Testosterone influences spatial cognition in older men

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.

Strategies and methods for research on sex differences in brain and behavior

Female and male brains differ. Differences begin early during development due to a combination of genetic and hormonal events and continue throughout the lifespan of an individual. Although researchers from a myriad of disciplines are beginning to appreciate the importance of considering sex differences in the design and interpretation of their studies, this is an area that is full of potential pitfalls. A female's reproductive status and ovarian cycle have to be taken into account when studying sex differences in health and disease susceptibility, in the pharmacological effects of drugs, and in the study of brain and behavior. To investigate sex differences in brain and behavior there is a logical series of questions that should be answered in a comprehensive investigation of any trait. First, it is important to determine that there is a sex difference in the trait in intact males and females, taking into consideration the reproductive cycle of the female. Then, one must consider whether the sex difference is attributable to the actions of gonadal steroids at the time of testing and/or is sexually differentiated permanently by the action of gonadal steroids during development. To answer these questions requires knowledge of how to assess and/or manipulate the hormonal condition of the subjects in the experiment appropriately. This article describes methods and procedures to assist scientists new to the field in designing and conducting experiments to investigate sex differences in research involving both laboratory animals and humans.

Sex differences in spatial visualization and episodic memory as a function of alcohol consumption

AIMS

Sex differences in visuospatial ability as well as episodic memory have been reliably demonstrated, irrespective of alcoholism. Studies in alcoholics have consistently documented cognitive deficits in visuospatial ability, problem solving and memory function. This cross-sectional, population-based study examined if sex differences in cognitive performance could be impacted by alcohol consumption.

METHODS

Drinking data were collected from 2224 randomly sampled adults, aged between 35 and 85 years, who participated in the Betula study on memory, health and aging. Participants were classified into non-, light, moderate and heavy drinking subgroups based on sex-adjusted normative values. Cognitive tasks demonstrating clear sex differences, such as episodic memory tasks (favouring women) and spatial visualization tasks (favouring men), were conducted and performance was assessed by sex and the drinking group.

RESULTS

After controlling for age and education, overall analyses found expected sex differences in episodic memory and spatial visualization that were apparent across the entire population. When these sex differences were examined by drinking group, visuospatial performance favouring men disappeared for the moderate to heavy drinking groups, but higher performance by women on episodic memory tasks was consistent across all levels of alcohol consumption. Traditional biomarkers of increased alcohol consumption (GGT and MCV) correlated with the reported drinks/day.

CONCLUSIONS

These results lend support to the theory that moderate alcohol intake may be beneficial to cognitive function in women, but not necessarily in men.

Age-related changes in hemispheric asymmetry depend on sex

A total of 92 participants, 50 younger (mean age 26.3 years) and 42 older (mean age 63.8 years), were tested for visual-field asymmetries. On a word-matching task, a right-visual-field (RVF) advantage increased with age, consistent with the theory that right-hemispheric function shows relatively greater decline with age than left-hemispheric function. On a figural-comparison task, a left-visual-field (LVF) advantage was marginally decreased with age in the men, but significantly increased in the women, probably because age-related changes in hormonal levels are more pronounced in women. This increase in LVF advantage is contrary to both the HAROLD theory that hemispheric asymmetry declines with age, and the theory of relative right-hemispheric decline.

Virtual navigation in humans: the impact of age, sex, and hormones on place learning

Certain cognitive processes, including spatial ability, decline with normal aging. Spatial ability is also a cognitive domain with robust sex differences typically favoring males. However, tests of spatial ability do not seem to measure a homogeneous class of processes. For many, mentally matching rotated three-dimensional images is the gold standard for measuring spatial cognition in humans, while the Morris water task (MWT) is a preferred method in the domain of nonhuman animal research. The MWT is sensitive to hippocampal damage, a structure critical for normal learning and memory and often implicated in age-related cognitive decline. A computerized (virtual) version of the MWT (VMWT) appears to require and engage human hippocampal circuitry, and has proven useful in studying sex differences and testing spatial learning theories. In Experiment 1, we tested participants (20-90 years of age) in the VMWT and compared their performance to that on the Vandenberg Mental Rotation Test. We report an age-related deficit in performance on both tasks. In Experiment 2, we tested young (age 20-39) and elderly (age >60) participants in the VMWT and correlated their performance to the circulating levels of testosterone and cortisol. Our findings indicate that the persistence of male spatial advantage may be related to circulating testosterone, but not cortisol levels, and independent of generalized age-related cognitive decline.

Effect of oral testosterone undecanoate on visuospatial cognition, mood and quality of life in elderly men with low-normal gonadal status

OBJECTIVES

The effects of supplemental testosterone on cognition, mood and wellbeing in ageing men are unclear. This study aimed to assess the effect of 12-months of oral testosterone supplementation on cognitive function, mood and quality of life in elderly men with low-normal gonadal status, not specifically selected for cognitive or mood defects.

METHODS

A standard oral dose (80 mg twice daily) of testosterone undecanoate (TU) or placebo was administered for one year to 76 healthy men 60 years or older. All men had a free testosterone index (FTI) of 0.3-0.5, which represents a value below the normal lower limit for young men (19-30 years), but remains within the overall normal male range. A neuropsychological assessment including the trail making test (part B), visuospatial (VSP) block design test, mini mental state exam (MMSE), Geriatric Depression Scale (GDS), a 5-point Likert and a 10-point visual analogue quality of life (QoL) scale, along with serum hormone measurements were obtained at baseline, 6, and 12 months.

RESULTS

Although calculated bioavailable testosterone (cBT) and FTI were higher, and muscle mass increased after 12 months, there was no difference in scores on the trail making or VSP block tests, the MMSE, GDS or either of the QoL scales between the testosterone and placebo group. There was no relationship between baseline cBT or FTI and treatment effect for any of the outcome measures.

CONCLUSIONS

12-month supplementation with oral TU does not affect scores on visuospatial tests or mood and quality of life scales in older men with low-normal gonadal status.

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.

Sex, Age, and Training Modulate Spatial Memory in the Rhesus Monkey (Macaca mulatta)

The authors tested 90 rhesus monkeys (Macaca mulatta) on a task of spatial memory, the spatial Delayed Recognition Span Test. The results showed that performance declined significantly with age, males had greater scores than females, and the rate of apparent decline with age was greater in males than in females. Both working and reference memory declined with age, but only working memory showed sex differences. The authors compared these data with that of 22 monkeys who were trained on a simpler version of the task before formal testing. Training had no effect on males but dramatically improved working memory in young females. The results confirm a male advantage in spatial working memory at a young age and confirm a greater decline with age in males than in females. It is important to note that prior training completely reverses the deficits of young females.

