Photoperiodic variations in plasma concentration of testosterone in the rabbit

The photoperiodic variations of testosterone plasmatic levels in male rabbits have been studied. The animals were subjected to the influence of three circadian rhythms: 12/12, 14/10 and 10/14 h of light/darkness. The hormone assay was carried out using an enzymeimmunoassay method (Competitive ELISA). Blood samples were of two different types: seriated and non-seriated, to find if these might be any differences in the results. It is concluded that testosterone plasmatic levels are within physiologic values (0.3-10.0 ng/ml), although differences depending on the light/darkness cycle and on the type of blood extraction are remarkable; for this reason the selection of the circadian rhythm will depend on the experimentation that is to be carried out.     

Endemic goitre and plasmatic levels of vitamins A and E in the school-children on the island of Krk, Croatia

A total of 1975 school-children on the island of Krk aged 7-19 years of life were included in this study. The purpose was to establish the goitre status and plasmatic level of vitamins A and E in the examined children with the enlarged thyroid gland. The goitre prevalence was 29.8%. The average plasmatic values of vitamins A and E in the children with enlarged thyroids were statistically significantly lower from the reference values. Mentioned goitre prevalence at the level of moderate and heavier endemic goitre speaks on behalf of alimentary iodine deficiency. But the goiter examinations suggested the idoine deficiency not to be the only etiological factor of goitre on the island of Krk. Lower average plasmatic values of vitamins A and E in the examined with the enlarged thyroids referred to this fact to a certain degree.     

D-Asp: a new player in reproductive endocrinology of the amphibian Rana esculenta

We investigated the involvement of D-Aspartic acid (D-Asp) on ovarian and testicular morphology of the green frog, Rana esculenta, and its effect on the testosterone production. The study has been performed throughout the reproductive cycle. In both ovary and testis a substantial amount of D-Asp is endogenously present and its concentration varies as function of reproduction. In the frog, D-Asp content is differently correlated with gonadal and plasmatic levels of testosterone, depending on the sex. In fact, the amount of the D-Asp is inversely linked with that of the testosterone in the ovary, while this correlation directly matched in the testis. In vivo short-term experiments, consisting of a single intra-peritoneal injection of D-Asp (2.0 μmol/g body weight), demonstrated that the enantiomer is significantly accumulated by both the ovary and testis, reaching after 3 h the highest uptake and thereafter decreasing to baseline values within 24 h. Furthermore, D-Asp influences the synthesis and/or the release of testosterone, causing a decrease of its level in the female, and an increase in the male, respectively. In vivo long-term experiments, D-Asp, chronically administered to the frogs of both sexes, enhances the maturation of both gonads, determining in the oocytes an higher accumulation of carbohydrate yolk plates in the ooplasm, and stimulating the spermatogenesis in the testis. Taken altogether, our results show that D-Asp operates differently in female and male frog gonads, indicating that it has different targets in the reproductive machinery depending on the sex.     

Contribution de la testostérone biodisponible aux explorations hormonales pour le diagnostic de l’andropause

The measurement of bioavailable testosterone (BT) is considered to be an essential analytical criterion for the diagnosis of male hypogonadism, but the reported normal values differ from one study to another and no consensus has been reached concerning the cut-off values for the diagnosis of androgen deficiency in aging males. Using the lower values measured in a group of clinically normogonadic men between the ages of 40 and 49 years, we have established our own cut-off values: 8 nmol/L for total testosterone and 3.5 nmol/L for BT. By applying these criteria to a group of 87 men with clinical symptoms of androgen deficiency, androgen deficiency was confirmed by laboratory assays in only 14% of these men based on total testosterone, but in 60% of men based on BT. The inverse correlation between BT and SHBG was confirmed regardless of the total testosterone level. SHBG assay is very useful for the diagnosis of androgen deficiency in a population of older males, but cannot replace direct measurement of BT for an accurate individual diagnosis.     

