deficiency are similar to those associated with aging. They include loss of energy, depressed mood, decreased libido, erectile dysfunction, decreased muscle mass and strength, increased fat mass, frailty, osteopenia, and osteoporosis. Several small clinical trials indicate that testosterone replacement therapy can improve many of these findings; however, the studies have not been powered to assess potential risks, such as the need for invasive treatment of benign prostatic hyperplasia, development of a clinical prostate cancer, or cardiovascular events. Thus, the benefit/risk ratio of testosterone replacement therapy in aging men is not known.

Analysis of bidirectional pattern synchrony of concentration-secretion pairs: implementation in the human testicular and adrenal axes

The hypothalamo-pituitary-testicular and hypothalamo-pituitary-adrenal axes are prototypical coupled neuroendocrine systems. In the present study, we contrasted in vivo linkages within and between these two axes using methods without linearity assumptions. We examined 11 young (21–31 yr) and 8 older (62–74 yr) men who underwent frequent (every 2.5 min) blood sampling overnight for paired measurement of LH and testosterone and 35 adults (17 women and 18 men; 26–77 yr old) who underwent adrenocorticotropic hormone (ACTH) and cortisol measurements every 10 min for 24 h. To mirror physiological interactions, hormone secretion was first deconvolved from serial concentrations with a waveform-independent biexponential elimination model. Feedforward synchrony, feedback synchrony, and the difference in feedforward-feedback synchrony were quantified by the cross-approximate entropy (X-ApEn) statistic. These were applied in a forward (LH concentration template, examining pattern recurrence in testosterone secretion), reverse (testosterone concentration template, examining pattern recurrence in LH secretion), and differential (forward minus reverse) manner, respectively. Analogous concentration-secretion X-ApEn estimates were calculated from ACTH-cortisol pairs. X-ApEn, a scale- and model-independent measure of pattern reproducibility, disclosed 1) greater testosterone-LH feedback coordination than LH-testosterone feedforward synchrony in healthy men and significant and symmetric erosion of both feedforward and feedback linkages with aging; 2) more synchronous ACTH concentration-dependent feedforward than feedback drive of cortisol secretion, independent of gender and age; and 3) enhanced detection of bidirectional physiological regulation by in vivo pairwise concentration-secretion compared with concentration-concentration analyses. The linking of relevant biological input to output signals and vice versa should be useful in the dissection of the reciprocal control of neuroendocrine systems or even in the analysis of other nonendocrine networks.

Age-related differences in serum gonadotropin (FSH and LH), salivary testosterone, and 17-? estradiol levels among Ache Amerindian males of Paraguay

Age-related differences in serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), salivary testosterone, and 17-beta estradiol levels are reported for Ache Amerindian males (n = 17; mean age, 37.1 +/- 14.2 SD) of Paraguay in order to explore population variation in patterns of male reproductive senescence in a foraging/agricultural community. Hormone associations were examined to test various hypotheses for age-related differences in hypothalamic-pituitary function. Significant increases in FSH (r = 0.75, P < 0.0005) and LH (r = 0.65, P < 0.01) were noted in association with aging. No significant correlation was observed between morning or evening testosterone and age. Morning and evening estradiol levels were associated with morning and evening testosterone, respectively (morning, r = 0.53, P = 0.05; evening, r = 0.63, P = 0.02). Evening estradiol was also positively associated with LH (r = 0.66, P = 0.02), suggesting testicular production to be an important source of circulating estradiol. Morning estradiol tended to rise with age, but was not significant (r = 0.39, P = 0.15). Anthropometric measurements of height, weight, body mass index, and fat percent did not change significantly with age. In contrast to testosterone, age-related differences in gonadotropin levels may be independent of energetic status, less variant, and more universal among male populations. Implications for gonadotropin function and aging on human male reproductive senescence and life histories are discussed.

Waist circumference and testosterone levels in community dwelling men. The Tromsø study

To examine the relationship of total and free testosterone and sex hormone-binding globulin (SHBG) with central obesity in men, we studied 1548 men aged 25-84 years that took part in the 1994--1995 survey of the Tromsø study. Total testosterone and SHBG were measured by immuno-assay and the free testosterone fraction was calculated. These measurements were analyzed in relation to anthropometric data and lifestyle factors. The age-adjusted correlation between waist circumference (WC) and total testosterone was -0.34 (p < 0.001), between WC and free testosterone -0.09 (p < 0.001) and, between WC and SHBG -0.44 (p < 0.001). Adjusting for BMI and lifestyle factors weakened, but did not eliminate these associations. All hormone and SHBG associations were stronger for WC than for waist-hip ratio or BMI. In age- and BMI-adjusted analyses men with a WC > or = 102 cm had significantly lower levels of total testosterone and SHBG compared to men with an optimal WC, defined as < 94 cm (12.3 vs. 13.9 nmol/l; p < 0.01 and 48.5 vs. 55.1 nmol/l; p < 0.001, respectively). The lowest levels of total and free testosterone were observed in men with relatively high WC despite relatively low overall obesity (BMI), suggesting that WC should be the preferred anthropometric measurement in predicting endogenous testosterone levels.

Testosterone replacement therapy: current trends and future directions

Male hypogonadism is characterized by abnormally low serum testosterone levels associated with typical symptoms, including mood disturbance, sexual dysfunction, decreased muscle mass and strength, and decreased bone mineral density. By restoring serum testosterone levels to the normal range using testosterone replacement therapy, many of these symptoms can be relieved. For many years, injectable testosterone esters or surgically implanted testosterone pellets have been the preferred treatment for male hypogonadism. Recently, newer treatment modalities have been introduced, including transdermal patches and gels. The development of a mucoadhesive sustained-release buccal tablet is the latest innovation, which will provide patients with an additional option. The availability of new treatment modalities has helped to renew interest in the management of male hypogonadism, highlighting the need to address a number of important but previously neglected questions in testosterone replacement therapy. These include the risks and benefits of treatment in different patient populations (e.g. the elderly) and the need for evidence-based diagnosis and treatment monitoring guidelines. While some recommendations have been developed in individual countries, up-to-date, internationally accepted evidence-based guidelines that take into account national differences in clinical practice and healthcare delivery would optimize patient care universally.