Age related changes in the pituitary-testicular axis in normal men; lower serum testosterone results from decreased bioactive LH drive

Testosterone concentrations and associated predictors in men with cystic fibrosis: A retrospective, single-center study

BACKGROUND

Men with cystic fibrosis (CF) have sexual health concerns such as delayed puberty, infertility, and hypogonadism. The causes and prevalence of hypogonadism have not been well studied. The purpose of this study was to determine the prevalence of a low testosterone concentration in men with CF.

METHODS

This retrospective study was approved by the Emory University Institutional Review Board (IRB). Data were extracted from the electronic medical records of adult men with CF receiving care at the Emory Cystic Fibrosis Center. A total of 129 men with CF were followed at our center from 2016 to 2023. Of these individuals, 76 men with CF (58.9%) had at least one serum total testosterone measurement. Seven individuals were excluded from this study since they were currently receiving testosterone therapy, leaving a final sample size of 69 individuals for the analysis. Demographic data, serum testosterone concentrations, and other factors associated with low testosterone concentrations were collected. Low testosterone was defined as a value below 300 ng/dL. Regression analyses were used to determine factors associated with low testosterone levels.

RESULTS

The mean (± SD) age of the 69 eligible participants was 33.34 ± 10.98 years. The mean testosterone concentration was 421 ± 158.5 ng/dL with 27.54 percent of men with a testosterone value below 300 ng/dL. The mean hemoglobin level was 14.23 ± 2.18 g/dL. Testosterone levels were positively related to hemoglobin levels. Time of day of measurement and age were not associated with testosterone levels.

CONCLUSION

Roughly a quarter of men with CF demonstrated low testosterone in our sample. Low hemoglobin was associated with low testosterone levels in men with CF. Neither time of day nor age influenced testosterone concentrations in this sample.

Effects of biological sex and pregnancy in experimental autoimmune encephalomyelitis: It's complicated

Experimental autoimmune encephalomyelitis (EAE) can be induced in many animal strains by inoculation with central nervous system antigens and adjuvant or by the passive transfer of lymphocytes reactive with these antigens and is widely used as an animal model for multiple sclerosis (MS). There are reports that female sex and pregnancy affect EAE. Here we review the effects of biological sex and the effects of pregnancy on the clinical features (including disease susceptibility) and pathophysiology of EAE. We also review reports of the possible mechanisms underlying these differences. These include sex-related differences in the immune system and in the central nervous system, the effects of hormones and the sex chromosomes and molecules unique to pregnancy. We also review sex differences in the response to factors that can modify the course of EAE. Our conclusion is that the effects of biological sex in EAE vary amongst animal models and should not be widely extrapolated. In EAE, it is therefore essential that studies looking at the effects of biological sex or pregnancy give full information about the model that is used (i.e. animal strain, sex, the inducing antigen, timing of EAE induction in relation to pregnancy, etc.). In addition, it would be preferable if more than one EAE model were used, to show if any observed effects are generalizable. This is clearly a field that requires further work. However, understanding of the mechanisms of sex differences could lead to greater understanding of EAE, and suggest possible therapies for MS.

Nandrolone Supplementation Promotes AMPK Activation and Divergent 18[FDG] PET Brain Connectivity in Adult and Aged Mice

Decreased anabolic androgen levels are followed by impaired brain energy support and sensing with loss of neural connectivity during physiological aging, providing a neurobiological basis for hormone supplementation. Here, we investigated whether nandrolone decanoate (ND) administration mediates hypothalamic AMPK activation and glucose metabolism, thus affecting metabolic connectivity in brain areas of adult and aged mice. Metabolic interconnected brain areas of rodents can be detected by positron emission tomography using ¹⁸FDG-mPET. Albino CF1 mice at 3 and 18 months of age were separated into 4 groups that received daily subcutaneous injections of either ND (15 mg/kg) or vehicle for 15 days. At the in vivo baseline and on the 14th day, brain ¹⁸FDG-microPET scans were performed. Hypothalamic pAMPK^T172/AMPK protein levels were assessed, and basal mitochondrial respiratory states were evaluated in synaptosomes. A metabolic connectivity network between brain areas was estimated based on ¹⁸FDG uptake. We found that ND increased the pAMPK^T172/AMPK ratio in both adult and aged mice but increased ¹⁸FDG uptake and mitochondrial basal respiration only in adult mice. Furthermore, ND triggered rearrangement in the metabolic connectivity of adult mice and aged mice compared to age-matched controls. Altogether, our findings suggest that ND promotes hypothalamic AMPK activation, and distinct glucose metabolism and metabolic connectivity rearrangements in the brains of adult and aged mice.

[Testosterone replacement therapy and its relationship with hyperestrogenism and obesity. Problems of laboratory diagnostics of hyperestrogenism]

Testosterone replacement therapy (TRT) is one of the most effective and common treatments for testosterone deficiency today. It is often prescribed, focusing only on the level of testosterone and the presence of patient complaints about a decrease in sexual function. Quite rarely, doctors additionally assess the level of estradiol and, as a consequence, the initial presence of a symptom of hyperestrogenism. One of the likely consequences of the appointment of TRT may be an excess of estradiol, the excess formation of which is associated with the enzyme aromatase, which converts testosterone into estradiol. Despite the availability of laboratory determination of the level of estradiol, the result may not always coincide with the clinical picture, one of the reasons is the difference in the methods for determining the level of estradiol in each laboratory, there is no single standard or «reference» today. This article describes the evolution of TRT, and also focuses on the variability of estradiol levels from laboratory to laboratory, and explains in detail why the assessment of estradiol over time should be carried out in only one laboratory. A systematic literature search was carried out in the databases Medline, Scopus, Web of Science and Elibrary, CyberLeninka.The purpose of our review was the need to engage the attention of specialists to the problem of hyperestrogenism, the not always justified prescription of TRT in patients with obesity, hypogonadism and hyperestrogenism, as well as to the problem of laboratory diagnosis of hyperestrogenism, which is acute not only in our country, but all over the world.

