Testosterone dose-response relationships in healthy young men

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.

Effects of Androgenic-Anabolic Steroids in Athletes

Androgenic-anabolic steroids (AAS) are synthetic derivatives of the male hormone testosterone. They can exert strong effects on the human body that may be beneficial for athletic performance. A review of the literature revealed that most laboratory studies did not investigate the actual doses of AAS currently abused in the field. Therefore, those studies may not reflect the actual (adverse) effects of steroids. The available scientific literature describes that short-term administration of these drugs by athletes can increase strength and bodyweight. Strength gains of about 5-20% of the initial strength and increments of 2-5 kg bodyweight, that may be attributed to an increase of the lean body mass, have been observed. A reduction of fat mass does not seem to occur. Although AAS administration may affect erythropoiesis and blood haemoglobin concentrations, no effect on endurance performance was observed. Little data about the effects of AAS on metabolic responses during exercise training and recovery are available and, therefore, do not allow firm conclusions. The main untoward effects of short- and long-term AAS abuse that male athletes most often self-report are an increase in sexual drive, the occurrence of acne vulgaris, increased body hair and increment of aggressive behaviour. AAS administration will disturb the regular endogenous production of testosterone and gonadotrophins that may persist for months after drug withdrawal. Cardiovascular risk factors may undergo deleterious alterations, including elevation of blood pressure and depression of serum high-density lipoprotein (HDL)-, HDL2- and HDL3-cholesterol levels. In echocardiographic studies in male athletes, AAS did not seem to affect cardiac structure and function, although in animal studies these drugs have been observed to exert hazardous effects on heart structure and function. In studies of athletes, AAS were not found to damage the liver. Psyche and behaviour seem to be strongly affected by AAS. Generally, AAS seem to induce increments of aggression and hostility. Mood disturbances (e.g. depression, [hypo-]mania, psychotic features) are likely to be dose and drug dependent. AAS dependence or withdrawal effects (such as depression) seem to occur only in a small number of AAS users. Dissatisfaction with the body and low self-esteem may lead to the so-called 'reverse anorexia syndrome' that predisposes to the start of AAS use. Many other adverse effects have been associated with AAS misuse, including disturbance of endocrine and immune function, alterations of sebaceous system and skin, changes of haemostatic system and urogenital tract. One has to keep in mind that the scientific data may underestimate the actual untoward effects because of the relatively low doses administered in those studies, since they do not approximate doses used by illicit steroid users. The mechanism of action of AAS may differ between compounds because of variations in the steroid molecule and affinity to androgen receptors. Several pathways of action have been recognised. The enzyme 5-alpha-reductase seems to play an important role by converting AAS into dihydrotestosterone (androstanolone) that acts in the cell nucleus of target organs, such as male accessory glands, skin and prostate. Other mechanisms comprises mediation by the enzyme aromatase that converts AAS in female sex hormones (estradiol and estrone), antagonistic action to estrogens and a competitive antagonism to the glucocorticoid receptors. Furthermore, AAS stimulate erythropoietin synthesis and red cell production as well as bone formation but counteract bone breakdown. The effects on the cardiovascular system are proposed to be mediated by the occurrence of AAS-induced atherosclerosis (due to unfavourable influence on serum lipids and lipoproteins), thrombosis, vasospasm or direct injury to vessel walls, or may be ascribed to a combination of the different mechanisms. AAS-induced increment of muscle tissue can be attributed to hypertrophy and the formation of new muscle fibres, in which key roles are played by satellite cell number and ultrastructure, androgen receptors and myonuclei.

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.