Sex Differences and Individual Differences in Cognitive Performance and Their Relationship to Endogenous Gonadal Hormones and Gonadotropins

Sexually dimorphic cognitive performance in men (n=42) and women (n=42) was related to testosterone, estradiol, progesterone, luteinizing hormone, follicle-stimulating hormone, and sex hormone binding globulin, measured in 10-ml blood samples collected between 0900 and 1030 and, among women, during the follicular phase of the menstrual cycle. Significant sex differences favored men on spatial tasks (Mental Rotation and Judgment of Line Orientation) and on an inhibition task and favored women on a verbal task (category fluency). However, there were no significant relationships between any of the hormones and cognitive performance, suggesting that there are few, if any, consistent, substantial relationships between endogenous, nonfluctuating levels of gonadal hormones or gonadotropins and these cognitive abilities in men or women.

The effect of intrahippocampal injection of testosterone enanthate (an androgen receptor agonist) and anisomycin (protein synthesis inhibitor) on spatial learning and memory in adult, male rats

In most mammals, the hippocampus has a well-documented role in spatial memory acquisition. High concentration of androgen receptors in fundamental centers of learning and memory in brain such as hippocampus shows that there may be some relationships between androgen receptors and cognitive aspects of brain. Previous studies, which have shown sex-dependent differences in hippocampal morphology and physiology, suggest a modulatory role for sex steroids in hippocampal function. Androgens have been shown to modulate some hippocampal-mediated behaviors including learning and memory. To study the mechanism of action of androgens in processes underlying learning and memory, anisomycin, a protein synthesis inhibitor was used to prevent the genomic effects of testosterone. Therefore, the effects of anisomycin and testosterone together were assessed on rat's performance in MWM. Rats received anisomycin (2.5 microg/0.5 microl), testosterone (80 microg/0.5 microl) or both anisomycin (2.5 microg/0.5 microl) and testosterone (80 microg/0.5 microl) through the connulas in the CA1 region. Anisomycin was injected 20 min and testosterone was injected 35 min before training each day. The results showed that anisomycin (2.5 microg/0.5 microl) and testosterone (80 microg/0.5 microl) increased latencies to find the invisible platform. But the group that received testosterone and anisomycin together was decrease in latency and traveled distance to find the invisible platform.

Testosterone administration attenuates regional brain hypometabolism in women with anorexia nervosa

Abnormalities in brain metabolism have not been consistently well localized in anorexia nervosa (AN), and effects of specific therapies on these functional abnormalities have not been studied. Androgen replacement therapy improves mood, well-being and cognitive function in men with androgen deficiency. We therefore hypothesized that women with AN and relative androgen deficiency would exhibit regional brain hypometabolism compared with healthy controls, and that low-dose physiologic androgen replacement would attenuate the hypometabolism in some of these brain loci. We used FDG PET and statistical parametric mapping methods to investigate regional brain glucose metabolism in (1) 14 women with AN and 20 healthy control subjects of similar mean age and (2) women with AN after randomization to low-dose replacement testosterone therapy or placebo. Cerebral metabolism was decreased in the posterior cingulate, pregenual anterior cingulate, left middle temporal, right superior temporal, and left dorsolateral prefrontal cortex in the AN group compared with controls. In AN patients receiving testosterone, cerebral metabolism increased in the posterior cingulate, subgenual anterior cingulate, premotor cortex, right caudate and right parietal lobes. In conclusion, our data demonstrate distinct loci of regional brain hypometabolism in women with AN compared with controls. Moreover, abnormalities in one of these regions-the posterior cingulate cortex-were attenuated towards normal with low-dose testosterone replacement therapy. Further study is warranted to replicate these findings, as well as to determine their physiological and clinical significance.

Treatment of androgen deficiency in the aging male

Although guidelines for androgen replacement therapy for older men have been developed by several groups, the data to support treatment are based on the results of only a small number of clinical trials. It has not been definitively established that the decline in testosterone seen in most aging men results in an androgen deficient state with health-related outcomes that can be improved by androgen therapy.

The aging male: testosterone deficiency and testosterone replacement. An up-date

The significance of the age-related decline of androgens remains unclear in terms of cardiovascular risk, mood and cognition, and prostatic health. Although much research has been undertaken in this area and men's health has received still more attention in the latest years, there are no data based on randomized controlled clinical studies in aging men investigating the long-term effects of androgen replacement therapy on various aspects of the cardiovascular system, the immune system, body composition, and the brain. In men receiving long-term androgen replacement therapy, the safety aspects regarding the prostate are also an area of clinical importance. In this paper we present an up-dated review of the experimental and clinical evidence of androgen deficiency and androgen replacement therapy on carbohydrate metabolism, on coagulation and fibrinolysis, inflammatory effects, effects on lipoprotein metabolism, direct arterial effects, effects on body composition, effects on cognitive function and mood, and prostatic effects. The evidence clearly shows that data for the most part are conflicting, with only very few randomized studies available.

Androgens and the ageing male

Serum testosterone levels peak in early adulthood in men and fall progressively with age. Since sex hormone binding globulin increases with age, the unbound forms of testosterone (free and bioavailable testosterone) fall more steeply than total testosterone levels. Serum testosterone levels below the normal range for young healthy adult males provide chemical evidence of androgen deficiency independent of the age of the patient. When accompanied by signs or symptoms that are compatible with androgen deficiency, treatment with testosterone should be considered in older men without evidence of prostate or breast cancer. While such therapy for younger hypogonadal men has shown benefit on libido, mood, muscle mass, muscle strength, bone mineral density and haematocrit, similar benefits in older men have not been as adequately assessed. While there is no convincing evidence that testosterone treatment in older men will increase the risk of cardiovascular or prostate cancer, long-term, well-controlled studies are lacking and needed. Treatment options for older men include injectable, transdermal and transbuccal testosterone preparations.

5alpha-reduced androgens may have actions in the hippocampus to enhance cognitive performance of male rats

Androgens may improve cognitive performance; however, these effects and mechanisms of androgens are not well understood. Whether testosterone's (T) effects on cognitive performance are mediated by its 5alpha-reduced, non-aromatizable metabolite dihydrotestosterone (DHT) and/or its 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) reduced metabolite 3alpha-androstanediol (3alpha-diol), was investigated. In Experiment 1, male rats that were gonadally intact, or gonadectomized (GDX) and DHT-replaced with a silastic capsule, had better performance in the inhibitory avoidance task, and higher plasma DHT and 3alpha-diol levels, compared to GDX rats. In Experiments 2-4, intra-hippocampal indomethacin, a 3alpha-HSD inhibitor, to intact or DHT-replaced, but not GDX, rats decreased performance in the inhibitory avoidance task and reduced hippocampal 3alpha-diol levels compared to that observed in rats with control implants. Thus, the 5alpha-reduced androgen DHT has cognitive-enhancing effects, independent of E(2), which are attenuated by a 3alpha-HSD inhibitor, indomethacin. These results suggest that 5alpha-reduced androgens may have actions in the hippocampus to improve cognitive performance.

