Studies of the human testis. XVIII. Simultaneous measurement of nine intratesticular steroids: evidence for reduced mitochondrial function in testis of elderly men

Ageing male (part I): Pathophysiology and diagnosis of functional hypogonadism

This narrative review summarizes key points of the pathogenesis and diagnosis of the ageing-related decline of testosterone (T) in men. The condition is commonly termed late-onset hypogonadism (LOH), but because it is more often caused by other factors than chronological ageing (obesity and other comorbidities), a more appropriate term is functional hypogonadism (FH). Unlike the classical organic hypogonadism, no anatomical or genetic aberrations are found in FH, and the suppression of T is milder. Moreover, FH can be reversible if the underlying cause (e.g. obesity, chronic disease) is removed/treated. Low serum total T in connection with more specific hypogonadism-associated symptoms (primarily sexual) form the basis of the diagnosis of FH. When T concentrations are borderline, the accuracy of diagnosis can be improved by assessment of free or calculated free T, especially when suppressed SHBG levels (usually related to obesity) are likely. Current data indicate that FH (low T and sexual symptoms) is not a common condition, and it is detectable in about 2% of community-dwelling men aged 40-80 years.

Determination of Intraprostatic and Intratesticular Androgens

Androgens represent the main hormones responsible for maintaining hormonal balance and function in the prostate and testis. As they are involved in prostate and testicular carcinogenesis, more detailed information of their active concentration at the site of action is required. Since the introduction of the term intracrinology as the local formation of active steroid hormones from inactive precursors of the adrenal gland, mainly dehydroepiandrosterone (DHEA) and DHEA-S, it is evident that blood circulating levels of sex steroid hormones need not reflect their actual concentrations in the tissue. Here, we review and critically evaluate available methods for the analysis of human intraprostatic and intratesticular steroid concentrations. Since analytical approaches have much in common in both tissues, we discuss them together. Preanalytical steps, including various techniques for separation of the analytes, are compared, followed by the end-point measurement. Advantages and disadvantages of chromatography-mass spectrometry (LC-MS, GC-MS), immunoanalytical methods (IA), and hybrid (LC-IA) are discussed. Finally, the clinical information value of the determined steroid hormones is evaluated concerning differentiating between patients with cancer or benign hyperplasia and between patients with different degrees of infertility. Adrenal-derived 11-oxygenated androgens are mentioned as perspective prognostic markers for these purposes.

Comparative Study of the Steroidogenic Effects of Human Chorionic Gonadotropin and Thieno[2,3-D]pyrimidine-Based Allosteric Agonist of Luteinizing Hormone Receptor in Young Adult, Aging and Diabetic Male Rats

Low-molecular-weight agonists of luteinizing hormone (LH)/human chorionic gonadotropin (hCG) receptor (LHCGR), which interact with LHCGR transmembrane allosteric site and, in comparison with gonadotropins, more selectively activate intracellular effectors, are currently being developed. Meanwhile, their effects on testicular steroidogenesis have not been studied. The purpose of this work is to perform a comparative study of the effects of 5-amino-N-tert-butyl-4-(3-(1-methylpyrazole-4-carboxamido)phenyl)-2-(methylthio)thieno[2,3-d] pyrimidine-6-carboxamide (TP4/2), a LHCGR allosteric agonist developed by us, and hCG on adenylyl cyclase activity in rat testicular membranes, testosterone levels, testicular steroidogenesis and spermatogenesis in young (four-month-old), aging (18-month-old) and diabetic male Wistar rats. Type 1 diabetes was caused by a single streptozotocin (50 mg/kg) injection. TP4/2 (20 mg/kg/day) and hCG (20 IU/rat/day) were administered for 5 days. TP4/2 was less effective in adenylyl cyclase stimulation and ability to activate steroidogenesis when administered once into rats. On the 3rd–5th day, TP4/2 and hCG steroidogenic effects in young adult, aging and diabetic rats were comparable. Unlike hCG, TP4/2 did not inhibit LHCGR gene expression and did not hyperstimulate the testicular steroidogenesis system, moderately increasing steroidogenic proteins gene expression and testosterone production. In aging and diabetic testes, TP4/2 improved spermatogenesis. Thus, during five-day administration, TP4/2 steadily stimulates testicular steroidogenesis, and can be used to prevent androgen deficiency in aging and diabetes.

Testicular Aging: An Overview of Ultrastructural, Cellular, and Molecular Alterations

The trend in parenthood at an older age is increasing for both men and women in developed countries, raising concerns about the reproductive ability, and the consequences for the offspring's health. While reproductive activity in women stops with menopause, a complete cessation of the reproductive potential does not occur in men. Although several studies have been published on the effects of aging on semen parameters and spermatozoa DNA integrity, literature on impact of aging on the testis, particularly cellular, and molecular alterations, has been, so far, limited and controversial. This work discusses the current knowledge on testicular aging in humans and other mammals, covering topics from tissue ultrastructure, to cellular and molecular alterations. Aging affects male reproductive function at multiple levels, from sperm production and quality, to the morphology and histology of the male reproductive system. The morphological and functional changes that occur in the testes result in variations in the levels of many hormones, changes in molecules involved in mitochondrial function, receptors, and signaling proteins. Despite knowing that these age-related alterations occur, their real impact on male fertility and reproductive health are still far from being fully understood, highlighting that research in the field is crucial.