Testosterone metabolism, dose-response relationships and receptor polymorphisms: selected pharmacological/toxicological considerations on benefits versus risks of testosterone therapy in men

In this review selected toxicological problems related to testosterone therapy in hypogonadal men are discussed. Applying "classical" pharmacological/toxicological findings (e.g. animal studies on short- and long-term toxicity) to clinical situations is not very helpful. Molecular biological knowledge and especially evaluation of epidemiological studies, as well as intervention studies, on testosterone therapy in hypogonadal men are more useful. Potential risks include overdosage for lifestyle reasons, e.g. excessive muscle building and reduction of visceral obesity, when erythrocytosis occurs concomitantly. Modern galenic formulations of testosterone administration (e.g. transdermal gel, suitable testosterone esters for intramuscular application and newer oral preparations) avoid supraphysiological serum concentrations, therefore significantly reducing the toxicological risk. A hypothetical model of the toxicological risks of testosterone therapy is given that is based on the influence of testosterone metabolism (aromatization vs. reduction) of the respective parameter/target chosen. Finally, the great influence of polymorphisms of the androgen receptor on the assessment of toxicological risk and on the individualization of androgen therapy is shown. Already existing national, continental and international guidelines or recommendations for the testosterone therapy should be harmonized.

The Mechanisms of Androgen Effects on Body Composition: Mesenchymal Pluripotent Cell as the Target of Androgen Action

Testosterone supplementation increases muscle mass primarily by inducing muscle fiber hypertrophy; however, the mechanisms by which testosterone exerts its anabolic effects on the muscle are poorly understood. The prevalent view is that testosterone improves net muscle protein balance by stimulating muscle protein synthesis, decreasing muscle protein degradation, and improving the reutilization of amino acids. However, the muscle protein synthesis hypothesis does not adequately explain testosterone-induced changes in fat mass, myonuclear number, and satellite cell number. We postulate that testosterone promotes the commitment of pluripotent stem cells into the myogenic lineage and inhibits their differentiation into the adipogenic lineage. The hypothesis that the primary site of androgen action is the pluripotent stem cell provides a unifying explanation for the observed reciprocal effects of testosterone on muscle and fat mass.

Testosterone Supplementation for Aging-Associated Sarcopenia

Aging of humans is associated with a loss of muscle mass and function, and an increase in fat mass. Epidemiologic studies have demonstrated a correlation between bioavailable testosterone concentrations and fat-free mass and muscle strength. Testosterone replacement in older men with low testosterone levels increases fat-free mass and muscle strength, and decreases fat mass. However, we do not know whether testosterone replacement improves physical function and other health-related outcomes, or reduces the risk of disability, falls, or fractures in older men with low testosterone levels. The long-term risks and benefits of testosterone supplementation in older men are not known.

Treatment with oxandrolone and the durability of effects in older men

We investigated the effects of the anabolic androgen, oxandrolone, on lean body mass (LBM), muscle size, fat, and maximum voluntary muscle strength, and we determined the durability of effects after treatment was stopped. Thirty-two healthy 60- to 87-yr-old men were randomized to receive 20 mg oxandrolone/day (n = 20) or placebo (n = 12) for 12 wk. Body composition [dual-energy X-ray absorptiometry (DEXA), magnetic resonance imaging, and (2)H(2)O dilution] and muscle strength [1 repetition maximum (1 RM)] were evaluated at baseline and after 12 wk of treatment; body composition (DEXA) and 1-RM strength were then assessed 12 wk after treatment was discontinued (week 24). At week 12, oxandrolone increased LBM by 3.0 +/- 1.5 kg (P < 0.001), total body water by 2.9 +/- 3.7 kg (P = 0.002), and proximal thigh muscle area by 12.4 +/- 8.4 cm(2) (P < 0.001); these increases were greater (P < 0.003) than in the placebo group. Oxandrolone increased 1-RM strength for leg press by 6.7 +/- 6.4% (P < 0.001), leg flexion by 7.0 +/- 7.8% (P < 0.001), chest press by 9.3 +/- 6.7% (P < 0.001), and latissimus pull-down exercises by 5.1 +/- 9.1% (P = 0.02); these increases were greater than placebo. Oxandrolone reduced total (-1.9 +/- 1.0 kg) and trunk fat (-1.3 +/- 0.6 kg; P < 0.001), and these decreases were greater (P < 0.001) than placebo. Twelve weeks after oxandrolone was discontinued (week 24), the increments in LBM and muscle strength were no longer different from baseline (P > 0.15). However, the decreases in total and trunk fat were sustained (-1.5 +/- 1.8, P = 0.001 and -1.0 +/- 1.1 kg, P < 0.001, respectively). Thus oxandrolone induced short-term improvements in LBM, muscle area, and strength, while reducing whole body and trunk adiposity. Anabolic improvements were lost 12 wk after discontinuing oxandrolone, whereas improvements in fat mass were largely sustained.