One year follow-up study of the association between chemical castration, sex hormones, beta-amyloid, memory and depression in men

The results of several recent studies suggest that estrogen and testosterone play an important role in the modulation of mood and cognitive function in women, and preliminary evidence indicates that these hormones may also modulate the levels of beta-amyloid (Abeta), a 4 Kilo Dalton peptide that is likely to be involved in the pathogenesis of Alzheimer's disease. However, the physiological and clinical effects of reversible castration remain unclear and no systematic data is currently available for men. We designed the present study to investigate the effects of reversible chemical castration on the mood and cognitive performance of men treated for prostate cancer, as well as its impact on the levels of plasma Abeta. Forty men with prostate cancer were clinically treated with androgen blockade therapy (flutamide and leuprolide) for 36 weeks and subsequently followed up for another 18 weeks after treatment was discontinued. All subjects received a comprehensive clinical, neuropsychological and biochemical evaluation that included the use of the Beck Depression (BDI) and Anxiety Inventories (BAI), several subtests of the Wechsler Memory and Intelligence Scales (Word Lists-WL, Verbal Paired Associates-VPA, Visual Reproduction-VR and Block Design-BD), and biochemical monitoring of changes in estrogen, testosterone and Abeta levels. Chemical castration was associated with a rapid and marked decline in the levels of testosterone and estradiol, and significant increase in plasma Abeta levels. Treatment was associated with increased BDI (p = 0.004) and BAI scores (p < 0.001), although such changes were of questionable clinical significance (i.e., few subjects had scores > or = 13). CAMCOG (p = 0.046) and WL recall total scores (p < 0.001) improved significantly after androgen blockade treatment was discontinued, but visuospatial abilities, as assessed by BD, was not influenced by the introduction or discontinuation of treatment. There was a significant negative correlation between changes in Abeta levels and subjects' WL total score change between weeks 36 and 54 (r = -0.452, p = 0.012). The results of this naturalistic study indicate that chemical castration is associated with a significant rise in the plasma levels of Abeta and, clinically, with increased depression and anxiety scores. The discontinuation of treatment is associated with better cognitive performance, most noticeably of verbal memory. The performance of subjects on the WL test was negatively correlated with plasma levels of Abeta, but the clinical significance of this finding remains to be determined.

Serum testosterone, growth hormone, and insulin-like growth factor-1 levels, mental reaction time, and maximal aerobic exercise in sedentary and long-term physically trained elderly males

The aim of the study was to investigate the effect of regular exercise on maximum oxygen uptake capacity (VO2max), reaction time (RT), testosterone (T), growth hormone (GH), insulin-like growth factor-I (IGF-I) in athletes compared to sedentary controls. VO2max, RT, T, GH, and IGF-I levels were 31.2 +/- 6.2 ml/min/kg, 106.7 +/- 23.2 s, 8.3 +/- 1.3 ng/mL, 1.6 +/- 0.7 ng/mL, 106.5 +/- 27.0 ng/mL in master athlete group and 18.8 +/- 5.1 ml/min/kg, 148.3 +/- 39.3 s, 5.4 +/- 1.7 ng/mL, 0.8 +/- 0.3 ng/mL, 90.2 +/- 23.8 ng/mL in sedentary control group, respectively. The differences between regularly exercising males and the control group of sedentary males were found to be statistically significant. The results showed that long-term exercise decreased RT and increased VO2max, T, and GH in elderly males; elevated serum T and GH levels may be advantageous for brain functions.

Mnemonic effects of testosterone and its 5α-reduced metabolites in the conditioned fear and inhibitory avoidance tasks

Experiments were conducted to examine whether performance in hippocampally-mediated learning tasks is influenced by testosterone (T) and/or its 5alpha-reduced metabolites, dihydrotestosterone (DHT) and 3alpha-androstanediol (3alpha-diol). Performance in the conditioned fear and inhibitory avoidance tasks were examined in intact and gonadectomized (GDX), androgen-replaced rats. In Experiment 1, the behavior of intact and GDX rats in the conditioned fear paradigm were compared. GDX rats spent more time freezing, an index of increased learning, in the context, hippocampally-mediated task, but not in the cued, amygdala-mediated task. In Experiment 2, GDX rats were administered T, DHT, 3alpha-diol, estrogen (E2), or vehicle 1 mg/kg sc after training in the conditioned fear paradigm. T-, 3alpha-diol-, or E2-, compared with vehicle-administered rats, spent significantly more time freezing in the contextual, but not the cued, condition. In Experiment 3, intact compared with GDX rats had significantly longer crossover latencies, indicating better performance, in the inhibitory avoidance task. In Experiment 4, T, DHT, 3alpha-diol, or vehicle 1 mg/kg sc was administered to GDX rats immediately following training in the inhibitory avoidance task. Rats administered T, DHT, or 3alpha-diol had significantly longer crossover latencies compared with vehicle controls. In Experiment 5, androgen levels in the hippocampus were elevated 1 h following administration, when androgen exposure is essential for consolidation. These data indicate that androgens effects to enhance learning may be mediated in part by actions of 5alpha-reduced metabolites in the hippocampus.

Complications of androgen deprivation therapy in men with prostate cancer

Androgen deprivation therapy (ADT) is indicated for the treatment of metastatic prostate cancer and locally advanced disease. In addition to sexual side effects, long-term ADT results in several other changes, including hot flashes; gynecomastia; changes in body composition, metabolism, and the cardiovascular system; osteoporosis; anemia; psychiatric and cognitive problems; and fatigue and diminished quality of life. This review discusses these complications of ADT and treatments aimed at reducing them. It is important for clinicians to anticipate these effects and to initiate measures to prevent or minimize them in order to maintain quality of life in prostate cancer survivors.

Treatment of androgen deficiency in the aging male

Although guidelines for androgen replacement therapy for older men have been developed by several groups, the data to support treatment are based on the results of only a small number of clinical trials. It has not been definitively established that the decline in testosterone seen in most aging men results in an androgen deficient state with health-related outcomes that can be improved by androgen therapy.