The dynamic changes of Nrf2 mediated oxidative stress, DNA damage and base excision repair in testis of rats during aging

Accumulation of oxidative stress, DNA damage and impaired DNA repair appear to play critical roles in the decline of testicular function with aging. However, when those factors begin to lose control in testis during aging has not yet been well understood. This study was designed to assess the changes of oxidative stress and DNA damage status, and DNA repair capacity in testis during aging. Thus, male Sprague-Dawley rats at 3, 9, 15 and 24 months of age were used to delineate the dynamic changes in testicular weight and index, testosterone concentration, testicular histology, Nrf2-mediated oxidative stress, DNA damage, DNA repair and apoptosis. Results showed that testicular weight and index, testosterone concentration and spermatid number progressively declined from 9 to 24 months of age. Similarly, seminiferous tubule diameters and seminiferous epithelium heights gradually diminished with aging. Nrf2-mediated antioxidant defense ability was significantly impaired in testis with increasing age including decreased the activity of SOD and the expression levels of Nrf2, HO-1 and NQO-1, and increased the contents of MDA. In addition, DNA damage including DNA single-strand breaks (SSBs) and DNA double-strand breaks (DSBs) also progressively increased accompanied by increased levels of 8-hydroxydeoxyguanosine (8-OHdG) and γ-H2AX, and activated ATM/Chk2 and ATR/Chk1 pathway. Consistent with the results of Nrf2 pathway, the expression levels of APE1, OGG1 and XRCC1 involved in base excision DNA repair (BER) pathway increased from 3 to 9 months of age, and then gradually decreased after 9 months of age. Finally, TUNEL and Western blot results further confirmed germ cell apoptosis progressively increased from 3 to 24 months of age as evidenced by decreased ratio of Bcl-2/Bax and levels of Bcl-2 expression, and increased Bax expression levels. Taken together, our results suggest that downregulation of antioxidant ability mediated by Nrf2 pathway and impairment of BER capacity might correlate with increased DNA damage, and then induce declining testicular function during aging after adult.

Comparison of Anthropometric Measures for Evaluating the Association Between Hypogonadism and Hypothalamic-Pituitary-Gonadal Hormones in a Taiwanese Population

To investigate the degree of association between levels of sex hormones and anthropometric indices in male population. A cross-sectional survey was conducted between July 2014 and July, 2016, in a men's health polyclinic in Taiwan. Body mass index, waist circumference, waist-to-height ratio (WHtR), and conicity index were tested. Serum total testosterone, free testosterone, and dehydroepiandrosterone sulfate (DHEA-S) were measured. Decreased testosterone levels were correlated with the four indices (r = -0.09 to -0.27, p < 0.01). In hypogonadism group, DHEA-S deficiency was associated with older age, higher anthropometric indices, and chronic illness. The areas under the receiver operating characteristic curves of hypogonadism and DHEA-S deficiency by the four anthropometric indices ranged from 52.5% to 65.9%. Logistic regression analysis revealed that obesity, defined by the four indices, was associated with increased risk of hypogonadism. Moreover, obesity was also associated with increased risk and DHEA-S deficiency. Anthropometric indices analyzed are associated with lower testosterone and DEAH-S deficiency. A WHtR of 0.5 is suggested to be a simple and reliable indicator of hypogonadism and DHEA-S deficiency.

Quantitative (stereological) study of the epididymis and seminal vesicle in the rat from young to old

There is a scarcity of morphometric data on the developmental and ageing changes in the epididymis and seminal vesicle in young and old rats. Eighty-six normal male Sprague-Dawley rats were randomly sampled from a cohort of animals aged 1-36 months (7-9 animals each age group). The epididymis and seminal vesicle (with the closely attached coagulating gland) were removed, and methacrylate resin-embedded sections were prepared for quantitative study of key histological structures by light microscopy. Stereological methods (point counting and optical disector) were used to estimate the total volumes of sperm mass, secretion (glandular lumen) and other structures and the number of spermatozoa. The results showed that the rapid growth of the reproductive organs was between 1 and 4 months of age. The epididymis stored the largest volume of sperm mass or number of spermatozoa at 12 months of age, but thereafter until 36 months of age, the sperm storage did not markedly diminish. The volume of secretion stored in the seminal vesicular gland declined by more than 35% from a plateau at 12-18 months until 36 months of age while that in the coagulating gland declined by more than 30% from a plateau at 18-24 months until 36 months of age.

The impact of luteinizing hormone supplementation in gonadotropin-releasing hormone antagonist cycles: a retrospective cohort study

The impact of exogenous luteinizing hormone (LH) supplementation to patients undergoing controlled ovarian stimulation with gonadotropin-releasing hormone (GnRH) antagonists on cycle outcomes is controversial. Here, we present a retrospective cohort study including cycles from December 2015 to December 2016. Totally 320 cycles were divided into two groups according to with or without exogenous LH supplementation. No significant differences regarding the number of retrieved oocytes, the number of good-quality embryos, and clinical pregnancy rate between the two groups were found. The logistic regression analysis revealed that LH supplementation was not independently associated with clinical pregnancy rate (OR = 0.577, 95% CI: 0.272-1.222, p = .58) or a biochemical pregnancy rate (OR = 0.922, 95% CI: 0.444-1.916, p = .83). When patients were divided into subgroups based on age, more retrieved oocytes (5.60 vs. 3.97, p = .04) and good-quality embryos (3.07 vs. 1.93, p = .01) were achieved in cycles with exogenous LH supplementation for 40 years and over group. We conclude that for aged women (40 years old and over), LH supplementation has a positive impact on the number of retrieved oocytes and good-quality embryos in GnRH antagonist cycles.

Pharmacological regulation of the cholesterol transport machinery in steroidogenic cells of the testis

Reduced serum testosterone (T), or hypogonadism, is estimated to affect about 5 million American men, including both aging and young men. Low serum T has been linked to mood changes, worsening cognition, fatigue, depression, decreased lean body mass and bone mineral density, increased visceral fat, metabolic syndrome, decreased libido, and sexual dysfunction. Administering exogenous T, known as T-replacement therapy (TRT), reverses many of the symptoms of low T levels. However, this treatment can result in luteinizing hormone suppression which, in turn, can lead to reduced sperm numbers and infertility, making TRT inappropriate for men who wish to father children. Additionally, TRT may result in supraphysiologic T levels, skin irritation, and T transfer to others upon contact; and there may be increased risk of prostate cancer and cardiovascular disease, particularly in aging men. Therefore, the development of alternate therapies for treating hypogonadism would be highly desirable. To do so requires greater understanding of the series of steps leading to T formation and how they are regulated, and the identification of key steps that are amenable to pharmacological modulation so as to induce T production. We review herein our current understanding of mechanisms underlying the pharmacological induction of T formation in hypogonadal testis.