Pharmacokinetics and degree of aromatization rather than total dose of different preparations determine the effects of testosterone: a nonhuman primate study in Macaca fascicularis

Currently available testosterone (T) preparations differ substantially in their pharmacokinetic profile that might influence their androgenic properties in terms of suppression of the gonadal axis, effects on anabolic parameters, lipid metabolism, and erythropoiesis. The present work was undertaken to determine the physiological effects of three T preparations with different serum kinetics. Twenty adult male cynomolgus monkeys (Macaca fascicularis) were randomly assigned to receive treatment for 28 weeks with either T enanthate (TE) every 4 weeks, T buciclate (TB) every 7 weeks, or T undecanoate (TU) every 10 weeks or remaining untreated (controls). Each injection delivered 20 mg pure T per kilogram body weight. Pharmacokinetic profiles demonstrated higher peak levels of T for TE-treated animals; serum half-lives were longer for TU or TB. Estradiol levels (area under the curve) were significantly higher in TB vs TU or TE. All T regimens suppressed serum luteinizing hormone bioactivity and testicular volumes declined (all P <.001 vs controls). Sperm counts were markedly lowered in all animals but least in TE (P <.01 vs TB or TU). During recovery phase, return to normal for all three parameters occurred significantly earlier in TE-treated animals, followed by those given TU, compared with TB (all P <.001 between groups). Body weight increased significantly during T exposure. This effect was stronger and more sustained in TB vs TU or TE (both P <.001). Serum creatinine and hemoglobin increased with high significance in all T-treated animals (all P <.001 vs controls). The lowering impact of T on serum lipids was markedly stronger in the longer-acting T preparations in comparison with TE, as were effects on purine metabolism (all P <.001). The pattern of exposure and degree of aromatization rather than overall exposure to T determine its effects in the preclinical primate model. Both fluctuations of androgen concentrations and the conversion rate to estradiol influence gonadal suppression as well as metabolism. These results have to be considered in men receiving treatment for hypogonadism or regimens for hormonal contraception.

Effects of androgen replacement on metabolism and physical performances in male hypogonadism

Hypogonadism in men is associated with decreased physical performance. This phenomenon depends on significantly measurable adverse traits in body composition, namely increased body fat content and reduced muscle mass. Physical abilities in hypogonadal men are further hampered by lower oxygen supply due to decreased hemoglobin concentrations and by poor glucose utilization. In addition, dysthymia and lack of necessary aggressiveness contribute to further deterioration of physical features. T substitution can improve lipid and insulin metabolism, resuiting in changes of body composition, such as decreasing fat depots. Growth of muscle fibers can also be observed. Stabilization of the musculo-skeletal system by increased bone density will further contribute to increased physical fitness, reflected by increased strength and endurance. Treatment outcome is strongly influenced by age and training. The issues reviewed strongly support T treatment of hypogonadal men accompanied by regular monitoring.

Effects of developmental and adult androgens on male abdominal adiposity

We present results from 42 gay men who completed a survey including self-measurement of waist circumference, height, and weight, in addition to providing saliva samples for the assay of testosterone, and a photocopy of the right hand for the measure of second-to-fourth digit length ratio (2D:4D), proposed as a means of approximating androgenic effects during development. The analyses were conducted as a test of the recent hypothesis, proposed by Abbott et al. ([2002] J Endocrinol 174:1-5), that high prenatal androgen exposure causes greater deposition of fat on the abdomen relative to other depots. We found support for this hypothesis in men, albeit in a limited sample and with self-reported and self-collected data.