Serum levels of estradiol and testosterone and performance in different cognitive domains in healthy elderly men and women

Sex hormones could protect against age-related cognitive decline in elderly men and women. We investigated the relationships between serum total testosterone (TT), total estradiol (TE2) levels and cognitive function in 145 non-demented elderly volunteers (aged 61-91 years) who were not using hormone replacement therapy (HRT). Women (n=66) were better at verbal recall than men (n=79) and men were slightly better at naming. There was a positive relationship between serum levels of TE2 and verbal list recall but not with other verbal memory tests (e.g. Verbal Paired Associates) in women. There was a negative relationship of serum TT levels with verbal recall. Surprisingly, women who were in the upper age tertile (> 77 years of age) were better at verbal recall than men and than women younger than 72; this effect was independent of hormone levels. Men between 61 and 72 years of age showed a positive relationship between high TE2 levels and Spatial Span performance and between high TT levels and speed of information processing, while for women of this age-group, a negative relationship was found. These preliminary results were unchanged when controlling for education, sex hormone binding globulin levels, body mass index, depression, daily alcohol use and smoking. In sum, not all cognitive functions were better with higher levels of sex steroids and effects seemed to be modified by sex; the sex-sensitive tests showing the clearest effects. More research is required to investigate whether there is a window of time in which hormone therapy could be beneficial for middle-aged men.

Effects of testosterone on behavior, depression, and cognitive function in older men with mild cognitive loss

BACKGROUND

The role of sex hormones in the prevention of cognitive decline is uncertain. Animal studies suggest mechanisms for sex hormones including testosterone to maintain optimal cognitive function. But, there are studies to suggest that endogenous testosterone levels are associated with aggression in men with cognitive impairment.

METHODS

In this pilot study, 11 men (mean age 80 +/- 5 years, range 73-87 years) with early cognitive decline and bioavailable testosterone levels below 128 ng/dl (lower limit for adult normal range) were randomized to receive intramuscular testosterone (200 mg every 3 weeks) or placebo for 12 weeks. Outcome measures included sex hormones (testosterone, bioavailable testosterone, sex hormone binding globulin, estradiol, and estrone), Behave AD Questionnaire, Katz Activities of Daily Living, Geriatric Depression Scale, Digit Span, Clock Face Drawing, Clock Face Perception, Verbal Fluency, Trail-Making B, and International Prostate Symptom Score at baseline, 4 weeks, and 10 weeks.

RESULTS

All men completed the study. Total and bioavailable testosterone, estrone, and estradiol levels increased in men receiving testosterone, but no changes were detected in men receiving placebo. No significant changes were found in behavior following testosterone supplementation, nor was there evidence of change in depression or activities of daily living. No discernable changes were found in any of the cognitive tests. Symptoms of prostate hyperplasia remained unchanged in the testosterone (6.6 + 5.8 to 5.2 + 3.6; p =.39) and placebo (8.8 + 6.4 to 6.4 + 3.8; p =.15) groups, and prostate-specific antigen levels did not change significantly.

CONCLUSION

No significant changes in behavior, function, depression, or cognitive performance occurred following 12 weeks of testosterone replacement in men with low testosterone levels and early-to-moderate cognitive impairment. This pilot work suggests that testosterone can be given to men with early cognitive impairment without significant concern about worsening aggressive or unwanted behaviors.

Sex differences in performance over 7 years on the Wechsler Intelligence Scale for Children--Revised among adults with intellectual disability

BACKGROUND

The aim of this study was to explore changes related to sex differences on the Wechsler Intelligence Scale for Children - Revised (WISC-R) subtest performance over a 7-year interval in middle-aged adults with intellectual disability (ID). Cognitive sex differences have been extensively studied in the general population, but there are few reports concerning individuals with ID. Sex differences are of current relevance to actively debated issues such as cognitive changes during menopause and risk for Alzheimer's disease. Given that hormonal effects on cognition have been observed in the general population, particularly in areas such as visuospatial processing, and individuals with Down's syndrome (DS) have been reported to be hormonally and reproductively atypical, we analysed our data to allow for the possibility of an aetiology-specific profile of sex differences for these adults.

METHODS

The WISC-R subtests were administered in a longitudinal study, as part of a more comprehensive test battery, at least twice within 7 years. Participants were 18 females with ID without DS [age at first test time (time 1): mean = 40.5; IQ: mean = 59.3], 10 males with ID without DS (age at time 1: mean = 42.4; IQ: mean = 59.4), 21 females with DS (age at time 1: mean = 37.9; IQ: mean = 51.6), and 21 males with DS (age at time 1: mean = 40.3; IQ: mean = 54.3). All participants were in the mild to moderate range of ID and were displaying no changes suggestive of early dementia.

RESULTS

Females, regardless of aetiology of ID, exhibited a robust superiority on the coding subtest, which parallels the widely reported difference among adults in the general population. Additionally, there was a decline in overall performance during the 7-year study interval, particularly on the verbal subscale subtests, but there was no evidence of sex-differentiated decline. There were also marginal sex by aetiology interactions on the object assembly and block design subtests, suggesting that males with unspecified ID might perform better than their female peers, but among adults with DS, females might do better than males.

CONCLUSIONS

This study supports the presence of cognitive sex differences in the population with ID as indicated by female superiority on the WISC-R coding subtest. Extending this observation to adults with ID has implications for explanations of female advantage on this task, which now have to account for its presence among individuals with a broader range of intellectual capabilities, more atypical developmental histories and more varied genotypes than previously considered. Trends towards sex by aetiology interactions on the two visuoconstructive subtests, while marginal, were sufficient to warrant continued consideration of the idea of a distinct profile of sex differences for adults with DS and to justify looking at the effects of sex separately within different aetiologies of ID.

Androgen Replacement Therapy

The major goal of androgen substitution is to replace testosterone at levels as close to physiological levels as is possible. For some androgen-dependent functions testosterone is a pro-hormone, peripherally converted to 5alpha-dihydrotestosterone (DHT) and 17beta-estradiol (E2), of which the levels preferably should be within normal physiological ranges. Furthermore, androgens should have a good safety profile without adverse effects on the prostate, serum lipids, liver or respiratory function, and they must be convenient to use and patient-friendly, with a relative independence from medical services. Natural testosterone is viewed as the best androgen for substitution in hypogonadal men. The reason behind the selection is that testosterone can be converted to DHT and E2, thus developing the full spectrum of testosterone activities in long-term substitution. The mainstays of testosterone substitution are parenteral testosterone esters (testosterone enantate and testosterone cipionate) administered every 2-3 weeks. A major disadvantage is the strongly fluctuating levels of plasma testosterone, which are not in the physiological range at least 50% of the time. Also, the generated plasma E2 is usually supraphysiological. A major improvement is parenteral testosterone undecanoate producing normal plasma levels of testosterone for 12 weeks, with normal plasma levels of DHT and E2 also. Subcutaneous testosterone implants provide the patient, depending on the dose of implants, with normal plasma testosterone for 3-6 months. However, their use is not widespread. Oral testosterone undecanoate dissolved in castor oil bypasses the liver via its lymphatic absorption. At a dosage of 80 mg twice daily, plasma testosterone levels are largely in the normal range, but plasma DHT tends to be elevated. For two decades transdermal testosterone preparations have been available and have an attractive pharmacokinetic profile. Scrotal testosterone patches generate supraphysiological plasma DHT levels, which is not the case with the nonscrotal testosterone patches. Transdermal testosterone gel produces fewer skin irritations than the patches and offers greater flexibility in dosage. Oromucosal testosterone preparations have recently become available. Testosterone replacement is usually of long duration and so patient compliance is of utmost importance. Therefore, the patient must be involved in the selection of type of testosterone preparation. Administration of testosterone to young individuals has almost no adverse effects. With increasing age the risk of adverse effects on the prostate, the cardiovascular system and erythropoiesis increases. Consequently, short-acting testosterone preparations are better suited for aging androgen-deficient men.