Aging and the Male Reproductive System

This narrative review presents an overview of current knowledge on fertility and reproductive hormone changes in aging men, the factors driving and modulating these changes, their clinical consequences, and the benefits and risks of testosterone (T) therapy. Aging is accompanied by moderate decline of gamete quality and fertility. Population mean levels show a mild total T decline, an SHBG increase, a steeper free T decline, and a moderate LH increase with important contribution of comorbidities (e.g., obesity) to these changes. Sexual symptoms and lower hematocrit are associated with low T and are partly responsive to T therapy. The relationship of serum T with body composition and metabolic health is bidirectional; limited beneficial effects of T therapy on body composition have only marginal effects on metabolic health and physical function. Skeletal changes are associated primarily with estradiol and SHBG. Cognitive decline is not consistently linked to low T and is not improved by T therapy. Although limited evidence links moderate androgen decline with depressive symptoms, T therapy has small beneficial effects on mood, depressive symptoms, and vitality in elderly patients with low T. Suboptimal T (and/or DHT) has been associated with increased risk of stroke, but not of ischemic heart disease, whereas an association with mortality probably reflects that low T is a marker of poor health. Globally, neither severity of clinical consequences attributable to low T nor the nature and magnitude of beneficial treatment effects justify the concept of some broadly applied "T replacement therapy" in older men with low T. Moreover, long-term safety of T therapy is not established.

The endocrine dyscrasia that accompanies menopause and andropause induces aberrant cell cycle signaling that triggers re-entry of post-mitotic neurons into the cell cycle, neurodysfunction, neurodegeneration and cognitive disease

This article is part of a Special Issue "SBN 2014". Sex hormones are physiological factors that promote neurogenesis during embryonic and fetal development. During childhood and adulthood these hormones support the maintenance of brain structure and function via neurogenesis and the formation of dendritic spines, axons and synapses required for the capture, processing and retrieval of information (memories). Not surprisingly, changes in these reproductive hormones that occur with menopause and during andropause are strongly correlated with neurodegeneration and cognitive decline. In this connection, much evidence now indicates that Alzheimer's disease (AD) involves aberrant re-entry of post-mitotic neurons into the cell cycle. Cell cycle abnormalities appear very early in the disease, prior to the appearance of plaques and tangles, and explain the biochemical, neuropathological and cognitive changes observed with disease progression. Intriguingly, a recent animal study has demonstrated that induction of adult neurogenesis results in the loss of previously encoded memories while decreasing neurogenesis after memory formation during infancy mitigated forgetting. Here we review the biochemical, epidemiological and clinical evidence that alterations in sex hormone signaling associated with menopause and andropause drive the aberrant re-entry of post-mitotic neurons into an abortive cell cycle that leads to neurite retraction, neuron dysfunction and neuron death. When the reproductive axis is in balance, gonadotropins such as luteinizing hormone (LH), and its fetal homolog, human chorionic gonadotropin (hCG), promote pluripotent human and totipotent murine embryonic stem cell and neuron proliferation. However, strong evidence supports menopausal/andropausal elevations in the LH:sex steroid ratio as driving aberrant mitotic events. These include the upregulation of tumor necrosis factor; amyloid-β precursor protein processing towards the production of mitogenic Aβ; and the activation of Cdk5, a key regulator of cell cycle progression and tau phosphorylation (a cardinal feature of both neurogenesis and neurodegeneration). Cognitive and biochemical studies confirm the negative consequences of a high LH:sex steroid ratio on dendritic spine density and human cognitive performance. Prospective epidemiological and clinical evidence in humans supports the premise that rebalancing the ratio of circulating gonadotropins:sex steroids reduces the incidence of AD. Together, these data support endocrine dyscrasia and the subsequent loss of cell cycle control as an important etiological event in the development of neurodegenerative diseases including AD, stroke and Parkinson's disease.

Mitochondrial and sex steroid hormone crosstalk during aging

Decline in circulating sex steroid hormones accompanies several age-associated pathologies which may influence human healthspan. Mitochondria play important roles in biosynthesis of sex steroid hormones, and these hormones can also regulate mitochondrial function. Understanding the cross talk between mitochondria and sex steroid hormones may provide insights into the pathologies associated with aging. The aim of this review is to summarize the current knowledge regarding the interplay between mitochondria and sex steroid hormones during the aging process. The review describes the effect of mitochondria on sex steroid hormone production in the gonads, and then enumerates the contribution of sex steroid hormones on mitochondrial function in hormone responsive cells. Decline in sex steroid hormones and accumulation of mitochondrial damage may create a positive feedback loop that contributes to the progressive degeneration in tissue function during aging. The review further speculates whether regulation between mitochondrial function and sex steroid hormone action can potentially influence healthspan.

Physiologic role and regulation of intratesticular sex steroids

PURPOSE OF REVIEW

To summarize recent advances in our understanding of the role and regulation of intratesticular androgens, and their metabolites, in human spermatogenesis.

RECENT FINDINGS

Over the last few years, a number of studies have been published examining intratesticular sex steroid concentrations in normal men following gonadotropin manipulation and in the setting of impaired fertility. Advances in the field have been facilitated by the availability of more sensitive and specific assays for intratesticular sex steroid quantification. High levels of intratesticular androgens are required for normal spermatogenesis in men. However, the quantitative relationship between intratesticular testosterone concentrations and male fertility is not fully understood. In the setting of impaired spermatogenesis, intratesticular metabolites of testosterone may play a role in initiating or maintaining fertility.

SUMMARY

Advances in the precision of androgen measurements and recent studies examining intratesticular responses to hormonal manipulation have advanced our understanding of the testicular microenvironment. These advances have set the stage for future studies in this area which will be important for moving forward male hormonal contraceptive development and furthering our understanding of male reproductive pathology. Whether 'gonadotropin-independent' intratesticular androgen synthesis plays a role in human spermatogenesis will likely be a focus of investigation in the coming years.