Regulation of body composition by androgens

Human body can be viewed simplistically as being composed of fat-free and fat mass. With more sophisticated techniques, body composition can be broken down into fat mass, skeletal muscle mass, nonmuscle lean mass, visceral mass and bone mineral content. Similarly, it is possible to obtain estimates of total body water and intracellular and extracellular water contents. Regardless of the model of body composition assessment, it is evident that androgens are important determinants of body composition; there is no body compartment that is not directly or indirectly affected by androgens. The effects of androgens on skeletal muscle mass have received the greatest attention in recent literature; however, growing body of evidence suggests that androgens also regulate fat mass, bone mineral content, nonmuscle soft tissues and body water.

Androgen effects on body composition

Androgens are known to have a role in the body fat, muscle size, muscle performance and physical function differences seen between hypogonadal and eugonadal men. The results of investigations into effects of testosterone on body composition, fat metabolism and muscle anabolism are reviewed here. Testosterone dose-response relationships are presented in studies of the effects of physiologic and supraphysiologic doses with and without exercise in young hypogonadal men, older men with low testosterone levels and in chronic illness states.

Androgen therapy improves muscle mass and strength but not muscle quality: results from two studies

The relationship of strength to muscle area was used to assess change in muscle quality after anabolic interventions. Study 1: asymptomatic human immunodeficiency virus-positive men (39 +/- 9 yr) were randomized to nandrolone (600 mg/wk) +/- resistance training (RT). Study 2: older healthy men (72 +/- 5 yr) were randomized to oxandrolone (20 mg/day) or placebo. Maximum voluntary strength was determined by the 1-repetition maximum (1-RM) method for leg press, flexion and extension, and cross-sectional area of leg muscles by MRI. From study week 0 to study week 12, muscle quality was unchanged with nandrolone, oxandrolone, or oxandrolone placebo, respectively, for total thigh muscles (1.23 +/- 0.012 vs. 1.27 +/- 0.29 kg/cm2; 9.0 +/- 1.1 vs. 8.9 +/- 1.2 N/cm2; 8.9 +/- 1.2 vs. 8.9 +/- 1.9 N/cm2) and hamstrings (0.41 +/- 0.08 vs. 0.43 +/- 0.07 kg/cm2; 0.90 +/- 0.14 vs. 0.95 +/- 0.016 N/cm2; 0.94 +/- 0.23 vs. 0.93 +/- 0.21 N/cm2). Lower-extremity 1-RM strength increased several times greater with RT+nandrolone (51-63% increases) than with nandrolone alone (4.7-16%), despite similar increases in muscle area; therefore, muscle quality increased from 1.13 +/- 0.17 to 1.51 +/- 0.18 kg/cm2 (+36 +/- 19%; P < 0.001) for total thigh muscle, 0.37 +/- 0.10 to 0.53 +/- 0.08 kg/cm2 (+49 +/- 39%; P < 0.001) for hamstrings, and 0.73 +/- 0.19 to 1.07 +/- 0.16 kg/cm2 (+55 +/- 36%; P < 0.001) for quadriceps. Thus androgen therapy alone did not improve muscle quality, but the addition of RT to nandrolone produced substantive improvements.

Testosterone-induced muscle hypertrophy is associated with an increase in satellite cell number in healthy, young men

Testosterone (T) supplementation in men induces muscle fiber hypertrophy. We hypothesized that T-induced increase in muscle fiber size is associated with a dose-dependent increase in satellite cell number. We quantitated satellite cell and myonuclear number by using direct counting and spatial orientation methods in biopsies of vastus lateralis obtained at baseline and after 20 wk of treatment with a gonadotropin-releasing hormone agonist and a 125-, 300-, or 600-mg weekly dose of T enanthate. T administration was associated with a significant increase in myonuclear number in men receiving 300- and 600-mg doses. The posttreatment percent satellite cell number, obtained by direct counting, differed significantly among the three groups (ANCOVA P < 0.000001); the mean posttreatment values (5.0 and 15.0%) in men treated with 300- and 600-mg doses were greater than baseline (2.5 and 2.5%, respectively, P < 0.05 vs. baseline). The absolute satellite cell number measured by spatial orientation at 20 wk (1.5 and 4.0/mm) was significantly greater than baseline (0.3 and 0.6/mm) in men receiving the 300- and 600-mg doses (P < 0.05). The change in percent satellite cell number correlated with changes in total (r = 0.548) and free T concentrations (r = 0.468). Satellite cell and mitochondrial areas were significantly higher and the nuclear-to-cytoplasmic ratio lower after treatment with 300- and 600-mg doses. We conclude that T-induced muscle fiber hypertrophy is associated with an increase in satellite cell number, a proportionate increase in myonuclear number, and changes in satellite cell ultrastructure.