Testosterone's Analgesic, Anxiolytic, and Cognitive-Enhancing Effects May Be Due in Part to Actions of Its 5α-Reduced Metabolites in the Hippocampus

Although testosterone (T) may decrease anxiety and enhance cognitive performance, its mechanisms are not well understood. The authors hypothesized that if T's effects are mediated in part through actions of its 5alpha-reduced, nonaromatizable metabolite dihydrotestosterone (DHT) and/or its 3alpha-hydroxysteroid dehydrogenase reduced metabolite 3alpha-androstanediol (3alpha-diol) in the hippocampus, then T, DHT, and 3alpha-diol administration should produce similar behavioral effects concomitant with elevating T metabolites in the hippocampus. Gonadectomized male rats administered T, DHT, or 3alpha-diol via Silastic capsules or intrahippocampal infusions had greater analgesia (tail flick, paw lick), less anxiety behavior (plus-maze, open field, defensive freezing), and better learning (inhibitory avoidance) compared with vehicle control rats. Only 3alpha-diol levels in the hippocampus were consistently elevated in conjunction with these behavioral effects.

Relationship between testosterone supplementation and insulin-like growth factor-I levels and cognition in healthy older men

BACKGROUND

Our laboratory has previously reported that testosterone (T) administration to older men significantly improves cognitive function. This study examined potential changes in insulin-like growth factor (IGF) IGF-I, IGF-II and IGF-related binding proteins in response to T administration in older men and their relationship to cognitive functioning.

METHODS

Twenty-five healthy community dwelling volunteers, ranging in age from 50-80 years were randomized to receive weekly intra-muscular (i.m.) injections of either 100 mg T enanthate or placebo (saline) for 6 weeks. Serum hormone levels and cognitive functioning was assessed at baseline and twice during treatment.

RESULTS

Significant positive associations between IGF-I and IGF-II and spatial memory, spatial reasoning, and verbal fluency were observed after 6 weeks of T administration. Increased serum T levels from treatment were positively associated with improvement in spatial reasoning performance, whereas estradiol was associated with a decline in divided attention performance. Serum IGF-I, IGF-II and IGFBPs did not change in response to T treatment.

CONCLUSIONS

Our results suggest that T, estradiol and IGF-I may have independent and selective effects on cognitive functioning. Positive associations between T levels and cognition are consistent with an effect of androgen treatment, whereas positive associations between IGF-I levels and cognition are reflective of a relationship between endogenous IGF-I levels and cognition.

Role of androgens in mild cognitive impairment and possible interventions during andropause

Mild cognitive impairment (MCI) is becoming fashionable as a diagnosis, representing a state of cognitive decline associated with negligible functional loss. MCI is important as it often precedes Alzheimer's disease (AD). Recognizing MCI may lead to preventive strategies that can delay the onset of AD. Many patients who transition into andropause report problems with their memory. There is strong evidence from basic sciences and epidemiological studies that both estrogens and androgens play a protective role in neurodegeneration. The evidence from small prospective clinical trials lends support to the role of hormones in improving cognitive function. The improvement in cognitive function with hormones is subtle and often not measurable on standard neuropsychological batteries. Patients have reported memory improvements in both declarative and procedural domains after being on hormonal replacement. Functional changes and vascular changes can be detected after hormonal replacement with more sophisticated imaging of the brain like PET scans. We hypothesize androgens and perhaps selective androgen receptor modulators as future treatment options for MCI in aging males.

Androgen receptor CAG repeat polymorphism is associated with cognitive function in older men

BACKGROUND

Androgen receptors are located throughout the brain, especially in regions involved with learning and memory. Different lengths of a CAG (glutamine) repeat polymorphism in exon 1 of the androgen receptor gene may influence androgen action, with longer repeat lengths conferring decreased androgen sensitivity.

METHODS

We sought to determine if this CAG polymorphism was associated with cognition in older men.

RESULTS

Among 301 community-dwelling white men (mean age, 73.0 +/- 7.1), greater CAG repeat length was associated with lower scores on three cognitive tests (p <.05 for all). In addition, 12 participants (9.8%) had cognitive impairment in the low tertile of CAG repeat length whereas 29 (16.3%) had cognitive impairment in the two higher tertiles (odds ratio = 1.8; 95% confidence interval =.9-3.7).

CONCLUSIONS

Research should be directed at identifying the mechanism for this association and to determine if treatment with testosterone prevents cognitive decline.

Steroid hormones and neurosteroids in normal and pathological aging of the nervous system

Without medical progress, dementing diseases such as Alzheimer's disease will become one of the main causes of disability. Preventing or delaying them has thus become a real challenge for biomedical research. Steroids offer interesting therapeutical opportunities for promoting successful aging because of their pleiotropic effects in the nervous system: they regulate main neurotransmitter systems, promote the viability of neurons, play an important role in myelination and influence cognitive processes, in particular learning and memory. Preclinical research has provided evidence that the normally aging nervous system maintains some capacity for regeneration and that age-dependent changes in the nervous system and cognitive dysfunctions can be reversed to some extent by the administration of steroids. The aging nervous system also remains sensitive to the neuroprotective effects of steroids. In contrast to the large number of studies documenting beneficial effects of steroids on the nervous system in young and aged animals, the results from hormone replacement studies in the elderly are so far not conclusive. There is also little information concerning changes of steroid levels in the aging human brain. As steroids present in nervous tissues originate from the endocrine glands (steroid hormones) and from local synthesis (neurosteroids), changes in blood levels of steroids with age do not necessarily reflect changes in their brain levels. There is indeed strong evidence that neurosteroids are also synthesized in human brain and peripheral nerves. The development of a very sensitive and precise method for the analysis of steroids by gas chromatography/mass spectrometry (GC/MS) offers new possibilities for the study of neurosteroids. The concentrations of a range of neurosteroids have recently been measured in various brain regions of aged Alzheimer's disease patients and aged non-demented controls by GC/MS, providing reference values. In Alzheimer's patients, there was a general trend toward lower levels of neurosteroids in different brain regions, and neurosteroid levels were negatively correlated with two biochemical markers of Alzheimer's disease, the phosphorylated tau protein and the beta-amyloid peptides. The metabolism of dehydroepiandrosterone has also been analyzed for the first time in the aging brain from Alzheimer patients and non-demented controls. The conversion of dehydroepiandrosterone to Delta5-androstene-3beta,17beta-diol and to 7alpha-OH-dehydroepiandrosterone occurred in frontal cortex, hippocampus, amygdala, cerebellum and striatum of both Alzheimer's patients and controls. The formation of these metabolites within distinct brain regions negatively correlated with the density of beta-amyloid deposits.