The effect of gonadotropin withdrawal and stimulation with human chorionic gonadotropin on intratesticular androstenedione and DHEA in normal men

INTRODUCTION

Concentrations of intratesticular (IT) testosterone (T) are known to be 100-200 times those of serum T; however, the IT concentrations of T's precursors, their testicular to serum gradients, gonadotropin dependence, and response to stimulation with human chorionic gonadotropin (hCG) have not been studied in detail. We hypothesized that serum and IT androstenedione (ADD) and IT dehydroepiandrosterone (DHEA) would be significantly suppressed by the administration of a GnRH antagonist and increased when stimulated by hCG, without a similar suppression of serum DHEA.

METHODS

We suppressed gonadotropins in 23 normal men with the GnRH antagonist acyline and randomly assigned them to one of four doses of hCG, 0, 15, 60, or 125 IU sc every other day for 10 d. Blood and IT fluid for the measurement of serum and IT hormones were obtained at baseline and after 10 d of treatment.

RESULTS

Baseline IT ADD [median (25th, 75th percentile)] was 629 (308, 860) nmol/liter, and IT DHEA was 564 (411, 879) nmol/liter, which were 175 and 27 times higher than their respective serum concentrations. IT ADD and IT DHEA were suppressed by 98 and 82%, respectively, by acyline and significantly increased with hCG administration. Likewise, serum ADD was suppressed by 50%, but serum DHEA was unchanged.

DISCUSSION

ADD and DHEA are highly concentrated within the human testes compared with serum. Serum and IT ADD and IT DHEA are markedly suppressed with GnRH administration and stimulated by hCG, but serum DHEA is not, suggesting that most circulating DHEA is not of testicular origin.

Aging of the human ovary and testis

Aging is associated with structural and functional alterations in all organs of the human body. The aging of gonads represents in this respect a special case, because these organs are not functional for the whole lifespan of an individual and their normal function is not indispensable for functions of the rest of the body. Ovarian function lasts for the reproductive life of a woman, i.e., from menarche until menopause. The testicular endocrine function, in contrast, begins already in utero, is interrupted between neonatal life and puberty, and continues thereafter along with spermatogenesis, with only slight decline, until old age. The aging processes of the ovary and testis are therefore very different. We describe in this review the structural and functional alterations in the human ovary and testis upon aging. Special emphasis will be given to clinically significant alterations, which in women concern the causes and consequences of the individual variability of fertility during the latter part of the reproductive age. The clinically important aspect of testicular aging entails the decline of androgen production in aging men.

The ageing male reproductive tract

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

Molecular aspects of declining sperm motility in older men

OBJECTIVE

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

DESIGN

Retrospective and prospective study.

SETTING

University-based andrology unit.

PATIENT(S)

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

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

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

RESULT(S)

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

CONCLUSION(S)

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

Human 17beta-hydroxysteroid dehydrogenases types 1, 2, and 3 catalyze bi-directional equilibrium reactions, rather than unidirectional metabolism, in HEK-293 cells

Human 17beta-hydroxysteroid dehydrogenases (17betaHSDs) catalyze the interconversion of weak and potent androgen and estrogen pairs. Although the reactions using purified enzymes can be driven in either direction, these enzymes appear to function unidirectionally in intact cells: only reductive reactions for 17betaHSD1 and 17beta HSD3 and only oxidative reactions for 17betaHSD2. We show that, after exhaustive incubations with either 17beta-hydroxy- or 17-ketosteroid, the medium for HEK-293 cells expressing 17betaHSD1 or 17betaHSD3 contains a 92:8 ratio of reduced:oxidized steroid. Similarly, 17betaHSD2 yields a >95:5 ratio of oxidized:reduced steroids for both androgens and estrogens. Dual-isotope kinetic measurements show that the rates of the forward and reverse reactions are identical at these functional equilibrium states in intact cells for all three 17betaHSD isoforms, and these rates are much faster than those estimated from single-isotope flux studies. Mutation L36D converts 17betaHSD1 to an oxidative enzyme in intact cells, reversing the equilibrium distribution of estradiol:estrone to 5:95; however, the rates of the forward and reverse reactions at equilibrium are equal and comparable to those of the wild-type enzymes. The co-expression of 17betaHSD2 paradoxically increases the potency of estrone in transactivation assays, demonstrating the physiological relevance of "backwards" metabolism to estradiol. We conclude that 17betaHSD types 1, 2, and 3 catalyze both oxidative and reductive reactions in HEK-293 cells at intrinsic rates that are much faster than those estimated from single-isotope studies. These 17betaHSD isoforms do not drive steroid flux in one direction but rather may achieve functional equilibria in intact cells, reflecting thermodynamically driven steroid distributions.

Current controversies in testosterone testing: aging and obesity

The interpretation of the total serum testosterone concentration is problematic because it is related directly to the serum SHBG concentration.Frequently, an estimate of the serum free testosterone concentration is obtained to better assess the clinical status of the patient. We reviewed five methods for the determination of free testosterone or a surrogate test/index and the problems with these methods. The calculated free testosterone or BAT (highly positively correlated) are recommended as the preferred tests to assess biologically-active testosterone, although interlaboratory values may differ because standards are not available. The controversies in evaluating gonadal function are illustrated by the andropause (elevated SHBG) and obese men (decreased SHBG).