Oral testosterone supplementation increases muscle and decreases fat mass in healthy elderly males with low-normal gonadal status

BACKGROUND

Loss of muscle mass (sarcopenia) leads to frailty in older men. The decline in testosterone over the life span may contribute to this muscle loss. We studied the ability of oral testosterone to prevent muscle loss in older men over a 12-month period.

METHODS

A standard dose (80 mg twice daily) of testosterone undecanoate or placebo was administered for 1 year to 76 healthy men aged 60 years or older. All men had a free testosterone index 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. Measurements of body composition, muscle strength, hormones, and safety parameters were obtained at 0, 6, and 12 months.

RESULTS

Lean body mass increased (p =.0001) and fat mass decreased (p =.02) in the testosterone as compared with the placebo-treated group. There were no significant effects on muscle strength. There was a significant increase in hematocrit (0.02%) in the testosterone-treated group (p =.03). Plasma triglycerides, total cholesterol, and low-density lipoprotein cholesterol levels were similar in both groups, but there was a decrease in high-density lipoprotein cholesterol (-0.1 mmol/L) at 12 months in the testosterone group as compared to the placebo group (p = 0.026). There were no differences in prostate-specific antigen or systolic or diastolic blood pressure between the groups.

CONCLUSION

Oral testosterone administration to older relatively hypogonadal men results in an increase in muscle mass and a decrease in body fat.

Testosterone administration to men increases hepatic lipase activity and decreases HDL and LDL size in 3 wk

Testosterone administration to men is known to decrease high-density lipoprotein cholesterol (HDL-C) and the subclasses HDL(2) and HDL(3). It also might increase the number of small, dense, low-density lipoprotein cholesterol (LDL-C) particles in hypogonadal men. The decrease in HDL-C and in LDL-C size is potentially mediated by hepatic lipase activity, which hydrolyzes lipoprotein phospholipids and triacylglycerol. To determine how HDL-C and LDL-C particles are affected by testosterone administration to eugonadal men, testosterone was administered as a supraphysiological dose (600 mg/wk) for 3 wk to elderly, obese, eugonadal men before elective hip or knee surgery, and lipids were measured by routine methods and by density gradient ultracentrifugation. Hepatic lipase activity increased >60% above baseline levels, and HDL-C, HDL(2), and HDL(3) significantly declined in 3 wk. In addition, the LDL-C peak particle density and the amount of LDL-C significantly increased. Testosterone is therefore a potent stimulator of hepatic lipase activity, decreasing HDL-C, HDL(2), and HDL(3) as well as increasing LDL particle density changes, all associated with increased cardiovascular risk.

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.

Energetics and reproductive effort

Natural selection favors the optimal allocation of energy and other limiting resources to reproduction. Human reproductive physiology displays characteristic patterns that can be viewed as mechanisms that help optimize reproductive effort in the face of environmental energetic constraints. Female ovarian function is particularly sensitive to energy balance and energy flux, resulting in a synchronization of conception with favorable energetic conditions. Reproductive effort during gestation is highly buffered from environmental energetic constraints, but the duration of gestation and final birthweight are both very sensitive to maternal energy availability. Milk production during lactation is relatively buffered from maternal energetic constraints as well, but the duration of lactational amenorrhea is sensitive to the relative metabolic load of lactation. Male gamete production is very insensitive to energetic constraints, but variation in testosterone production in response to both age and longer-lasting energetic conditions contributes to the modulation of somatic and behavioral aspects of male reproductive effort, aspects that are more energetically costly for a male. There is also new evidence that testosterone may also help to modulate the trade-off between male parenting and mating effort.