Testosterone Trajectories and Reference Ranges in a Large Longitudinal Sample of Male Adolescents

Purpose

Pubertal dynamics plays an important role in physical and psychological development of children and adolescents. We aim to provide reference ranges of plasma testosterone in a large longitudinal sample. Furthermore, we describe a measure of testosterone trajectories during adolescence that can be used in future investigations of development.

Methods

We carried out longitudinal measurements of plasma testosterone in 2,216 samples obtained from 513 males (9 to 17 years of age) from the Avon Longitudinal Study of Parents and Children. We used integration of a model fitted to each participant’s testosterone trajectory to calculate a measure of average exposure to testosterone over adolescence. We pooled these data with corresponding values reported in the literature to provide a reference range of testosterone levels in males between the ages of 6 and 19 years.

Results

The average values of total testosterone in the ALSPAC sample range from 0.82 nmol/L (Standard Deviation [SD]: 0.09) at 9 years of age to 16.5 (SD: 2.65) nmol/L at 17 years of age; these values are congruent with other reports in the literature. The average exposure to testosterone is associated with different features of testosterone trajectories such as Peak Testosterone Change, Age at Peak Testosterone Change, and Testosterone at 17 years of age as well as the timing of the growth spurt during puberty.

Conclusions

The average exposure to testosterone is a useful measure for future investigations using testosterone trajectories to examine pubertal dynamics.     

Effects of aproteic diet on hypothalamic-pituitary- gonadal regulation in the male rat

The effect of an aproteic diet (Ap) on the reproductive axis in young male rats was studied. Also the refeeding effect at different times after the aproteic diet was studied. The Ap diet was given during 21 days. In refeeding groups, the control diet was given during 2, 4 and 6 weeks after the aproteic diet. We studied the plasmatic testosterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels. Also the hypothalamic GnRH concentration and in vitro hypothalamic GnRH secretion in basal and induced condition was studied. The total protein deficit produced significant reduction in body, testis, seminal vesicles and prostate weights. This was accompanied with decreased levels of plasmatic testosterone (P<0.02). In this aproteic group there was a significant reduction in LH (P<0.05) and FSH (P<0.05) plasmatic levels. Refeeding with control diet reversed this situation, producing significant increment in LH (P<0.05) and FSH levels (P<0.01) at the fourth and second weeks, respectively. The basal hypothalamic GnRH secretion did not differ from the control; nevertheless the induced secretion was significantly (P<0.05) greater in the aproteic group. Also the hypothalamic GnRH concentration was increased (P<0.05) in animals fed with the aproteic diet. The minor testis, prostate, and seminal vesicles" weight, and a decreased plasmatic testosterone in rats fed with an aproteic diet, are produced by a decrease in gonadotrophin secretion. This decrease in turn is caused by a reduction in GnRH secretion, since hypothalamic GnRH concentration is increased in rats fed with the aproteic group, and induced secretion is greater in this group. All these alterations produced by an aproteic diet are reversible, since-with contol diet refeeding-the gonadotrophin secretion returned at control levels.     

Thymosin fails to reconstitute normal estradiol levels into neonatally thymectomized rats

Neonatal thymectomy into female rats reduced estradiol plasmatic levels during the first 60 days. This disturbance was not corrected by thymosin opotherapy. Comparison with male rats and testosterone disturbance was discussed.     

Microgravity effect on testicular functions

In mammals spaceflight influences spermatogenesis since spermatogonial germ cell proliferation, compared to synchronous controls, is lightly decreased in irradiated or flown rats. Moreover, changes of the plasmatic testosterone production was described either in flight rats, or in rats maintained in simulated microgravity conditions. The hormonal levels of the astronauts change as it has been previously described, including hormones involved in the regulation of spermatogenesis such as testosterone and luteinizing hormone (LH). In microgravity conditions, human testosterone levels decreased whereas circulating LH levels increased. To study the effect of simulated microgravity on mammalian spermatogenesis we have utilized the Rotary Cell Culture System (RCCS) and we have cultured testicular fragments isolated from prepuberal rats in a chemically defined medium for three days under microgravity conditions. As control we have cultured the same amount of fragments at unit gravity. The morphology of the samples has been studied and the number of proliferating cells has been counted in control samples and in samples maintained in RCCS. The results indicate that the number of duplicating cells in the tubules was significantly increased in the microgravity-cultured fragments. The amount of testosterone secreted in the culture medium has been also evaluated and in RCCS samples the amount of the hormone was higher respect to the control samples.     