Cell biology of Leydig cells in the testis

This article reviews results on differentiation, structure, and regulation of Leydig cells in the testes of rodents and men. Two different populations-fetal and adult Leydig cells-can be recognized in rodents. The cells in these two populations are different in ultrastructure, life span, capacity for androgen synthesis, and mechanisms of regulation. A brief survey on the origin, ontogenesis, characterization of precursors, ultrastructure, and functional markers of fetal and adult Leydig cells is presented, followed by an analysis of genes in Leydig cells and the role of luteinizing hormone and its receptor, steroidogenic acute regulatory protein, hydroxysteroid dehydrogenases, androgen and its receptor, anti-Müllerian hormone, estrogens, and thyroid hormones. Various growth factors modulate Leydig cell differentiation, regeneration, and steroidogenic capacity, for example, interleukin 1alpha, transforming growth factor beta, inhibin, insulin-like growth factors I and II, vascular endothelial growth factor, and relaxin-like growth factor. Retinol and retinoic acid increase basal testosterone secretion in adult Leydig cells, but decrease it in fetal Leydig cells. Resident macrophages in the interstitial tissue of the testis are important for differentiation and function of Leydig cells. Apoptosis of Leydig cells is involved in the regulation of Leydig cell number and can be induced by cytotoxins. Characteristics of aging Leydig cells in rodents seem to be species specific. 11beta-hydroxysteroid dehydrogenase protects testosterone synthesis in the Leydig cells of stressed rats. Last, the following aspects of human Leydig cells are briefly described: origin, differentiation, triphasic development, aging changes, pathological changes, and gene mutations leading to infertility.

Construction and field validation of a self-administered screener for testosterone deficiency (hypogonadism) in ageing men

To design a self-administered screening questionnaire to inform men about their risk for testosterone deficiency. The screener was developed in two phases. First was a construction phase in which relevant risk factors and a scoring algorithm were defined from multiple logistic regression analyses of survey data. In the second phase, the screener's accuracy (based on sensitivity, specificity, and Receiver Operating Characteristic (ROC) curves) was tested using patients from a primary care clinic. All subjects provided blood samples for endocrine testing. Survey data from 1660 men aged 40-79 years participating in the Massachusetts Male Ageing Study (MMAS) were analysed in the first phase. The clinic sample consisted of 304 men aged 40-79 years presenting at a large Massachusetts primary health care clinic for routine check-ups or minor medical problems. The primary outcome was testosterone deficiency, defined as serum total testosterone below 12.1 nmol/l. Self-reported variables considered as potential risk factors included age, obesity, chronic diseases, health behaviour, the Jackson dominance scale, and symptoms of stress. The prevalence of testosterone deficiency was 20.4% in the MMAS and 42.1% in the clinic sample. An eight-item screener was developed based on age, body mass index, diabetes, asthma, headaches, sleep patterns, dominance preferences, and smoking status. The screener performed significantly better than chance in identifying men with low testosterone levels; the area under the ROC curve was 0.66 in the MMAS sample and 0.67 in the clinic sample. The self-scored screener developed in this study reliably detects men at risk of hypogonadism. The screener encourages at risk men to seek professional evaluation of their testosterone levels.

Testosterone replacement therapy in older adult men

Serum testosterone levels decline slowly with normal ageing in men and, although all men are not destined to become hypogonadal as they age, the prevalence of androgen deficiency in the older male is not insignificant. Over the past several decades, there has been an increasing interest in evaluating whether testosterone therapy (male HRT) might be beneficial for certain older men in preventing or reversing some aspects of ageing. The major androgen target organs of interest with regard to beneficial effects of male HRT include bone, muscle, adipose tissue, the cardiovascular system and the central nervous system (libido and aspects of mood). At the same time, potential adverse effects of male HRT on target organs such as the prostate continue to be evaluated. It is the purpose of this review to summarize the information to date with regard to testosterone replacement therapy in the older man and to discuss areas where more research and clinical information need to be forthcoming. Hormonal replacement therapy (HRT) for post-menopausal women has been studied and discussed for many years. The idea of male HRT, however, is a relatively recent development, with increasing interest in this area occurring only over the past two decades. Reasons for this nascent enthusiasm include burgeoning evidence that testosterone levels decline with normal male ageing (and with age-associated diseases) and an interest in preventing age-related dysfunction and prolonging quality life among an ever increasing population of older adults. The decline in testosterone with age often parallels unfavourable changes in organs upon which androgens act and the goal of male HRT would be to prevent, stabilize or even reverse some of these detrimental target-organ changes.

Male hormone replacement therapy including "andropause"

Adult onset male hypogonadism and the testosterone deficiency of the aging male often are under-recognized entities. The etiologies, presentation, and diagnosis of hypogonadism and andropause in the adult male are presented. The expected therapeutic goals, potential treatment risks, and management of androgen replacement therapy for the adult man are reviewed. The advantages and disadvantages of the various androgen delivery systems currently available and under investigation are discussed.

Exercise increases serum testosterone and sex hormone-binding globulin levels in older men

We examined the effects of moderate physical activity on serum luteinizing hormone (LH), sex hormone-binding globulin (SHBG), and testosterone levels in seven sedentary but otherwise healthy men aged 66 to 76 years (mean +/- SD, 70 +/- 4). Blood samples were obtained at 10-minute intervals for 4 hours before, during, and 4 hours after 60 minutes of cycle ergometry. Blood samples were also obtained every 10 minutes for 9 hours during a separate day to control for normal diurnal variation in serum testosterone levels. Serum testosterone increased 39%, SHBG 19%, total serum protein 13%, and the free testosterone index 23% during exercise (P < .01 for all). Testosterone and SHBG levels during the 4-hour sampling period after exercise were similar to values obtained before exercise and on the morning and afternoon of the control day. LH concentrations were unaltered during or after exercise. The change in SHBG levels during exercise correlated positively with the change in testosterone concentrations (r = .74, P = .09). We conclude that short-term exercise produces a transient elevation in serum testosterone levels in elderly men, which is partly due to an increase in serum SHBG concentrations. The concomitant increase in total protein and the rapid return of total protein and SHBG to baseline values after exercise indicate that hemoconcentration partly contributes to the exercise-associated increase in circulating testosterone levels.