Development of models to predict anabolic response to testosterone administration in healthy young men

Considerable heterogeneity exists in the anabolic response to androgen administration; however, the factors that contribute to variation in an individual's anabolic response to androgens remain unknown. We investigated whether testosterone dose and/or any combination of baseline variables, including concentrations of hormones, age, body composition, muscle function, and morphometry or polymorphisms in androgen receptor could explain the variability in anabolic response to testosterone. Fifty-four young men were treated with a long-acting gonadotropin-releasing hormone (GnRH) agonist and one of five doses (25, 50, 125, 300, or 600 mg/wk) of testosterone enanthate (TE) for 20 wk. Anabolic response was defined as a change in whole body fat-free mass (FFM) by dual-energy X-ray absorptiometry (DEXA), appendicular FFM (by DEXA), and thigh muscle volume (by magnetic resonance imaging) during TE treatment. We used univariate and multivariate analysis to identify the subset of baseline measures that best explained the variability in anabolic response to testosterone supplementation. The three-variable model of TE dose, age, and baseline prostate-specific antigen (PSA) level explained 67% of the variance in change in whole body FFM. Change in appendicular FFM was best explained (64% of the variance) by the linear combination of TE dose, baseline PSA, and leg press strength, whereas TE dose, log of the ratio of luteinizing hormone to testosterone concentration, and age explained 66% of the variation in change in thigh muscle volume. The models were further validated by using Ridge analysis and cross-validation in data subsets. Only the model using testosterone dose, age, and PSA was a consistent predictor of change in FFM in subset analyses. The length of CAG tract was only a weak predictor of change in thigh muscle volume and lean body mass. Hence, the anabolic response of healthy, young men to exogenous testosterone administration can largely be predicted by the testosterone dose.

Androgens and coronary artery disease

A significant and independent association between endogenous testosterone (T) levels and coronary events in men and women has not been confirmed in large prospective studies, although cross-sectional data have suggested coronary heart disease can be associated with low T in men. Hypoandrogenemia in men and hyperandrogenemia in women are associated with visceral obesity; insulin resistance; low high-density lipoprotein (HDL) cholesterol (HDL-C); and elevated triglycerides, low-density lipoprotein cholesterol, and plasminogen activator type 1. These gender differences and confounders render the precise role of endogenous T in atherosclerosis unclear. Observational studies do not support the hypothesis that dehydroepiandrosterone sulfate deficiency is a risk factor for coronary artery disease. The effects of exogenous T on cardiovascular mortality or morbidity have not been extensively investigated in prospective controlled studies; preliminary data suggest there may be short-term improvements in electrocardiographic changes in men with coronary artery disease. In the majority of animal experiments, exogenous T exerts either neutral or beneficial effects on the development of atherosclerosis. Exogenous androgens induce both apparently beneficial and deleterious effects on cardiovascular risk factors by decreasing serum levels of HDL-C, plasminogen activator type 1 (apparently deleterious), lipoprotein (a), fibrinogen, insulin, leptin, and visceral fat mass (apparently beneficial) in men as well as women. However, androgen-induced declines in circulating HDL-C should not automatically be assumed to be proatherogenic, because these declines may instead reflect accelerated reverse cholesterol transport. Supraphysiological concentrations of T stimulate vasorelaxation; but at physiological concentrations, beneficial, neutral, and detrimental effects on vascular reactivity have been observed. T exerts proatherogenic effects on macrophage function by facilitating the uptake of modified lipoproteins and an antiatherogenic effect by stimulating efflux of cellular cholesterol to HDL. In conclusion, the inconsistent data, which can only be partly explained by differences in dose and source of androgens, militate against a meaningful assessment of the net effect of T on atherosclerosis. Based on current evidence, the therapeutic use of T in men need not be restricted by concerns regarding cardiovascular side effects. Available data also do not justify the uncontrolled use of T or dehydroepiandrosterone for the prevention or treatment of coronary heart disease.