Gender differences in autoimmune disease

Autoimmune diseases are a range of diseases in which the immune response to self-antigens results in damage or dysfunction of tissues. Autoimmune diseases can be systemic or can affect specific organs or body systems. For most autoimmune diseases there is a clear sex difference in prevalence, whereby females are generally more frequently affected than males. In this review, we consider gender differences in systemic and organ-specific autoimmune diseases, and we summarize human data that outlines the prevalence of common autoimmune diseases specific to adult males and females in countries commonly surveyed. We discuss possible mechanisms for sex specific differences including gender differences in immune response and organ vulnerability, reproductive capacity including pregnancy, sex hormones, genetic predisposition, parental inheritance, and epigenetics. Evidence demonstrates that gender has a significant influence on the development of autoimmune disease. Thus, considerations of gender should be at the forefront of all studies that attempt to define mechanisms that underpin autoimmune disease.

Gonadotropin therapy in assisted reproduction: an evolutionary perspective from biologics to biotech

Gonadotropin therapy plays an integral role in ovarian stimulation for infertility treatments. Efforts have been made over the last century to improve gonadotropin preparations. Undoubtedly, current gonadotropins have better quality and safety profiles as well as clinical efficacy than earlier ones. A major achievement has been introducing recombinant technology in the manufacturing processes for follicle-stimulating hormone, luteinizing hormone, and human chorionic gonadotropin. Recombinant gonadotropins are purer than urine-derived gonadotropins, and incorporating vial filling by mass virtually eliminated batch-to-batch variations and enabled accurate dosing. Recombinant and fill-by-mass technologies have been the driving forces for launching of prefilled pen devices for more patient-friendly ovarian stimulation. The most recent developments include the fixed combination of follitropin alfa + lutropin alfa, long-acting FSH gonadotropin, and a new family of prefilled pen injector devices for administration of recombinant gonadotropins. The next step would be the production of orally bioactive molecules with selective follicle-stimulating hormone and luteinizing hormone activity.

Older men exhibit reduced efficacy of and heightened potency downregulation by intravenous pulses of recombinant human LH: a study in 92 healthy men

Direct sampling of the human spermatic veins has disclosed concomitant LH and testosterone (T) pulses, suggesting pulsatile LH concentration-dependent stimulation of T secretion. However, studies to date have examined this hypothesis using only pharmacological stimulation with hCG. The present study tests the hypothesis that age is marked by decreased T secretory responses to repeated near-physiological iv pulses of recombinant human LH administered in a Clinical Translational Science Center. Participants included 92 healthy men aged 18-75 yr with BMI 18-34 kg/m(2). The contribution of endogenous LH pulses was minimized by combined injection of a selective GnRH receptor antagonist sc and successive pulses of biosynthetic LH iv. A new analytical dose response model was applied to estimate the properties of exogenous LH's drive of T secretion. Regression of LH-T dose response potency estimates on age showed that the efficacy of pulses of biosynthetic LH progressively decreased with age (P = 0.014, r = 0.26). Testis sensitivity to exogenous LH pulses also declined with age (P = 0.011, r = 0.27). Moreover, estimated Leydig cell downregulation by LH pulses rose significantly with age (P = 0.039, r = 0.22). These outcomes were selective, since the recovery potency of infused LH was not affected by age but was reduced by increasing BMI (P = 0.011, r = 0.27). Assuming stable bioactivity of infused recombinant human LH, these novel data indicate that factors associated with age and BMI attenuate LH efficacy and testis sensitivity and augment Leydig cell downregulation in healthy men.

Who needs LH in ovarian stimulation?

LH plays a key role in the intermediate-late phases of folliculogenesis. Although ovarian stimulation is efficiently achieved in most cases by the administration of exogenous FSH alone, specific subgroups of women may benefit from LH activity supplementation during ovarian stimulation. Some authors have found improved outcome with LH activity supplementation in advanced reproductive age women. Experience suggests that in about 10-12% of young normogonadotrophic patients treated with a gonadotrophin-releasing hormone agonist (GnRH-a) long protocol plus recombinant FSH human (r-hFSH), a 'steady response' is observed. In this subgroup of women, a higher number of oocytes is retrieved when daily LH activity supplementation is given from stimulation day 8, if compared with the standard FSH dose increase. Another subgroup of patients who may benefit from LH activity supplementation are those at risk for poor ovarian response treated with GnRH antagonist. Recent data demonstrate that in these women, when GnRH is administered in a flexible protocol, the concomitant addition of recombinant human LH improves the number of mature oocytes retrieved, when compared with the standard GnRH-a flare-up protocol. Thus, well calibrated LH administration improves the ovarian outcome in patients >35 years, in those showing an initial abnormal ovarian response to r-hFSH monotherapy, and in 'low prognosis' women treated with GnRH antagonists.

Sexual experience changes sex hormones but not hypothalamic steroid hormone receptor expression in young and middle-aged male rats

Testosterone is well known to regulate sexual behavior in males, but this is dependent upon prior sexual experience. Aging is associated with decreased libido and changes in testosterone, but the role of experience in these age-related processes has not been systematically studied. We examined effects of age and sexual experience on serum hormones (total testosterone, free testosterone, estradiol, LH) and on numbers of androgen receptor (AR) and estrogen receptor alpha (ERalpha) immunoreactive cells in the hypothalamus. Extensive sexual experience was given to male rats at 4 months of age. Rats were euthanized at either 4 months (young) or 12 months (middle-aged (MA)). Comparable sexually naïve male rats were handled and placed into the testing arena but did not receive any sexual experience. Thus, we had four groups: young-naïve, young-experienced, MA-naïve and MA-experienced. Serum hormone levels were assayed, and numbers of AR and ERalpha cells were quantified stereologically in the medial preoptic nucleus (MPN) and the anteroventral periventricular nucleus (AVPV). Sexually experienced males had significantly elevated serum testosterone and free testosterone in both age groups. Both total and free testosterone were higher, and estradiol lower, in middle-aged than young rats. Experience did not alter either AR or ERalpha expression in the preoptic brain regions studied. Aging was associated with increased expression of AR, but no change in ERalpha. These results show that sexual experience can induce short-term and long-term alterations in serum hormones but these effects are not manifested upon their receptors in the hypothalamus.

Clomiphene citrate and testosterone gel replacement therapy for male hypogonadism: efficacy and treatment cost

INTRODUCTION

The efficacy of oral clomiphene citrate (CC) in the treatment of male hypogonadism and male infertility (MI) with low serum testosterone and normal gonadotropin levels has been reported.

AIM

The aim of this article is to evaluate CC and testosterone gel replacement therapy (TGRT) with regard to biochemical and clinical efficacy and cost.

MAIN OUTCOME MEASURES

The main outcome measures were change in serum testosterone with CC and TGRT therapy, and change in the androgen deficiency in aging male (ADAM) questionnaire scores with CC therapy.