Role of testosterone in the induction of hepatic peroxisome proliferation by clofibrate

Hepatic peroxisome proliferation is induced by a number of agents, including clofibrate. Sustained proliferation of peroxisomes is associated with the development of hepatocellular carcinoma. In the present study, we have investigated the role of testosterone in peroxisome proliferation induced by clofibrate. Three groups of male rats (intact, castrated, and castrated replaced with testosterone) were studied. Proliferation of peroxisomes was induced by feeding clofibrate (0.25%, 0.50%, and 1.0% of diet) for 2 weeks. Peroxisome proliferation was monitored by measuring total peroxisomal beta-oxidation activity. In intact rats, the peroxisomal beta-oxidation activity (nmol/min/mg protein) increased in a dose-dependent manner and was 7.2 +/- 0.4, 52.6 +/- 7.5, 63.2 +/- 3.7, and 92.4 +/- 4.0 at clofibrate doses of 0%, 0.25%, 0.50%, and 1.0%, respectively. In contrast, in castrated rats, the total peroxisomal beta-oxidation activity was significantly (P < .01) lower at clofibrate levels of 0.25% and 0.50% (25.8 +/- 2.7 and 42.5 +/- 2.2, respectively), but not at the clofibrate level of 1.0% (85.0 +/- 6.3). Testosterone replacement of castrated rats restored the peroxisomal beta-oxidation activity. To determine whether the above results were related to the metabolism of clofibrate in the absence or presence of testosterone, we measured serum clofibrate levels. These levels were 50% lower in castrated rats than in intact rats or in testosterone-treated castrated rats. The activity of hepatic uridine diphosphate (UDP)-glucuronyltransferase, the enzyme catalyzing the glucuronidation of clofibrate, was measured using either bilirubin or 4-methylumbelliferone as substrates and was found to be unaffected by castration or testosterone treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum androgens in intensive-care patients: correlations with clinical findings

Serum androgen levels were studied in 100 patients (50 male) with varying degrees of severe illness, determined by Acute Physiological and Chronic Health Evaluation (APACHE). Comparison with normal subjects revealed the following changes: (1) Basal dehydroepiandrosterone sulphate (DHEAS) values were decreased in the ill female patients (P less than 0.001) as well as in the ill males (two groups, P less than 0.01; P less than 0.05). Androstenedione values did not differ from the controls in patients of either sex. Basal testosterone levels were decreased in ill male patients (P less than 0.001), but not in females. (2) The low testosterone concentrations in the severely ill male patients correlated inversely with the APACHE score; additionally, a dependence on diagnostic categories could be demonstrated in men, since the lowest values were found in patients suffering from sepsis or liver cirrhosis. Acutely ill males had a moderately decreased testosterone, whereas chronically ill males showed a marked reduction of testosterone compared to the controls. Lowered DHEAS and androstenedione levels could be measured in chronically ill males but not in ill females. (3) 17 alpha-OH-progesterone and 17 alpha-OH-pregnenolone levels in subgroups of the patients suggested a probable enzymatic block in the delta 5-pathway of androgen biosynthesis in severe illness. The ratio of 17 alpha-OH-pregnenolone to DHEAS was significantly higher in male patients and tended to be high in ill females, whereas the ratio of 17 alpha-OH-progesterone to androstenedione showed no difference between healthy and ill subjects.

Biosynthesis of testicular steroids in the immature, adult and senescent guinea-pig

The potential biosynthetic capacity of testicular hormones was studied in immature, pubertal and aging guinea-pig. In their sexual development towards puberty, changes in the relationship of the steroids involved in the steroidogenic pathways were observed. The testosterone/androstenedione ratio changes markedly, showing an important increase with pubertal proximity. The testosterone in equilibrium androstenedione sequence, reversibly catalyzed by 17 beta-hydroxysteroid oxidoreductase (17 beta-oxido-reductase), clearly shifted towards androstenedione in immature animals irrespective of the precursor utilized. Post-pubertal animals showed a greater enzymatic activity in the 5-ene and 4-ene testicular synthesis pathways, testosterone production being greatest. In the aging animal, hormonal biosynthetic capacity falls. Reversion of the 17 beta-oxido-reductase activity could be one of the mechanisms responsible for the decrease in testosterone, as in immature guinea-pigs. In order to investigate the in vitro steroidogenic capacity of glands at different ages, minces of testicular tissue were incubated with labelled precursors. The studies were conducted in triplicate at 35 degrees C. For equal quantities of incubated tissue the non-metabolized amount of [3H]pregnenolone and [14C]progesterone, utilized as precursors, was different in post-pubertal and senescent animals: 55.7 +/- 3 vs 59.3 +/- 2.3% (P less than 0.01) for pregnenolone, and 50.1 +/- 3.3 vs 56.3 +/- 2.9% (P less than 0.01) for progesterone, respectively. Testosterone production was 12 +/- 2% in adult and 6.7 +/- 2.7% in senescent animals (P less than 0.01). The testosterone/androstenedione ratio was not significantly different in post-pubertal and senescent animals: 2.8 +/- 0.5 vs 2.4 +/- 0.4, but consistently higher than found in immature animals: 0.3 +/- 0.1. The lesser potential capacity of the aging tissue to synthesize testosterone could be explained by a decline in the glands capacity to metabolize the hormonal precursors.

Age-related decline of plasma bioavailable testosterone in adult men

Plasma bioavailable and total testosterone (T), gonadotropins (FSH, LH) and prolactin (PRL) were determined in 70 ambulatory men subdivided into 3 groups according to age: group I (n = 22; age 20-35 yr), group II (n = 22; age: 36-50 yr) and group III (n = 26; age 51-70 yr). Bioavailable T levels declined significantly with age (r = -0.42; P less than 0.01) while those of total T decreased less significantly (r = -0.28; P less than 0.05). In addition, the decrease of bioavailable T occurred earlier. FSH was shown to increase with age (r = 0.41; P less than 0.01) whereas LH and PRL were not found to change significantly. Bioavailable T was correlated with total T (r = 0.25; P less than 0.05) and inversely correlated with FSH (r = -0.26; P less than 0.05). No correlation could be demonstrated between LH and either bioavailable or total T. In view of the age-related increase of sex hormone binding globulin, a fact generally observed in the literature, bioavailable T may be considered a more reliable index than total T for the evaluation of T production. Thus it may be concluded that the early decrease of bioavailable T in ambulatory men not known to have any pathology or any medication altering testicular function corresponds in fact to age-related decline of T secretion by the testes.