Induction of maternal behavior and some hormonal and physiological correlates in the domestic hen

The manifestation of maternal behavior and the variations of plasmatic levels of gonadic hormones (testosterone, delta 4-androstenedione, and 17 beta-estradiol) have been studied in two groups of domestic hens (layers and nonlayers) during a forced adoption experiment. Maternal behavior appears later in actively laying hens than in nonlayers. The former hens show a higher level of androgens (T and delta 4). The appearance of typical maternal behavior coincides with a pause in laying and a decrease in all the plasmatic steroid levels measured.     

Membrane mechanisms of testosterone action]

The experiments on adult Wistar rats have shown that testosterone administration provoke hyperpolarization of hepatocytes and adrenocorticocytes plasmatic membranes. It was discovered that this hyperpolarization was caused by cell Na, K-ATPase activation. Inhibitors of protein biosynthesis prevent both testosterone-induced hyperpolarization and Na, K-ATPase activation. It is shown that some hyperpolarization factor appeared in the cytosol and blood serum under testosterone influence. It was suggested that this mechanism is mediated by cell genome.     

Testosterone and Androgen Receptor Sensitivity in Relation to Hyperactivity Symptoms in Boys with Autism Spectrum Disorders

Introduction

Autism spectrum disorders (ASD) and hyperactivity symptoms exhibit an incidence that is male-biased. Thus androgen activity can be considered a plausible biological risk factor for these disorders. However, there is insufficient information about the association between increased androgen activity and hyperactivity symptoms in children with ASD.

Methods

In the present study, the relationship between parameters of androgenicity (plasmatic testosterone levels and androgen receptor sensitivity) and hyperactivity in 60 boys (age 3–15) with ASD is investigated. Given well documented differences in parent and trained examiners ratings of symptom severity, we employed a standardized parent`s questionnaire (Nisonger Child Behavior Rating Form) as well as a direct examiner`s rating (Autism diagnostic observation schedule) for assessment of hyperactivity symptoms.

Results

Although it was found there was no significant association between actual plasmatic testosterone levels and hyperactivity symptoms, the number of CAG triplets was significantly negatively correlated with hyperactivity symptoms (R² = 0.118, p = 0.007) in the sample, indicating increased androgen receptor sensitivity in association with hyperactivity symptoms. Direct trained examiner´s assessment appeared to be a relevant method for evaluating of behavioral problems in the investigation of biological underpinnings of these problems in our study.

Conclusions

A potential ASD subtype characterized by increased rates of hyperactivity symptoms might have distinct etiopathogenesis and require a specific behavioral and pharmacological approach. We propose an increase of androgen receptor sensitivity as a biomarker for a specific ASD subtype accompanied with hyperactivity symptoms. Findings are discussed in terms of their implications for practice and future research.     