METHODS

Men receiving CC or TGRT with either Androgel 1% or Testim 1% for hypogonadism (defined as testosterone < 300 ng/mL) or MI were included. Serum values were collected 1-2 months after treatment initiation and semi-annually thereafter. Retrospective data collection was performed via chart review. Subjective follow up of patients receiving CC was performed via telephone interview using the ADAM questionnaire.

RESULTS

A hundred and four men (65 CC and 39 TGRT) were identified who began CC (50 mg every other day) or TGRT (5 g). Average age (years) was 42(CC) vs. 57 (TGRT). Average follow up was 23 months (CC, range 8-40 months) vs. 46 months (TGRT, range 6-149 months). Average posttreatment testosterone was 573 ng/dL in the CC group and 553 ng/dL in the TGRT group (P value < 0.001). The monthly cost of Testim 1% (5 gm daily) is $270, Androgel 1% (5 gm daily) is $265, and CC (50 mg every other day) is $83. Among CC patients, the average pretreatment ADAM score was 4.9 vs. 2.1 at follow up (P < 0.05). Average pretreatment ADAM sexual function domain score was 0.76 vs. 0.23 at follow up (P < 0.05). There were no adverse events reported.

CONCLUSION

CC represents a treatment option for men with hypogonadism, demonstrating biochemical and clinical efficacy with few side effects and lower cost as compared with TGRT.

Demographic, physical and lifestyle factors associated with androgen status: the Florey Adelaide Male Ageing Study (FAMAS)

OBJECTIVE

Plasma androgen levels are inversely associated with health in men, the age-related decline of which may result from factors other than ageing per se. This study aimed to determine the effects of demographic, physical and lifestyle factors on age-related androgen status in men.

DESIGN

An observational survey of a regionally representative male population residing in the North West regions of Adelaide, Australia.

PARTICIPANTS

Study sample includes 1195 men aged 35-81 years with a response rate of 45.1%.

MEASUREMENTS

Plasma levels of total testosterone (TT), bioavailable testosterone (BT), SHBG, insulin-like peptide 3 (INSL3), and gonadotrophins were measured along with an extensive list of demographic, physical and lifestyle factors including body composition, muscle strength and biomarkers of chronic diseases, physical activity, nutrition and smoking behaviour.

RESULTS

Low TT was mostly associated with high abdominal fat and triglycerides and low muscle strength rather than ageing per se. Low BT was associated with increased age followed by high whole body fat percentage. BT and TT levels were higher in unmarried men and smokers. SHBG levels increased with age, but were also inversely associated with insulin and triglycerides. The Leydig cell specific factor INSL3 was the strongest biomarker associated with both TT and BT.

CONCLUSIONS

Factors associated with low androgen status variably include high body fat percentage, low muscle strength and biomarkers of the metabolic syndrome. Reducing exposure to factors that adversely affect androgen status may improve the general health of ageing men by mechanisms yet to be defined.

The aging male hypothalamic-pituitary-gonadal axis: pulsatility and feedback

Aging results in insidious decremental changes in hypothalamic, pituitary and gonadal function. The foregoing three main anatomic loci of control are regulated by intermittent time-delayed signal exchange, principally via gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH) and testosterone/estradiol (Te/E(2)). A mathematical framework is required to embody these dynamics. The present review highlights integrative adaptations in the aging male hypothalamic-pituitary-gonadal axis, as assessed by recent objective ensemble models of the axis as a whole.

Understanding the role of LH: myths and facts

This review summarizes a series of lectures given at a recent Continuing Medical Education meeting in Hamburg, Germany (May 2007), aiming to understand the role of luteinizing hormone (LH) in follicular development during the natural menstrual cycle and controlled ovarian stimulation. Clinical situations and target groups of patients who might benefit from LH supplementation during their ovarian stimulation were discussed and defined. The lectures updated knowledge on the physiology of LH during the normal menstrual cycle and the role of LH in ovarian stimulation. The concept of the 'LH window' was presented, and the use of LH supplementation in different groups of patients undergoing controlled ovarian stimulation was discussed, including those with advanced age, hypogonadotrophic hypogonadism, pituitary down-regulation and poor response. In addition, the different ways of using LH or human chorionic gonadotrophin supplementation in ovulation induction protocols were described.

Age attenuates testosterone secretion driven by amplitude-varying pulses of recombinant human luteinizing hormone during acute gonadotrope inhibition in healthy men

CONTEXT

Whether testosterone (Te) depletion in aging men reflects deficits in the testis, hypothalamus, and/or pituitary gland is unknown.

OBJECTIVE

Our objective was to quantify the impact of age on gonadal Te secretion driven by amplitude-varying pulses of recombinant human LH (rhLH) in the absence of confounding by endogenous hypothalamo-pituitary signals.

DESIGN

This was a double-blind, placebo-controlled study.

SETTING

The setting was an academic medical center.

SUBJECTS

Fifteen healthy community-dwelling men ages 22-78 yr were included in the study.

INTERVENTION

Saline or four separate rhLH doses were each infused twice iv in randomized order as one pulse every 2 h over 20 h to stimulate Te secretion, after LH secretion was suppressed by a GnRH-receptor antagonist, ganirelix.

MAIN OUTCOME

LH and Te concentrations were determined in blood samples collected every 5 min. Maximal and minimal (as well as mean) Te responses were regressed linearly on age to reflect LH peak and nadir (and average) effects, respectively.

RESULTS

The ganirelix/rhLH paradigm yielded serum LH concentrations of 4.6 +/- 0.22 IU/liter (normal range 1-9). By regression analysis, age was associated with declines in rhLH pulse-stimulated peak and nadir (and mean) concentrations of total Te (P = 0.0068), bioavailable Te (P = 0.0096), and free Te (P = 0.013), as well as lower Te/LH concentration ratios (P < 0.005). Deconvolution analysis suggested that the half-life of infused LH increases by 12%/decade (P = 0.044; R(2) = 0.28).

CONCLUSIONS

Infusion of amplitude-varying pulses of rhLH during gonadal-axis suppression in healthy men unmasks prominent age-related deficits in stimulated total (39%), bioavailable (66%), and free (63%) Te concentrations, and a smaller age-associated increase in LH half-life. These data suggest that age-associated factors reduce the efficacy of LH pulses.

Evidence for thyroid hormone as a positive regulator of serum thyrotropin bioactivity

CONTEXT

The regulation of TSH bioactivity in humans is not completely understood.

OBJECTIVE

The aim of the study was to investigate the role of serum thyroid hormones in regulating the bioactivity of TSH.