Effects of an oral androgen on muscle and metabolism in older, community-dwelling men

To determine whether oxymetholone increases lean body mass (LBM) and skeletal muscle strength in older persons, 31 men 65-80 yr of age were randomized to placebo (group 1) or 50 mg (group 2) or 100 mg (group 3) daily for 12 wk. For the three groups, total LBM increased by 0.0 +/- 0.6, 3.3 +/- 1.2 (P < 0.001), and 4.2 +/- 2.4 kg (P < 0.001), respectively. Trunk fat decreased by 0.2 +/- 0.4, 1.7 +/- 1.0 (P = 0.018), and 2.2 +/- 0.9 kg (P = 0.005) in groups 1, 2, and 3, respectively. Relative increases in 1-repetition maximum (1-RM) strength for biaxial chest press of 8.2 +/- 9.2 and 13.9 +/- 8.1% in the two active treatment groups were significantly different from the change (-0.8 +/- 4.3%) for the placebo group (P < 0.03). For lat pull-down, 1-RM changed by -0.6 +/- 8.3, 8.8 +/- 15.1, and 18.4 +/- 21.0% for the groups, respectively (1-way ANOVA, P = 0.019). The pattern of changes among the groups for LBM and upper-body strength suggested that changes might be related to dose. Alanine aminotransferase increased by 72 +/- 67 U/l in group 3 (P < 0.001), and HDL-cholesterol decreased by -19 +/- 9 and -23 +/- 18 mg/dl in groups 2 and 3, respectively (P = 0.04 and P = 0.008). Thus oxymetholone improved LBM and maximal voluntary muscle strength and decreased fat mass in older men.

Male contraception

The provision of safe, effective contraception has been revolutionized in the past 40 yr following the development of synthetic steroids and the demonstration that administration of combinations of sex steroids can be used to suppress ovulation and, subsequently, other reproductive functions. This review addresses the current standing of male contraception, long the poor relation in family planning but currently enjoying a resurgence in both scientific and political interest as it is recognized that men have a larger role to play in the regulation of fertility, whether seen in geopolitical or individual terms. Condoms and vasectomy continue to be popular at particular phases of the reproductive lifespan and in certain cultures. Although not perfect contraceptives, condoms have the additional advantage of offering protection from sexually transmitted infection. The hormonal approach may have acquired the critical mass needed to make the transition from academic research to pharmaceutical development. Greatly increased understanding of male reproductive function, partly stimulated by interest in ageing and the potential benefits of androgen replacement, is opening up other avenues for investigation taking advantage of nonhormonal regulatory pathways specific to spermatogenesis and the reproductive tract.

Metabolic effects of nandrolone decanoate and resistance training in men with HIV

Thirty human immunodeficiency virus (HIV)-infected men were randomized to a high dose of nandrolone decanoate weekly (group 1) or nandrolone plus resistance training (group 2) for 12 wk. For the two groups, nandrolone had no significant effects on total cholesterol, LDL cholesterol, LDL phenotype, or fasting triglycerides, although triglycerides decreased by 66 +/- 124 mg/dl for the entire population (P = 0.01). Group 2 subjects had a favorable increase of 5.2 +/- 7.7A in LDL particle size (P = 0.03), whereas there was no change in group 1. Lipoprotein(a) decreased by 7.3 +/- 6.8 mg/dl for group 1 (P = 0.002) and by 6.9 +/- 8.1 for group 2 (P = 0.013). However, HDL cholesterol decreased by 8.7 +/- 7.4 mg/dl for group 1 (P < 0.001) and by 10.6 +/- 5.9 for group 2 (P < 0.001). Percentages of HDL(2b) (9.7-12 nm) and HDL(2a) (8.8-9.7 nm) subfractions decreased similarly for the two groups, whereas HDL(3a) (8.2-8.8 nm) and HDL(3b) (7.8-8.2 nm) increased in the groups during study therapy (P < or = 0.02 for all comparisons). There was no evidence of a decreased insulin sensitivity in either group, whereas fasting glucose, fasting insulin, and homeostasis model assessment improved in group 2 (P < 0.05). These metabolic effects were favorable (other than for HDL), but changes were generally transient (except for HDL in group 2), with measurements returning to baseline 2 mo after the interventions were completed.