Testosterone related to age and life-history stages in male baboons and geladas

Despite significant advances in our knowledge of how testosterone mediates life-history trade-offs, this research has primarily focused on seasonal taxa. We know comparatively little about the relationship between testosterone and life-history stages for non-seasonally breeding species. Here we examine testosterone profiles across the life span of males from three non-seasonally breeding primates: yellow baboons (Papio cynocephalus or P. hamadryas cynocephalus), chacma baboons (Papio ursinus or P. h. ursinus), and geladas (Theropithecus gelada). First, we predict that testosterone profiles will track the reproductive profiles of each taxon across their respective breeding years. Second, we evaluate age-related changes in testosterone to determine whether several life-history transitions are associated with these changes. Subjects include males (> 2.5 years) from wild populations of each taxon from whom we had fecal samples for hormone determination. Although testosterone profiles across taxa were broadly similar, considerable variability was found in the timing of two major changes: (1) the attainment of adult levels of testosterone and (2) the decline in testosterone after the period of maximum production. Attainment of adult testosterone levels was delayed by 1 year in chacmas compared with yellows and geladas. With respect to the decline in testosterone, geladas and chacmas exhibited a significant drop after 3 years of maximum production, while yellows declined so gradually that no significant annual drop was ever detected. For both yellows and chacmas, increases in testosterone production preceded elevations in social dominance rank. We discuss these differences in the context of ecological and behavioral differences exhibited by these taxa.     

A Validated Age-Related Normative Model for Male Total Testosterone Shows Increasing Variance but No Decline after Age 40 Years

The diagnosis of hypogonadism in human males includes identification of low serum testosterone levels, and hence there is an underlying assumption that normal ranges of testosterone for the healthy population are known for all ages. However, to our knowledge, no such reference model exists in the literature, and hence the availability of an applicable biochemical reference range would be helpful for the clinical assessment of hypogonadal men. In this study, using model selection and validation analysis of data identified and extracted from thirteen studies, we derive and validate a normative model of total testosterone across the lifespan in healthy men. We show that total testosterone peaks [mean (2.5–97.5 percentile)] at 15.4 (7.2–31.1) nmol/L at an average age of 19 years, and falls in the average case [mean (2.5–97.5 percentile)] to 13.0 (6.6–25.3) nmol/L by age 40 years, but we find no evidence for a further fall in mean total testosterone with increasing age through to old age. However we do show that there is an increased variation in total testosterone levels with advancing age after age 40 years. This model provides the age related reference ranges needed to support research and clinical decision making in males who have symptoms that may be due to hypogonadism.     

Comparison between sex and age class on some physiological, thermal, and hematological indices of the cerrado's marmoset (Callithrix penicillata)

There are few papers about physiological indices in Callithrix penicillata, an increasing primate model in biomedicine. We investigated levels of plasmatic cortisol, plasmatic glucose, free fatty acids, blood cells, tympanic temperature, rectal temperature in C. penicllata, under a fast restraint. Measures of body and weight were accomplished. Males and females were not different regarding any measurements. Body measurements indicated differences between adults and juveniles. Adults showed higher hematocrit and a tendency for higher free fatty acids than juveniles. Right tympanic temperature was higher in adults than juveniles. This result suggests a higher reaction metabolism in adults than juveniles under a restraint stress. Due to the short-time of collecting the data, plasmatic cortisol did not influence physiological parameters. Therefore, we suggest that present results could be considered referential values of C. penicillata physiology.     

Plasmatic protein values in captive adult Iberian red deer stags (<Emphasis Type="Italic">Cervus elaphus hispanicus</Emphasis>)

The aim of this study was to assess the time trend of plasmatic proteins in red deer stags. Blood samples were taken monthly from 17 male red deer for 22 months. Total plasmatic determination and protein electrophoresis were performed. Plasmatic proteins showed minimum values during spring and summer and a maximum at the peak of the mating period. Total globulins, β and γ, followed a pattern similar to that observed for total proteins, whereas α1 and α2 globulins showed no seasonal variations. Albumin showed higher values in early spring and summer and lower values at the beginning of autumn, coinciding with the mating season. These seasonal changes in plasmatic proteins should be taken into account when assessing blood protein analysis results.     