DESIGN

We determined in vitro TSH bioactivity and glycosylation in nine patients (six females and three males, age 41.3 yr) with primary hypothyroidism before and after L-T(4) replacement, in 11 age- and sex-comparable controls (seven females and four males, age 37.6 yr), and in two thyroidectomized patients with TSH-secreting adenomas during and after L-T(4) withdrawal.

METHODS

In vitro TSH bioactivity was measured by a sensitive and specific bioassay based on cAMP generation by Chinese hamster ovary cells transfected with human TSH receptor. TSH glycosylation was assessed by concanavalin A lectin and ricin column affinity chromatography.

RESULTS

In vitro TSH bioactivity in hypothyroid patients was low as compared with controls (0.48 +/- 0.1 vs. 1.1 +/- 0.2; P = 0.004) and increased during L-T(4) (0.48 +/- 0.1 vs. 0.8 +/- 0.1; P = 0.01). A strong significant correlation (r = +0.80; P = 0.004, Spearman) was observed between the absolute increments of serum TSH bioactivity and T(3) during L-T(4) replacement. The degree of sialylation was elevated in hypothyroid patients before treatment (47 +/- 2.4% vs. 29 +/- 4.3%; P = 0.002) and decreased significantly after L-T(4) (47 +/- 2.4% vs. 33 +/- 4.3%; P = 0.02). The mannose content of serum TSH in hypothyroid patients was similar to controls and did not change during L-T(4). In vitro TSH bioactivity also decreased in patients with TSH-secreting adenomas during L-T(4) withdrawal.

CONCLUSION

These data indicate that serum thyroid hormone level is a positive regulator of TSH bioactivity.

Carbohydrate complexity and proportions of serum FSH isoforms in the male: lectin-based studies

FSH is synthesized and secreted in multiple molecular forms with different oligosaccharide structures which are needed for full expression of biological activity. GnRH and sex steroids modulate oligosaccharide structure and composition. In the present study we have assessed the carbohydrate complexity and proportion of circulating FSH isoforms during puberty, aging and after androgen administration to pubertal anorchid boys. Preparative isoelectrofocusing and lectin chromatography were used to isolate FSH isoforms on the basis of charge and internal carbohydrate complexity. Differences in sialic acid content and a progressive increase of isoforms bearing highly branched oligosaccharides were found during puberty. Less acidic, more bioactive FSH isoforms, secreted at mid-puberty may modulate important maturational events in the Sertoli cell population. Androgen administration to pubertal anorchid boys favoured the secretion of this type of isoforms. In adult men, the predominance of FSH isoforms bearing complex type oligosaccharides remained unchanged until very advanced age. These results show that the predominance of FSH isoforms bearing fully processed oligosaccharides in circulation may contribute to the development and maintenance of seminiferous epithelium function in men.

The endocrine system and ageing

Complex changes occur within the endocrine system of ageing individuals. This article explores the changes that occur in the metabolism and production of various hormones and discusses the resulting clinical consequences. As individuals age there is a decline in the peripheral levels of oestrogen and testosterone, with an increase in luteinizing hormone, follicle-stimulating hormone and sex hormone-binding globulin. Additionally there is a decline in serum concentrations of growth hormone, insulin-like growth factor-I and dehydroepiandrosterone and its sulphate-bound form. Even though there are complex changes within the hypothalmo-pituitary-adrenal/thyroid axis, there is minimal change in adrenal and thyroid function with ageing. The clinical significance of these deficiencies with age are variable and include reduced protein synthesis, decrease in lean body mass and bone mass, increased fat mass, insulin resistance, higher cardiovascular disease risk, increase in vasomotor symptoms, fatigue, depression, anaemia, poor libido, erectile deficiency and a decline in immune function. For each endocrine system, studies have been carried out in an attempt to reverse the effects of ageing by altering the serum hormonal levels of older individuals. However, the real benefits of hormonal treatment in older individuals are still being evaluated.

Age related variation of salivary testosterone values in healthy Japanese males

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

An ensemble model of the male gonadal axis: illustrative application in aging men

Testosterone (Te) production declines in the aging male, albeit for unknown reasons. Plausible mechanisms include reduced secretion of GnRH, less feedforward by LH, and/or altered feedback by systemic Te. The present study tests all three postulates in a cohort of 10 young (20-35 yr old) and eight older (50-72 yr old) men. The experimental paradigm comprised graded blockade of the GnRH receptor to create four distinct strata of LH and Te pulsatility in each subject. A novel analytical formalism was developed to reconstruct implicit dose-response functions linking 1) virtual GnRH outflow positively to LH secretion, 2) LH pulses positively to Te secretion, and 3) Te concentrations negatively to the size and number of LH secretory bursts. Validation was by direct pituitary sampling in the horse and sheep. Statistical comparisons disclosed that age decreased the efficacy of each of 1) virtual GnRH outflow (P < 0.01), 2) LH drive of Te secretion (P < 0.01), and 3) total, bioavailable and free Te feedback on GnRH-driven LH secretion (P = 0.015). In contrast, age increased the potency of virtual GnRH feedforward (P = 0.013) and did not affect Te's inhibition of LH pulse frequency. Unexplained variance was less than 10%. Robustness was shown by resampling techniques. Accordingly, competitive silencing of one locus of control and ensemble-based analyses identified triple regulatory deficits in the aging male gonadal axis. The generality of the present integrative model suggests utility in parsing interlinked adaptations in other physiological networks.

Is there a need for recombinant human luteinizing hormone (lutropin alfa) supplementation in ovarian stimulation for assisted reproduction?

Luteinizing hormone is now available as the recombinant product, lutropin alfa for the treatment of female infertility. It is necessary in the natural process of follicular growth and maturation. It is not yet clear which patients really benefit from the addition of this medication to conventional gonadotropin stimulation procedures in infertility treatment. Certainly, it has a proven benefit in patients suffering from hypogonadotropic hypogonadism (WHO I). Others may be older patients, patients with a profound gonadotropin suppression stimulated in long gonadotropin-releasing hormone agonist protocols, or patients with poor ovarian response to conventional stimulation strategies. The available data are reviewed herein.

Exploiting LH in ovarian stimulation

During intermediate-late phases of human folliculogenesis, LH plays a key role in promoting steroidogenesis and growth of the leading follicle. Ovarian stimulation for assisted reproduction techniques usually consists of administering exogenous FSH in a low LH environment. Although an impairment in LH-dependent paracrine activities would be expected, multiple follicular growth is efficiently achieved in almost all patients. Thus, there appears to be a discrepancy between classical folliculogenesis models and data from IVF. This study examines the 'interface' between basic endocrinological and clinical evidence, in an attempt to answer two questions: is there an LH therapeutic window, and if there is, how can this be exploited in the practice of assisted reproduction? It also reviews the evidence that specific subgroups of women may benefit from LH supplementation during ovarian stimulation.