Formation of 5,16-androstadien-3 beta-ol from pregnenolone in human testicular microsomes

A microsomal fraction of testicular tissue from a patient with prostatic carcinoma was incubated with [4-14C]pregnenolone in the presence of an NADPH-generating system for different periods of time. The metabolites were separated by Sephadex LH-20 column chromatography and then identified by thin-layer chromatography, radio-gas chromatography, and crystallization studies. Pregnenolone was converted to a major metabolite, 5-androstene-3 beta,17 beta-diol via 17-hydroxypregnenolone and then dehydroepiandrosterone. Another major metabolite was 5,16-androstadien-3 beta-ol, which increased with the time of incubation and accumulated in the incubation medium. After 120 min of incubation, 34.6% of the precursor was converted to 5-androstene-3 beta,17 beta-diol and 15.1% to 5,16-androstadien-3 beta-ol. In addition to the above-mentioned steroids, 16 alpha-hydroxypregnenolone, 5-pregnene-3 beta,20 alpha-diol, and 5-androstene-3 beta,17 alpha-diol were identified as minor metabolites of pregnenolone. From these results it was concluded that human testicular microsomes possess enzymic activities for the synthesis of 5,16-androstadien-3 beta-ol, as well as androgens from pregnenolone.

Concentrations of unconjugated 5 alpha-androstane-3 alpha, 17 beta-diol and 5 alpha-androstane-3 beta, 17 beta-diol and their precursor in human testicular tissue. Comparison with testosterone, 5 alpha-dihydrotestosterone, estradiol-17 beta, and with steroid concentrations in human epididymis

The concentrations of testosterone and its tissular metabolites were determined in testicular and epididymal tissue obtained from eleven male subjects (aged 65-85 years) after orchiectomy for prostatic cancer. The steroids were measured in different tissular compartments, i.e. testis, caput, corpus and cauda epididymis. The values (mean +/- SD; ng/g wet weight) were: Testosterone 724.0 +/- 286.0, 32.08 +/- 2.56, 41.45 +/- 1.77 and 32.24 +/- 2.14; 5 alpha-dihydrotestosterone 6.95 +/- 1.99, 9.76 +/- 2.33, 16.87 +/- 0.21 and 15.79 +/- 2.67; 5 alpha-androstane-3 alpha, 17 beta-diol 6.07 +/- 2.33, 2.17 +/- 0.24, 1.93 +/- 0.02 and 1.17 +/- 0.20; 5 alpha-androstane-3 beta, 17 beta-diol 56.66 +/- 20.97, 3.55 +/- 0.19, 2.21 +/- 0.27 and 3.34 +/- 0.32; estradiol-17 beta 5.36 +/- 3.0, 1.08 +/- 0.014, 1.44 +/- 0.038 and 1.47 +/- 0.03, respectively. Incubation of human testicular tissue with [3H]androst-5-ene-3 beta, 17 beta-diol or [3H]dihydrotestosterone showed that both androstane-diols were exclusively formed from dihydrotestosterone. Since high concentrations of 5 alpha-androstane-3 beta, 17 beta-diol are found in testicular tissue it is suggested that this steroid may be an index of seminiferous tubular function.

Testosterone and estradiol are co-secreted episodically by the human testis

In spite of a striking pulsatile pattern of luteinizing hormone (LH) secretion, testosterone (T) fluctuations in peripheral blood in normal adult men are irregular and of low amplitude. To determine whether T secretion by the human testis is episodic, T was measured in blood samples drawn at 15-min intervals for 4 h through a catheter placed in the testicular vein of six men with varicocele-associated infertility. Estradiol (E2) concentrations were also determined in each sample. Each subject released testosterone in well-defined pulses. Gonadal vein T levels ranged from 1 to 1,540 ng/ml. Mean (+/- SE) pulse amplitude was 176 +/- 42 ng/ml, with a frequency of 4.0 +/- 0.3 pulses per 4 h. Testicular vein E2 levels ranged from 0.01 to 6.8 ng/ml. E2 secretory episodes were generally coincident with T pulses, and their amplitudes were highly positively correlated (r = 0.90, P less than 0.01). These results indicate that T secretion by the adult human testis is pulsatile, and suggest a functional relationship between intermittent LH secretion and normal testicular steroidogenesis in men. The failure to appreciate these fluctuations as hormone pulses in peripheral blood may relate to their absolute amplitude and frequency. The concordance between E2 and T pulses suggests that the Leydig cell, under LH control, is the source of most of the E2 secreted by the adult human testis.