Andropause:

There is increasing evidence that the common condition of hypogonadism in older men when associated with symptoms responds well to testosterone replacement. Over the last few years there has been a marked increase in the awareness and treatment of the andropause [137]. Long-term side effects of testosterone are uncertain with only eight people over 50 years having been studied for 10 years [138]. Testosterone needs to be considered a quality-of-life drug, similar to sildenafil, and at present it should be used only if it produces symptomatic improvement. There is a need for a men's health study to determine the long-term efficacy and safety of testosterone replacement in older persons.

Testosterone and behavior

In older men and women testosterone clearly improves libido and perhaps sexual activity. A number of authors have tried to describe a set of behavioral symptoms associated with the andropause. In older women testosterone seems to decrease dysphoria. In men the effects of testosterone on mood are less clear. In older men testosterone enhances spatial memory and possibly verbal and working memory. Table 2 summarizes the putative behavioral effects of testosterone. [Table: see text] There is a clear need for better designed large-scale behavioral studies to determine the effects of testosterone in older men and women.

Cognitive changes associated with supplementation of testosterone or dihydrotestosterone in mildly hypogonadal men: a preliminary report

This study prospectively examined changes in cognition in hypogonadal men given testosterone (T) or older hypogonadal men given dihydrotestosterone (DHT) gel. A battery of cognitive tests assessing verbal and spatial memory, language, and attention was administered at baseline (prior to medication) and again at days 90 and 180 of treatment for men receiving T gel and at baseline and days 30 and 90 of treatment for men receiving DHT gel. For men receiving T gel, circulating total T and estradiol (E(2)) were significantly raised compared with baseline, and a significant improvement in verbal memory was observed. For men receiving DHT gel, serum DHT levels increased and T levels decreased significantly compared with baseline, and a significant improvement in spatial memory was observed. The results suggest that beneficial changes in cognition can occur in hypogonadal men using T replacement levels and DHT treatment, and these changes in cognition can be reliably measured during a relative steady-state dose level. Further, our results suggest that aromatization of T to E(2) may regulate verbal memory in men, whereas nonaromatizable androgens may regulate spatial memory.

Gedächtnisleistung im Alter:

Zusammenfassung. Das höhere Lebensalter ist durch zahlreiche Veränderungen des Hormonsystems charakterisiert. Besonders markant ist die Abnahme der Sexualsteroidhormone (Östradiol, Progesteron, Testosteron, DHEA), während die basalen Spiegel des “Stresshormons“ Cortisol stabil bleiben oder leicht ansteigen. Die vorliegende Übersichtsarbeit diskutiert die Relevanz dieser hormonellen Veränderungen für Funktion und Struktur des Gehirns am Beispiel der Gedächtnisleistung im höheren Lebensalter. Bei älteren Frauen wurden wiederholt gedächtnisverbessernde und neuroprotektive Effekte von Östradiol berichtet. Inwieweit und in welche Richtung Progesteron die Östrogeneffekte moduliert, ist noch unklar, da sowohl synergistische als auch antagonistische Effekte berichtet wurden. Die Rolle des Testosterons für die Gedächtnisleistung des alternden Mannes ist bisher kaum untersucht. Mehrere Studien haben hingegen gezeigt, dass DHEA bei gesunden älteren Männern und Frauen keine positiven Effekte auf die Gedächtnisleistung ausübt. Das Nebennierenrindenhormon Cortisol verschlechtert akut Leistungen des Arbeitsgedächtnisses und des deklarativen Gedächtnisses. Darüber hinaus gibt es vermehrt Hinweise darauf, dass erhöhte basale Cortisolspiegel im Alter sowohl zu einer Verschlechterung der Gedächtnisleistung als auch zu einer Verringerung des Hippocampusvolumens führen. Zusammengenommen verdeutlichen diese Befunde, dass Steroidhormone die Struktur und Funktion des menschlichen zentralen Nervensystems nachhaltig beeinflussen.

Testosterone, but not nonaromatizable dihydrotestosterone, improves working memory and alters nerve growth factor levels in aged male rats

Recent studies have suggested that testosterone levels are lower in men with Alzheimer's disease and that testosterone treatment improves cognition in older men. Since testosterone can be aromatized to estrogen, testosterone's effects could be due to conversion into estrogen. We treated aged male rats with either testosterone or dihydrotestosterone (DHT), the latter of which is not aromatized to estrogen, in order to determine whether these treatments improve spatial working and reference memory as assessed in the water radial arm maze. We also tested whether such effects are related to beta-amyloid levels in the hippocampus or neurotrophin levels in the hippocampus, entorhinal cortex, frontal cortex, or striatum. Aged rats made more errors than young rats on all memory measures. Testosterone, but not DHT, improved working memory and decreased hippocampal NGF protein in aged rats, while having no effect on beta-amyloid. However, higher beta-amyloid levels were correlated with poorer working memory performance in young rats. Neurotrophin levels in entorhinal cortex were positively correlated with errors for all memory measures in androgen-treated rats. Similar to findings in human studies, in our study androgen treatment lowered circulating estradiol levels in aged rats, suggesting that androgen treatment exerts feedback to the hypothalamic pituitary axis and that conversion to estrogen may not be the underlying biological mechanism of testosterone's effects on memory and growth factor levels. The ratio of estradiol to testosterone, or the actions of the aromatase enzyme itself, may be responsible for the observed effects. These data support the hypothesis that testosterone therapy in aging men may provide positive effects on cognition and that neural regions that are linked to cognition, such as the hippocampus and/or entorhinal cortex, may be involved in such effects.