Clomiphene citrate effects on testosterone/estrogen ratio in male hypogonadism

AIM

Symptomatic late-onset hypogonadism is associated not only with a decline in serum testosterone, but also with a rise in serum estradiol. These endocrine changes negatively affect libido, sexual function, mood, behavior, lean body mass, and bone density. Currently, the most common treatment is exogenous testosterone therapy. This treatment can be associated with skin irritation, gynecomastia, nipple tenderness, testicular atrophy, and decline in sperm counts. In this study we investigated the efficacy of clomiphene citrate in the treatment of hypogonadism with the objectives of raising endogenous serum testosterone (T) and improving the testosterone/estrogen (T/E) ratio.

METHODS

Our cohort consisted of 36 Caucasian men with hypogonadism defined as serum testosterone level less than 300 ng/dL. Each patient was treated with a daily dose of 25 mg clomiphene citrate and followed prospectively. Analysis of baseline and follow-up serum levels of testosterone and estradiol levels were performed.

RESULTS

The mean age was 39 years, and the mean pretreatment testosterone and estrogen levels were 247.6 +/- 39.8 ng/dL and 32.3 +/- 10.9, respectively. By the first follow-up visit (4-6 weeks), the mean testosterone level rose to 610.0 +/- 178.6 ng/dL (P < 0.00001). Moreover, the T/E ratio improved from 8.7 to 14.2 (P < 0.001). There were no side effects reported by the patients.

CONCLUSIONS

Low dose clomiphene citrate is effective in elevating serum testosterone levels and improving the testosterone/estradiol ratio in men with hypogonadism. This therapy represents an alternative to testosterone therapy by stimulating the endogenous androgen production pathway.

Who needs LH in ovarian stimulation?

LH plays a key role in the intermediate-late phases of folliculogenesis. Although ovarian stimulation is efficiently achieved in most cases by the administration of exogenous FSH alone, specific subgroups of women may benefit from LH activity supplementation during ovarian stimulation. Some authors have found improved outcome with LH activity supplementation in advanced reproductive age women. Experience suggests that in about 10-12% of young normogonadotrophic patients treated with a gonadotrophin-releasing hormone agonist (GnRH-a) long protocol plus recombinant FSH human (r-hFSH), a 'steady response' is observed. In this subgroup of women, a higher number of oocytes is retrieved when daily LH activity supplementation is given from stimulation day 8, if compared with the standard FSH dose increase. Another subgroup of patients who may benefit from LH activity supplementation are those at risk for poor ovarian response treated with GnRH antagonist. Recent data demonstrate that in these women, when GnRH is administered in a flexible protocol, the concomitant addition of recombinant human LH improves the number of mature oocytes retrieved, when compared with the standard GnRH-a flare-up protocol. Thus, well calibrated LH administration improves the ovarian outcome in patients >35 years, in those showing an initial abnormal ovarian response to r-hFSH monotherapy, and in 'low prognosis' women treated with GnRH antagonists.

Aging in healthy men impairs recombinant human luteinizing hormone (LH)-stimulated testosterone secretion monitored under a two-day intravenous pulsatile LH clamp

CONTEXT

Testosterone (Te) depletion in aging men in principle could reflect deficits in the hypothalamus, pituitary gland, or testis. Available pharmacological studies of possible failure of Leydig cell steroidogenesis remain inconclusive.

OBJECTIVE

The objective of the study was to assess Te secretion in older and young men in response to near physiological LH stimulation.

INTERVENTION

Pulsatile i.v. infusion of recombinant human LH was administered for 2 d to stimulate Te secretion during suppression of endogenous LH concentrations with a potent selective GnRH receptor antagonist (ganirelix). SUBJECTS/CONTEXT: Healthy older (aged 60-73 yr, n = 8) and young (19-30 yr, n = 13) men were studied in an academic setting.

MEASURES

Pulsatile LH and Te concentrations on the second day of exogenous LH stimulation were measured.

RESULTS

Serum ganirelix concentrations and infused LH pulse increments were similar by age. In contrast, older subjects manifested: 1) reduced mean Te concentrations (P = 0.016), Te peak heights (P = 0.014), increments (P = 0.010), summed areas (P < 0.013), and interpeak Te concentrations (P = 0.023); 2) decreased Te to LH concentration ratios (P = 0.002); 3) diminished LH-Te feed-forward synchrony (P = 0.020); and 4) a blunted amplitude (P = 0.036) and advanced phase (P = 0.013) of diurnal Te rhythms.

CONCLUSION

A novel regimen of pulsatile LH stimulation for 48 h during GnRH receptor blockade unmasks deficits in pulsatile, basal, synchronous, and nyctohemeral Te secretion in healthy older men. These findings do not exclude concomitant defects in GnRH outflow and/or Te-negative feedback in the aging male.

Arrested germ cell divisions in the ageing human testis

Arrested divisions represent a defective type of germ cell division. The cells are irreversibly arrested in a state marked by strongly condensed chromosomes, a dissolved nuclear envelope and a disturbed spindle apparatus. They finally die. The present ultrastructural study of the ageing human seminiferous epithelium is the first to describe such cells in the human testis. The cells usually lie in small groups and show intercellular bridges connecting them. The bridges lack a bridge-partitioning complex, a structure otherwise characteristic for bridges between dividing germ cells of a clone. Frequently, arrested divisions show signs of cytoplasmic disorganization and severe structural degradation. Centrioles, irregular microtubules, small membranous vesicles and granular electron-dense material are crowded within the circle of chromosomes. Some cells show numerous small vesicles and larger membranous structures distributed throughout the cytoplasm. The presence of arrested germ cell divisions in ageing men might be connected with local dysfunctions of the Sertoli cell barrier, which are known to appear focally in the ageing human seminiferous epithelium as well.