Blood and tissue steroid levels and their interrelationship in men with pathological conditions of the reproductive organs

We have investigated the interrelationship of the levels of 10 steroids in peripheral venous, spermatic arterial and spermatic venous blood, and in tissue specimens from the epididymis, vas deferens and testis from 8 patients who underwent orchidectomy for pathological conditions of the reproductive organs. The steroids analyzed by radioimmunoassay were: pregnenolone (5-P), dehydroepiandrosterone (DHEA), 17-hydroxyprogesterone (17-OH-P), androstenedione (A), testosterone (T), dihydrotestosterone (DHT) and the sulpho-conjugated forms (-S) of 5-P, DHEA, T and DHT. The quantitatively major steroids in peripheral venous blood were, in order of magnitude, DHEA-S, 5-P-S, DHT-S, T-S and T. No difference was observed between the levels of any of the steroids measured in peripheral venous and spermatic arterial blood. With the exception of DHEA-S and DHT-S, the levels of all steroids in spermatic venous blood were substantially higher than in peripheral venous blood (P less than 0.001). No correlation was found between steroid levels in spermatic venous and peripheral venous blood. Steroid concentrations in tissue from the epididymis, vas deferens and testis were markedly higher than in peripheral venous blood (P less than 0.01 to P less than 0.001), except for the levels of DHEA-S which were about equal in the various blood and tissue specimens. Tissue to blood ratios varied from approximately 2.0 to 500 according to the steroid in question. The peripheral blood levels of 5-P-S, DHEA-S and DHT-S were substantially higher than respective unconjugated steroid levels (P less than 0.001); the ratios (sulpho-conjugated to unconjugated) were approximately 17, 215 and 30, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Intratesticular unconjugated steroids in elderly men

As an extension of our studies on the influence of age on testicular function and with the aim of detecting whether the decline in testosterone production by aged testes is accompanied by a block in the biosynthetic chain leading from cholesterol to testosterone, we determined in the testis of young and elderly men, who died suddenly either from a cardiac incident or from accident, intratesticular steroids: pregnenolone, 17 hydroxypregnenolone (3 beta, 17 alpha-dihydroxy-5-pregnen-20-one), dehydroepiandrosterone, androstenediol, (5-androsten-3 beta, 17 beta-diol), progesterone, 17 hydroxyprogesterone, androstenedione, 17 beta-estradiol as well as testosterone, dihydrotestosterone (5 alpha-androstan-17 beta-ol-3-one) and androstanediol (5 alpha androstane-3 alpha, 17 beta-diol). The intratesticular steroid pattern in elderly men was essentially characterized by a decrease of the 5-ene steroid concentration, whereas we did not observe a decrease in the 4-ene steroids, progesterone concentration being even significantly higher in the aged testes. There was no evidence for a decrease in either lyase or 17-hydroxylase activity. It is suggested that the steroid pattern as observed in the aged testes is the consequence of a decreased oxygen supply, due to a decreased testicular perfusion.

Impaired in vitro testicular endocrine function in elderly men

Measurements of testosterone concentrations in peripheral and spermatic venous blood have yielded conflicting results concerning testosterone production in elderly men. To further elucidate the testicular endocrine capacity during aging, peripheral serum hormone levels and the in vitro conversion of progesterone and pregnenolone in histopathologically normal testicular tissue have been investigated in 22 elderly men and 28 younger adult males. The conversion mediated by 3 beta-hydroxysteroid-dehydrogenase and 17 alpha-hydroxylase was significantly higher (p less than 0.05 and p less than 0.01 respectively) in testicular tissue from the younger adult men, than in testicular tissue from elderly men. Since serum LH levels were significantly higher (p less than 0.01) and serum testosterone levels were significantly lower (p less than 0.01) in the elderly men, these data indicate that there was a primary endocrine impairment at the testicular level in the elderly men.

In vitro conversion of progesterone in the human testis at different ages, pathophysiological conditions, and during treatment with estrogens or gonadotrophic hormones

The enzyme 17 alpha-hydroxylase catalyzes the conversion of progesterone to 17 alpha-hydroxyprogesterone in the testis and may be studied with the use of incubation of testicular tissue with [3H] progesterone in vitro. The enzyme 20 alpha-hydroxysteroid dehydrogenase catalyzes the conversion of progesterone to 20 alpha-dihydroprogesterone. These enzymes were studied in testicular tissue from 105 human males regarding the effects of aging, different pathophysiological conditions, and gonadotrophic or estrogenic treatment. 17 alpha-Hydroxylase activity was low in vitro in testicular tissue from prepubertal boys, adult men with pituitary tumors, and estrogen-treated elderly men. In nontreated elderly men and certain infertile adult men, 17 alpha-hydroxylase was more active than in the above-mentioned patient groups, albeit lower than in adolescent and adult men. Gonadotropic treatment increased the conversion mediated by 17 alpha-hydroxylase in prepubertal as well as adult testicular tissue. In conclusion, the activity of 17 alpha-hydroxylase may be influenced by gonadotrophic hormones and may be an indicator of the testicular endocrine state at the moment of biopsy. Testicular 20 alpha-hydroxysteroid dehydrogenase seems to be active during low gonadotrophic influence and might even be inhibited by gonadotrophic stimulation.

Histopathological and morphometrical study of the human epididymis and testis

Histopathological and morphometrical observations of the epididymis and testis were performed on 159 autopsy cases and 3 surgical materials of orchiectomy. The serum values of testosterone, FSH, LH, and values of intratesticular testosterone were measured in a certain number of the cases. Concerning the epididymis, increasing arteriosclerotic change was observed in the older epididymis. A high incidence of hyalinization of small arteries and arterioles was found in the younger epididymis. Eosinophilic microbodies were seen in the epithelial nuclei of the ductus epididymidis with high incidence in the older age groups. They were thought to be a catabolic compound containing phospholipids and protein resulting from cell degeneration of the mucosal epithelium. The diameter of the ductus epididymidis decreased with age. Inflammatory changes and ensued periductal sclerosis were found in the efferent duct area with an extremely high incidence. Serum values of testosterone correlated with both the age and morphological scoring calculated on the basis of either clusters or individual Leydig cells. Furthermore, testicular volume was inversely correlated with age.