Androgen deficiency in the aging male: benefits and risks of androgen supplementation

There is now convincing evidence that in a subset of aging men, increasing with age, plasma testosterone levels fall below a critical level resulting in hypogonadism. This state of testosterone deficiency has an impact on bone, muscle and brain function and is maybe a factor in the accumulation of visceral fat which again has a significant impact on the cardiovascular risk profile. From the above it follows that androgen replacement to selected men with proven androgen deficiency will have beneficial effects. There is, however a concern that androgen administration to aging men may be harmful in view of effects on prostate disease. Benign prostate hyperplasia (BPH) and prostate cancer are typically diseases of the aging male, steeply increasing with age. But epidemiological studies provide no clues that the levels of circulating androgen are correlated with or predict prostate disease. Similarly, androgen replacement studies in men do not suggest that these men suffer in a higher degree from prostate disease than control subjects. It seems a defensible practice to treat aging men with androgens if and when they are testosterone-deficient, but long-term studies including sufficient numbers of men are needed.

Androgen treatment of male hypogonadism in older males

The treatment of primary and secondary hypogonadism with testosterone is well established. Recently, there has been increased awareness that low testosterone levels also occur in chronically ill persons and aging males. Because of sex hormone binding globulin changes, it is more appropriate to make the diagnosis using either free or bioavailable testosterone. A small number of controlled studies have suggested that testosterone replacement in older men improves libido, quality of erections, some aspects of cognition, muscle mass, muscles strength, and bone mineral density. It also decreases fat mass and leptin levels. A number of screening questionnaires for the andropause have been developed. Insufficient numbers of older men have been treated with testosterone to characterize the true incidence of side effects. There is a desperate need for well designed, large controlled trials to establish the value or otherwise of testosterone treatment in older males.

An integrative review on current evidence of testosterone replacement therapy for the andropause

OBJECTIVES

This paper examines the evidence supporting testosterone replacement in aging males. Confounding factors contributing to low testosterone levels and challenges to diagnosis of the andropause will also be considered.

METHODS

A thorough review using an integrative approach citing published literature and the ongoing work of the authors. A search was performed using National Library of Medicine PubMed. Electronic and print journals available at the Texas Medical Center library were also considered.

RESULTS

Information based on collective trials in older men has added to evidence for benefits and side effects of testosterone replacement inferred from studies in younger hypogonadal patients and animal models. In general, most investigators agree with short-term safety but long-term safety is unknown. Testosterone therapy in aging males improves body composition, certain domains of brain function and may also decrease cardiovascular risk in biological models. Measurable clinical effects are less apparent. Potential risks include erythrocytosis, edema, gynecomastia, and prostate stimulation. The possibility of increased risk of clinically significant prostate cancer and cardiovascular disease has been considered.

CONCLUSION

The search continues for an ideal replacement androgen and larger long-term studies are needed. At this time, androgen replacement is on a case-by-case basis and prostate cancer screening should be completed prior to instituting therapy. Routine androgen replacement therapy for aging males will have significant economic implications, and is not currently recommended.

The study of spatial memory in adult male rats with injection of testosterone enanthate and flutamide into the basolateral nucleus of the amygdala in Morris water maze

Extensive evidence suggests that the amygdala is involved in memory. The presence of androgenic and estrogenic receptors in the amygdala may reflect a possible involvement in certain activities of this part of the brain. Since sex steroids are known to play role in the maintenance and modulation of behavior, particularly spatial cognition throughout the life span, it was interesting to explore the role of these receptors in spatial memory. Therefore, an experiment was designed to investigate the effect of testosterone enanthate as an agonist and flutamide as an antagonist of androgenic receptors on spatial memory and learning. Wistar rats were bilaterally cannulated into basolateral nucleus of amygdala. Animals in different groups including vehicle (dimethyl sulfoxide) were proven to be inert for memory and learning. Testosterone enanthate (20, 40, 80 and 120 microg/0.5 microl), and flutamide (2, 5, 10, 20 and 40 microg/0.5 microl) were injected in both cannulae 30 min before each training day. After 4 days of experiments, results indicate a dose-dependent increase in parameters of escape latencies and travel distances to find the invisible platform in the group that received 120 microg/0.5 microl testosterone enanthate as compared to the control and vehicle groups. Flutamide had no effect on spatial memory. Therefore, it appears that androgens may effect memory and learning in amygdala. This is a feature that requires further investigation.

Role of androgens in mild cognitive impairment and possible interventions during andropause

Mild cognitive impairment (MCI) is becoming fashionable as a diagnosis, representing a state of cognitive decline associated with negligible functional loss. MCI is important as it often precedes Alzheimer's disease (AD). Recognizing MCI may lead to preventive strategies that can delay the onset of AD. Many patients who transition into andropause report problems with their memory. There is strong evidence from basic sciences and epidemiological studies that both estrogens and androgens play a protective role in neurodegeneration. The evidence from small prospective clinical trials lends support to the role of hormones in improving cognitive function. The improvement in cognitive function with hormones is subtle and often not measurable on standard neuropsychological batteries. Patients have reported memory improvements in both declarative and procedural domains after being on hormonal replacement. Functional changes and vascular changes can be detected after hormonal replacement with more sophisticated imaging of the brain like positron emission tomography (PET) scans. We hypothesize androgens and perhaps selective androgen receptor modulators as future treatment options for MCI in aging males.

Can estrogen play a significant role in the prevention of Alzheimer's disease?

In women the abrupt decline estrogen levels at menopause may be associated with cognitive deficits and increased risk for Alzheimer's disease (AD); estrogen replacement therapy may reduce this risk. Animal studies indicate that estrogen modulates neurotransmitter systems, regulates synaptogenesis, and is neuroprotective. These beneficial effects occur in brain areas critical to cognitive function and involved in AD. Reduced estrogen levels can compromise neuronal function and survival. Estrogen replacement therapy can reverse cognitive deficits associated with low estrogen levels and may reduce the risk of AD. However, clinical trials for estrogen replacement in the treatment of AD have produced ambiguous results. Initial, small, open-label and double blind clinical trials indicated improved cognitive function in women with AD. Recent large trials failed to show a beneficial effect for long-term estrogen replacement for women with AD. There are several variables that could affect these results, such as genetic factors, time between estrogen loss and replacement, extent and types of AD pathology, and other environmental and health factors. Presently large prospective studies are being conducted as the National Institutes of Health in the Women's Health Initiative and the Preventing Postmenopausal Memory Loss and Alzheimer's with Replacement Estrogens studies to provide a better assessment of the role of estrogen for age related health issues, including dementia.