Short-term aromatase-enzyme blockade unmasks impaired feedback adaptations in luteinizing hormone and testosterone secretion in older men

The mechanisms subserving hypoandrogenemia and relative hypogonadotropism in older men are not known. The present study tests the clinical hypothesis that aging impairs hypothalamopituitary adaptations to feedback withdrawal induced by antagonism of estrogen biosynthesis. To this end, we appraised gonadal axis responses to estrogen depletion induced by anastrozole (a potent and selective aromatase inhibitor) in nine older and 11 young men vs. placebo in 17 other older and eight young men. The study design comprised a prospectively randomized, double-blind, parallel-cohort intervention. To monitor LH release, blood was sampled every 10 min for 24 h; LH concentrations were assayed by two-site monoclonal immunoradiometric assay; pulsatile LH release quantitated by a model-free discrete peak-detection technique (Cluster); feedback-dependent orderliness of LH secretion via the approximate entropy statistic; and 24-h rhythmicity of LH concentrations by cosine analysis. At baseline, older men had comparable estradiol and testosterone but lower LH concentrations than young controls. Exposure to anastrozole reduced (24-h pooled) serum estradiol concentrations by 50% (P < 0.001) and elevated mean LH concentrations by 2.1-fold (P < 0.001) in both the young and older cohorts. However, older men failed to achieve young adult augmentation of the following: 1) total testosterone concentrations (P < 0.01) or molar testosterone to SHBG ratios (P < 0.01); 2) incremental LH pulse amplitude (P < 0.001) and LH peak area (P < 0.01); 3) mean LH pulse frequency (P = 0.0044); and 4) quantifiable irregularity (approximate entropy) of LH release patterns (P < 0.001). FSH concentrations became comparable in the two age cohorts. In summary, administration of a potent and selective aromatase antagonist reduces estradiol and elevates mean LH concentrations equivalently in young and older men. The low estrogen-feedback state in elderly men unmasks diminished incremental LH pulse amplitude and area; absence of further acceleration of LH pulse frequency; impaired regulation of the orderliness of LH release; and reduced testosterone to SHBG ratios. Thus, aging alters expected hypothalamopituitary-gonadal adaptations to short-term partial estrogen depletion in healthy men.

Recombinant human LH supplementation versus recombinant human FSH (rFSH) step-up protocol during controlled ovarian stimulation in normogonadotrophic women with initial inadequate ovarian response to rFSH. A multicentre, prospective, randomized controlled trial

BACKGROUND

In approximately 12-14% of young normogonadotrophic women treated with a depot GnRH agonist long protocol, the initial ovarian response to recombinant human FSH (rFSH) can be suboptimal. We have tested the hypothesis that these women may benefit from recombinant human LH (rLH) supplementation in a multicentre, prospective, randomized trial compared with patients treated with an rFSH step-up protocol.

METHODS

A total of 260 young normogonadotrophic women undergoing controlled ovarian stimulation with a GnRH agonist long protocol for IVF/ICSI were enrolled. The starting dose of rFSH was 225 IU. One hundred and thirty patients with serum estradiol levels <180 pg/ml and with at least six follicles with a mean diameter >5 mm but none >10 mm on both day 5 and day 8 of stimulation were randomly allocated to two groups. From the eighth day of stimulation, women in group A (n=65) received 150 IU of rLH in addition to rFSH, while those in group B (n=65) had an increase of 150 IU in the daily dose of rFSH (step-up protocol). One hundred and thirty normally responding women continued monotherapy with rFSH and served as a further control population (group C).

RESULTS

The mean number of cumulus-oocyte complexes retrieved in group A (9.0+/-4.3) was significantly higher (P<0.01) compared with group B (rFSH 6.1+/-2.6) but significantly lower compared with group C (10.49+/-3.7, P<0.05). Implantation and pregnancy rates were significantly lower (P<0.05) in the rFSH step-up group (10.5 and 29.3% respectively) when compared with normal responders (18.1 and 47.3% respectively).

CONCLUSIONS

rLH supplementation is more effective than increasing the dose of rFSH in terms of ovarian outcome in patients with an initial inadequate ovarian response to rFSH alone.

Erosion of endogenous testosterone-driven negative feedback on pulsatile luteinizing hormone secretion in healthy aging men

The present study tests the intuition that successful aging in men is marked by: 1) impaired feedforward by endogenous LH concentrations (con) of testosterone (Te) secretion (sec); and/or 2) attenuated feedback by unmanipulated Te con of LH sec. The goal was to assess both implicit linkages analytically without disrupting normal pathway coupling. This strategy required: 1) assay of paired LH and Te con sampled every 10 min for 24 h in 13 older (O) (ages 60-78 yr) and 13 young (Y) (ages 18-30 yr) men; 2) deconvolution-based estimation of LH and Te sec rates; 3) lag-specific cross-correlation analyses of the relationships between LH and Te con and sec; and 4) statistical contrasts by age stratum. Salient outcomes were: 1) O and Y men maintain comparable LH con drive of Te sec, viz maximal r = +0.51 and r = +0.52, respectively, at an optimal time lag of 50 min (both P < 0.001 against random LH and Te associations); 2) elderly subjects exhibit reduced Te con inhibition of LH sec [minimal r = -0.008 (O) vs. r = -0.10 (Y), P < 0.01 at a time lag of 40 min]; 3) mean (24-h) LH con do not differ by age; and 4) molar Te/sex hormone-binding globulin con are lower in the elderly than in Y individuals (P < 0.01).In conclusion, noninvasive analyses predict that attenuation of endogenous Te feedback restraint on the hypothalamo-pituitary unit may be an early biological marker of adaptive changes in the GnRH-LH-Te ensemble axis in the healthy O male.

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).

Age and gender effects on serotonin-dependent plasticity in respiratory motor control

We review recent evidence indicating that serotonin-dependent plasticity in respiratory control is influenced by age and gender. Specifically, respiratory long-term-facilitation following intermittent hypoxia decreases with age in male rats, but increases in female rats. We speculate about a possible relationship between age and gender effects on serotonin-dependent plasticity in upper airway motoneuron pools and the prevalence of obstructive sleep apnea.

Recent neuroendocrine facets of male reproductive aging

We recently identified consistent attenuation of LH and testosterone secretory pulse amplitude and associated disruption of their orderly patterns of release in healthy older men. These dynamic changes emerge despite young-adult concentrations of LH and total testosterone. Moreover, we could document disruption of synchrony between LH secretion and oscillations in FSH, prolactin, sleep-stage and NPT (nocturnal penile tumescence), thus pointing to loss of coordinate neurohormone outflow. Such data suggest that CNS-hypothalamically based regulatory defects may be important in aging, as inferred indirectly in the old male rat and mouse more than 15 years ago. How such alterations are related to specific hypothalamic neurotransmitter changes in aging will be critical to unravel.