Investigation of a novel preparation of testosterone decanoate in men: pharmacokinetics and spermatogenic suppression with etonogestrel implants

We have investigated the pharmacokinetics and effects on the male reproductive axis of a novel preparation of testosterone decanoate (TD) with a progestogen implant. Twenty healthy Chinese men were administered TD (400 mg intramuscular 4 weekly) with two subcutaneous (SC) etonogestrel implants. Trough testosterone concentrations rose with repeated administration. Peak concentrations 1 week after the fourth injection were 31 +/- 2 nmol/liter. Both LH and FSH were rapidly suppressed and continued to fall during treatment. Spermatogenesis was also suppressed, to <or=1 x 10(6)/mL in all men with 16 (80%) azoospermic at 12 weeks. Treatment was associated with an increase in weight, and also increases in hemoglobin concentration (9%) and hematocrit (15%). No subjects withdrew from the study, although the study was terminated after subjects had completed 12 to 18 weeks as some men were found to have elevated liver enzyme tests. These data demonstrate that the pharmacokinetics of TD are improved compared to previous injectable testosterone preparations, although peak testosterone concentrations rise briefly into the supraphysiological range. The speed and degree of spermatogenic suppression suggest that this combination has promise as an effective male contraceptive.

Testosterone-induced increase in muscle size in healthy young men is associated with muscle fiber hypertrophy

Administration of replacement doses of testosterone to healthy hypogonadal men and supraphysiological doses to eugonadal men increases muscle size. To determine whether testosterone-induced increase in muscle size is due to muscle fiber hypertrophy, 61 healthy men, 18-35 yr of age, received monthly injections of a long-acting gonadotropin-releasing hormone (GnRH) agonist to suppress endogenous testosterone secretion and weekly injections of 25, 50, 125, 300, or 600 mg testosterone enanthate (TE) for 20 wk. Thigh muscle volume was measured by magnetic resonance imaging (MRI) scan, and muscle biopsies were obtained from vastus lateralis muscle in 39 men before and after 20 wk of combined treatment with GnRH agonist and testosterone. Administration of GnRH agonist plus TE resulted in mean nadir testosterone concentrations of 234, 289, 695, 1,344, and 2,435 ng/dl at the 25-, 50-, 125-, 300-, and 600-mg doses, respectively. Graded doses of testosterone administration were associated with testosterone dose and concentration-dependent increase in muscle volume measured by MRI (changes in vastus lateralis volume, -4, +7, +15, +32, and +48 ml at 25-, 50-, 125-, 300-, and 600-mg doses, respectively). Changes in cross-sectional areas of both type I and II fibers were dependent on testosterone dose and significantly correlated with total (r = 0.35, and 0.44, P < 0.0001 for type I and II fibers, respectively) and free (r = 0.34 and 0.35, P < 0.005) testosterone concentrations during treatment. The men receiving 300 and 600 mg of TE weekly experienced significant increases from baseline in areas of type I (baseline vs. 20 wk, 3,176 +/- 186 vs. 4,201 +/- 252 microm(2), P < 0.05 at 300-mg dose, and 3,347 +/- 253 vs. 4,984 +/- 374 microm(2), P = 0.006 at 600-mg dose) muscle fibers; the men in the 600-mg group also had significant increments in cross-sectional area of type II (4,060 +/- 401 vs. 5,526 +/- 544 microm(2), P = 0.03) fibers. The relative proportions of type I and type II fibers did not change significantly after treatment in any group. The myonuclear number per fiber increased significantly in men receiving the 300- and 600-mg doses of TE and was significantly correlated with testosterone concentration and muscle fiber cross-sectional area. In conclusion, the increases in muscle volume in healthy eugonadal men treated with graded doses of testosterone are associated with concentration-dependent increases in cross-sectional areas of both type I and type II muscle fibers and myonuclear number. We conclude that the testosterone induced increase in muscle volume is due to muscle fiber hypertrophy.