Testosterone supplementation therapy for older men: potential benefits and risks

Serum testosterone levels decline gradually and progressively with aging in men. Many manifestations associated with aging in men, including muscle atrophy and weakness, osteoporosis, reduced sexual functioning, and increased fat mass, are similar to changes associated with testosterone deficiency in young men. These similarities suggest that testosterone supplementation may prevent or reverse the effects of aging. A MEDLINE search was performed to identify studies of testosterone supplementation therapy in older men. A structured, qualitative review was performed of placebo-controlled trials that included men aged 60 and older and evaluated one or more physical, cognitive, affective, functional, or quality-of-life outcomes. Studies focusing on patients with severe systemic diseases and hormone deficiencies related to specific diseases were excluded. In healthy older men with low-normal to mildly decreased testosterone levels, testosterone supplementation increased lean body mass and decreased fat mass. Upper and lower body strength, functional performance, sexual functioning, and mood were improved or unchanged with testosterone replacement. Variable effects on cognitive function were reported, with improvements in some cognitive domains (e.g., spatial, working, and verbal memory). Testosterone supplementation improved exercise-induced coronary ischemia in men with coronary heart disease, whereas angina pectoris was improved or unchanged. In a few studies, men with low testosterone levels were more likely to experience improvements in lumbar bone mineral density, self-perceived functional status, libido, erectile function, and exercise-induced coronary ischemia with testosterone replacement than men with less marked testosterone deficiency. No major unfavorable effects on lipids were reported, but hematocrit and prostate specific antigen levels often increased. Based on these results, testosterone supplementation cannot be recommended at this time for older men with normal or low-normal testosterone levels and no clinical manifestations of hypogonadism. However, testosterone replacement may be warranted in older men with markedly decreased testosterone levels, regardless of symptoms, and in men with mildly decreased testosterone levels and symptoms or signs suggesting hypogonadism. The long-term safety and efficacy of testosterone supplementation remain uncertain. Establishment of evidence-based indications will depend on further demonstrations of favorable clinical outcomes and symptomatic, functional, and quality-of-life benefits in carefully performed, long-term, randomized, placebo-controlled clinical trials.

Testosterone deficiency and mood in aging men: pathogenic and therapeutic interactions

In contrast to women, men do not experience a sudden cessation of gonadal function comparable to menopause. However, there is a progressive reduction in hypothalamic-pituitary-gonadal (HPG) function in aging men: testosterone (T) levels decline through both central (pituitary) and peripheral (testicular) mechanisms and there is a loss of the circadian rhythm of T secretion. In cohorts of men 75 years of age, mean plasma T levels are 35% lower than comparable young men, and more than 25% of men over 75 appear to be T-deficient. Such age-associated T deficiency, which has been termed 'andropause', is thought to be responsible for a variety of symptoms experienced by elderly men, such as weakness, fatigue, reduced muscle and bone mass, impaired haematopoiesis, oligospermia, sexual dysfunction, depression, anxiety, irritability, insomnia and memory impairment. However, it has been difficult to establish correlations between these symptoms and plasma T levels. Nevertheless, there is some evidence that T replacement leads to symptom relief, particularly with respect to muscle strength, bone mineral density, and haematopoiesis. Studies to date on the specific association between psychiatric symptoms, such as depressed mood, and T levels have been methodologically flawed. Overall, data suggest that although hypogonadism is not central to major depressive disorder (MDD), HPG hypofunction may have aetiological importance in mild depressive conditions, such as dysthymia.

Androgens and aging men

This article underlines the hormonal and clinical events characterizing the so-called andropause, as they may be described from an extensive review of the literature and some data obtained with the French colleagues of the author. Evidence-based hormonal intervention has to be positioned against anti-aging entrepreneurs who peddle hormones at random. The desequilibrium in aging men between the unchanged level of plasma cortisol and the profound decrease of androgens deserves cautious studies to eventually oppose this unbalanced hormonal situation effectively and safely.

Sex differences, laterality, and hormonal regulation of androgen receptor immunoreactivity in rat hippocampus

Sex differences, laterality, and hormonal regulation of androgen receptor (AR) immunoreactivity in rat hippocampal CA1 pyramidal cells were examined using the PG21 antibody. Adult male rats were either castrated or sham-operated at least 2 weeks prior to sacrifice. Gonadally intact females were sacrificed on the day of proestrus. Animals received an injection of either testosterone propionate (TP) or vehicle 2 h prior to sacrifice. Within CA1, both the intensity of staining and the number of AR+ cells were assessed. AR immunostaining was detected in all the groups with marked variation among them. The overall ranking of staining intensity was: gonadally intact males > females given TP > castrated males given TP > females > castrated males given vehicle. The number of AR+cells within subregions of CA1 showed the same basic pattern: among control-treated animals, gonadally intact males have more than females, but castrated males have the least, and acute TP treatment increases the number in both sexes. The increased level of AR immunoreactivity in CA1 of castrated males following acute TP treatment suggests that testicular androgens in adulthood normally increase AR immunoreactivity there, producing a sex difference favoring males in gonadally intact animals. We also found a higher number of AR+ CA1 cells on the left than on the right, but only in gonadally intact males and in females given TP. These results suggest that a laterality of AR distribution in the rat hippocampus may lead to lateralities in hippocampal structure and function.

The relationship between testosterone and route-learning strategies in humans

The relationships between route-learning strategies and circulating testosterone and estradiol levels were investigated in men and women. Testosterone and estradiol concentrations were measured by salivary assays and route-learning strategies were assessed using a direction-giving paradigm based on a novel map. Testosterone was positively correlated with the use of male-biased route-learning strategies in men, but not in women. These findings suggest sex-specific patterns of relationships between circulating testosterone and spatial processing, which apply to everyday spatial behavior.

Estrogen and Alzheimer's disease: the story so far

The ovarian hormone estrogen has long been used to treat the physical symptoms of menopause and to aid in the prevention of osteoporosis in postmenopausal women. Cumulative evidence from basic science and clinical research suggests that estrogen also plays a significant neuromodulatory and neuroprotective role. The numerous estrogenic effects in the brain include the modulation of synaptogenesis, increased cerebral blood flow, mediation of important neurotransmitters and hormones, protection against apoptosis, anti-inflammatory actions, and antioxidant properties. These multiple actions in the central nervous system support estrogen as a potential treatment for the cognitive decline associated with Alzheimer's disease (AD), the most common form of dementia. Evidence from epidemiological studies supports enhanced cognitive function in women with AD taking estrogen replacement therapy (ERT) as well as a reduced risk for developing AD in healthy women receiving ERT. Additional clinical evidence suggests that estrogen may modulate specific cognitive functions such as working memory and verbal learning and memory. However, results from more recent controlled trials have not consistently shown a beneficial effect of estrogen on the cognitive function of women with AD. Future research should focus on examining the influence of multiple potential mediators of ERT including the route of estrogen administration, form of estrogen (conjugated estrogens vs estradiol), duration of treatment, opposed versus unopposed estrogen and the use of estrogen analogues. Further, sensitive neuropsychological measures may provide more detailed information concerning the specific effects of estrogen on cognitive function. These important issues must be addressed in order to establish the role of estrogen for the prevention and treatment of AD in women.