Androgen actions on central serotonin neurotransmission: relevance for mood, mental state and memory

Sex steroids exert potent effects on mood and mental state in the human. Our previous experimental findings in female rats suggest that these effects may be mediated, in part, by the action of estrogen on the 5-hydroxytryptamine2A receptor (5-HT(2A)R) and serotonin transporter (SERT) in brain. Here we review our recent findings on the effect of acute (approximately 32 h) testosterone manipulation on central 5-HT(2A)R and SERT in male rats. Castration decreased while testosterone or estrogen, but not 5alpha-dihydrotestosterone (5alpha-DHT), increased significantly the content of 5-HT(2A)R mRNA and SERT mRNA in the dorsal raphe nucleus (DR) and the density of 5-HT(2A)R and SERT binding sites in higher centers of the brain. The lack of effect of 5alpha-DHT, a potent androgen which cannot be converted to estrogen, suggests that the action of testosterone depends upon its conversion to estrogen by aromatase. This may also explain why estrogen, but not testosterone or 5alpha-DHT, increased the density of 5-HT(2A)R binding sites in the caudate-putamen, a brain region where aromatase is scarce. The estrogen induction of SERT mRNA is most prominent in the rostral DR and this together with the correlation between sensitivity of DR serotonin neurons to estrogen and neurotoxic amphetamine derivatives provides a potential topochemical handle with which to investigate testosterone/estrogen regulation of SERT gene expression. These findings are discussed in relation to the possible role of interactions between sex steroids and serotonin mechanisms in mood disorders, schizophrenia and Alzheimer's disease.

Hormonal and biochemical parameters in the determination of osteoporosis in elderly men

The extent to which changes in several hormonal and biochemical parameters are involved in the pathogenesis of osteoporosis in men remains controversial. This study examined the roles of free testosterone (T), estradiol (E2), sex hormone-binding globulin (SHBG), 25-hydroxyvitamin D, PTH, and insulin-like growth factor I in the determination of bone mineral density (BMD) in 437 community-dwelling elderly men. Age, height, weight, quadriceps strength, and femoral neck (FN) and lumbar spine (LS) BMD were also obtained. In multiple regression analysis, after adjusting for age and weight, low E2 (P = 0.01), and high SHBG (P = 0.0002) levels were common determinants of FN and LS BMD. In addition, high PTH (P = 0.03) was an independent predictor of FN BMD, and low free T (P = 0.02) was an independent predictor of LS BMD. Low free T was associated with FN BMD in univariate analysis only. The hormonal measurements collectively accounted for 5% and 7% of the age- and weight-adjusted variance of FN and LS BMD, respectively. The sex steroids, SHBG and insulin-like growth-I were found to be interrelated using a technique of path analysis that examines the intercorrelation between these variables. A subject with any one abnormal serum parameter had a 4-fold increase in the risk of osteoporosis, whereas three abnormal parameters were associated with an 11-fold increased risk, although the latter group only applied to 1% of the study population. Although the precise causal effects these biochemical parameters may have on the development of osteoporosis remains to be determined, the present findings support an important interrelated role for these hormonal and biochemical parameters on changes in bone density in elderly men.

The effects of age and spontaneous adenoma formation on trophic activity in the rat pituitary gland: a comparison with trophic activity in the human pituitary and in human pituitary adenomas

The effects of ageing on trophic activity in the pituitary gland and the molecular events that underlie pituitary tumour formation are poorly understood. In the present study we have used an extremely accurate system to analyse trophic activity in human pituitary tumours and compared our findings with trophic activity in spontaneous rat pituitary adenomas and with changes in basal rates of turnover as the animals age. Thin, hematoxylin and eosin-stained pituitary sections from groups of male Wistar rats aged 6 weeks to 16 months, killed at 90-min intervals after receiving a single intraperitoneal bolus of colchicine to block cellular passage through mitosis, were evaluated histologically. Extremely accurate quantification of small changes in the prevalence of trophic events, and thus the rate of cell turnover, was achieved using a dedicated computerized aid to manual cell counting. Results were compared with the prevalence of mitotic activity in 24 spontaneous rat pituitary adenomas and with a series of 97 archival human pituitary adenomas and 24 normal human pituitary glands obtained at autopsy. In rats, average basal pituitary cell turnover declined by over 95% between 6 weeks and 16 months of age. Concurrent with this decline was a marked increase in the prevalence of adenoma formation. The prevalence of mitotic activity in spontaneous rat pituitary adenomas averaged almost twice that seen in normal, young rat pituitary and exceeded 16 times that seen in the pituitary of aged animals. In contrast, when compared to normal human pituitary tissue, average trophic activity in human pituitary adenomas remained extremely low.

Serotonin transporter (SERT) mRNA and binding site densities in male rat brain affected by sex steroids

Estrogen increases serotonin transporter (SERT) mRNA and binding sites in female rat brain. In order to determine whether changes in SERT are gender- and steroid-specific we have now carried out studies on adult male Wistar rats which were either intact or castrated (under halothane anesthesia) and injected with arachis oil, estradiol benzoate (EB), testosterone propionate (TP) or the non-aromatizable androgen, 5alpha-dihydrotestosterone (5alpha-DHT). The number of SERT mRNA-expressing cells in the dorsal raphe (DR) nucleus was decreased by castration and increased by treatment (for approximately 32 h) with EB or TP, but not 5alpha-DHT. Sex steroids had no effect on the number of SERT mRNA-expressing cells in the median raphe nucleus. The density of SERT sites, assessed by autoradiography of [3H]paroxetine binding, was significantly reduced in arcuate nucleus and median raphe after castration, and increased in arcuate, basolateral amygdala and ventromedial hypothalamic nucleus by treatment with EB or TP, but not 5alpha-DHT. Estradiol, but not testosterone or 5alpha-DHT reduced the density of SERT sites in midbrain central grey. These data show that testosterone as well as estrogen affects SERT expression in male brain, and that the action of testosterone probably depends upon its enzymatic conversion, by aromatase, to estradiol. Our findings may have implications for sex steroid control of mood and behavior, and the action of neurotoxic derivatives of amphetamine, such as 3, 4-methylenedioxymethamphetamine, in the human.

Endocrine aspects of ageing in the male

There is a statistical decline of testosterone levels in ageing men, most manifest in free testosterone. While this fall is only moderate, ageing men show clinical signs of hypogonadism (loss of muscle mass/strength, reduction in bone mass and an increase in visceral fat). This might represent not only a fall but (also) an impairment of the biological action of androgens in target organs. The first small scale studies of androgen supplement administration in ageing men were not disappointing. Anticipated risks lie with the prostate and the cardiovascular system. The risks with regard to prostate disease are often over-rated. The question remains how the segment of the ageing male population possibly benefiting from androgen supplements, can be identified. For the treatment of postmenopausal women 'designer oestrogens' are being developed; similarly, designer androgens retaining beneficial anabolic effects with elimination of harmful effects on the prostate and cardiovascular system, could be devised.