The gonadotropin-suppressive activity of androgen is increased in elderly men

The influence of aging on the responsiveness to sex steroid hormones in men was studied by comparing circulating gonadotropin concentrations, pulsatile LH release, and sex hormone-binding globulin (TeBG) levels. This was done before and during a four-day continuous infusion of testosterone (T) (7.5 mg/d), dihydrotestosterone (DHT) (7.0 mg/d), or estradiol (E2) (45 micrograms/d) in young adult men, ages 18 to 32, and healthy elderly men, ages 65 to 80. DHT reduced mean serum LH and FSH levels as well as the frequency of spontaneous LH secretory episodes to a greater extent (p less than 0.05) in old men than in young men. T administration also reduced serum LH levels more in aged than in young men (P less than 0.05); however, this difference was less pronounced than for DHT. During T infusion, the decrease in serum FSH levels was similar in the two groups. Spontaneous LH pulse amplitude also declined during both T and DHT infusion in aged, but not in young men. By contrast, infusion of E2 reduced both serum LH and FSH levels comparably in aged and young men. DHT infusion also reduced serum TeBG levels equally in old and young men. Finally, each steroid infusion produced comparable mean circulating levels of T, DHT, and E2 in both groups. These data indicate that elderly men are more responsive than are young men to the gonadotropin-suppressive effects of androgen, but not to DHT effects on circulating TeBG levels. The more pronounced deceleration of spontaneous LH secretory episodes during DHT infusion in aged men provides evidence for an alteration in hypothalamic function in male senescence.

Basal and adrenocorticotropic hormone-stimulated serum 17 alpha-hydroxyprogesterone in men with idiopathic infertility

Basal serum 17 alpha-hydroxyprogesterone (17-OHP) concentrations and the 17-OHP response to acute adrenocorticotropic hormone administration were studied in infertile men with idiopathic oligospermia to determine the prevalence of attenuated 21-hydroxylase deficiency. Mean (+/- standard error of the mean) basal serum 17-OHP levels in 50 infertile men (1.17 +/- 0.06 ng/ml) and 25 normal volunteers (1.09 +/- 0.08 ng/ml) were indistinguishable (not significant). However, two infertile men had 17-OHP levels which were above the normal range. Following the intravenous administration of 0.25 mg of synthetic adrenocorticotropic hormone (cosyntropin) to these two men and to eight additional infertile men, the mean increase in 17-OHP concentrations was 0.84 +/- 0.15 ng/ml, a response which was similar to that of normal men (0.94 +/- 0.26 ng/ml). No patient demonstrated the minimum fourfold rise in 17-OHP previously reported in men with attenuated 21-hydroxylase deficiency, suggesting the absence of this disorder among these subjects. This study suggests that subtle 21-hydroxylase deficiency is rare among infertile men with idiopathic infertility.

Steroidogenesis in the monkey testis: relationship of enzyme organization to endogenous steroids, steroidogenesis and gonadotropin treatment

To explore testicular factors which determine steroidogenesis, circulating and intratesticular steroid levels were measured and in vitro steroidogenesis in testicular mines and microsomes was investigated using adult rhesus monkeys before and after treatment with pharmacological doses of hCG or hCG together with hMG. After gonadotropin treatment serum and intratesticular levels of 17 alpha-hydroxyprogesterone as well as end product testosterone were markedly elevated. Dynamic studies revealed that 17 alpha-hydroxyprogesterone produced from pregnenolone was partly metabolized to C19-steroids but almost no 17 alpha-hydroxyprogesterone produced from progesterone was utilized by C17-20 lyase. Androstenedione levels increased in serum after both treatments and were elevated in testis tissue after hCG treatment. Androstenedione accumulated in vitro during incubation of untreated and hCG-treated testes with [3H]pregnenolone and [14C]progesterone. The major portion of the accumulated androstenedione was produced from pregnenolone through dehydroepiandrosterone rather than through 17 alpha-hydroxyprogesterone, indicating differential availability of androstenedione to 17 beta-hydroxysteroid oxidoreductase according to its origin. The 3H/14C ratio in product androstenedione was much greater than the ration in product testosterone in both untreated and hCG-treated testis; in testes of animals treated with hCG together with hMG, the ratios in both products were closely linked. Among the enzymes examined, 17 alpha-hydroxylase and C17-20 lyase activities for 5-ene-C21-steroids were increased and 17 beta-hydroxysteroid oxidoreductase activity were decreased by gonadotropin treatment. Our findings confirm the phenomenon of unequal substrate availability to enzymes depending upon the provenance of the substrate and demonstrate that gonadotropin(s) change substrate availability as do direct changes in enzyme activities. The unequal substrate availability validates the assumption, previously proposed by others, that microsome enzymes have an organized arrangement as enzyme complexes.

Seasonal changes in steroidogenesis in the testis of the rhesus monkey (Macaca mulatta)

To investigate the influence of seasonal changes from breeding to nonbreeding season on testicular steroidogenesis in the adult rhesus monkey, two animals were hemiorchidectomized in November and the second testis of each was removed the following April. Intratesticular steroid concentrations related to the formation of testosterone from pregnenolone were measured by radioimmunoassay. Related steroidogenic enzyme activities were also assayed and dynamic studies of the bioconversion of radiolabeled precursor steroids by testicular microsomes were performed. Testosterone was synthesized from pregnenolone through both dehydroepiandrosterone and 17 alpha-hydroxyprogesterone. No distinct differences were found in the testosterone biosynthetic pathway between testes in breeding and nonbreeding seasons. In the breeding season, intratesticular testosterone concentrations, the sum of intratesticular steroids measured, and the ratio of testosterone to the steroid sum were increased when compared to those in the nonbreeding season. No major seasonal changes in microsome enzyme activities were found, although enzyme activities, except for delta 5-3 beta-hydroxysteroid dehydrogenase for C21-steroids, were slightly higher in the breeding season. We conclude that increased testosterone production in the testis during the breeding season is due primarily to increased pregnenolone supply from Leydig cell mitochondria and, to a lesser extent, to an enhanced pregnenolone bioconversion to testosterone in the microsomes.