Fitness consequences of increased testosterone levels in female spotless starlings

The role of testosterone in female fitness is poorly known in most vertebrates. It has been proposed that the dynamics of female testosterone may represent a correlated response to selection acting on male testosterone. However, several costs and benefits of enhancing the circulating levels of testosterone in females have been documented in a number of species, suggesting that female testosterone may be the product of direct selection. Despite this, no study has tried to quantify the long-term fitness consequences of manipulating female testosterone. We report the results of an experiment in which we implanted females with testosterone (T-females) and recorded the consequences of this manipulation on investment and reproductive success throughout their lifetime in relation to control females (C-females). Our results show that T-females bred more years in the colony than C-females. The onset of laying was delayed in T-females compared with C-females, but this effect decreased in the years following manipulation. The T-females laid fewer eggs per year, but eggs were heavier than those laid by C-females. The T-females fed nestlings at a lower rate than C-females in the 3 years in which feeding rates were measured and raised fewer fledglings than C-females in the manipulation year. However, since T-females accomplished more breeding attempts than C-females, as a result of their longer stay in the colony, there were no significant differences between the lifetime reproductive success of T- and C-females. There were no overall differences in body size of nestlings raised by T- and C-females, but the body mass of fledglings reached a peak 2-3 years after manipulation for C-females, a tendency not recorded in offspring of T-females. Also, young that were fledged in broods of C-females tended to recruit into the study colony more frequently than those fledged in T-females' nests. All these results indicate that our testosterone manipulation improved the ability of females to acquire and maintain a breeding site but interfered with their reproductive biology and parental investment. Thus, our main conclusion is that under the ecological conditions of our experiment, the addition of exogenous testosterone reduced female fitness. However, differences in population density and female-female competition are likely to alter the fitness landscape of this trait and change the adaptiveness of increased testosterone as a component of female reproductive strategies.     

Effect of ACTH, dexamethasone, and adrenalectomy on the secretion of testosterone in the rat

The effect of ACTH (100 micrograms/animal/day, i.p.), dexamethasone (75 micrograms/animal/day, s.c.), both for three consecutive days, and adrenalectomy, with or without dexamethasone, maintained according to the group, one, two or three days, on the plasmatic testosterone and corticosterone levels, has been studied in adult male Wistar rats. ACTH and adrenalectomy produced a high decrease in testosterone levels (p less than 0.001 for the three days studied). Dexamethasone produced lower testosterone levels in the first day followed by partial recuperation between the second and the third days of its administration. Dexamethasone produced the effects mentioned for intact animals. The changes in corticosterone levels were according to an adequate response of the hypothalamus-pituitary-adrenal system under these experimental circumstances. ACTH exerts an inhibitory effect on testosterone secretion in the rat, so that such an effect from the data obtained after adrenalectomy and simultaneous dexamethasone injections, does not seems to be mediated either by the presence of adrenals or high corticosterone levels.     

Mixed gonadal dysgenesis and precocious puberty

A girl aged 5 years and 6 months presented with premature thelarche in our outpatient clinic. During long-term observation, we recorded growth acceleration, advanced bone age, and elevated oestradiol levels which together were taken to confirm the diagnosis of precocious puberty. The patient was successfully treated with a gonadotropin-releasing hormone agonist, but in view of the poor growth prognosis, recombinant human growth hormone was administered concurrently. At the age of 9 years and 6 months a mild clitoris enlargement and conspicuous muscle development without any further signs of virilization were noticed. Laboratory findings showed high values for testosterone and normal basal values for 17-hydroxyprogesterone and dehydroepinadrosterone sulphate. Explorative laparotomy revealed a gonadoblastoma arising from testicular structures on the left, a female streak gonad on the right side, and normal uterus and fallopian tubes. The karyotype was 46,XY/45,X. These findings confirmed the diagnosis of mixed gonadal dysgenesis with testosterone-producing gonadoblastoma.     

Relationship between the release of hypophyseal LH under the influence of LRH and the plasma testosterone level in women]

There is a direct significant correlation (r = 0,49, p less than 0,01) between cumulative LH response to i.v. injection of 25 mug LRH and testosterone blood level in 17 women with an excess of endogenous androgens (plasmatic testosterone and/or urinary androsterone and etiocholanolone). The relation also exists if the patients are divided in two groups according to the origin of the dysfunction: polycystic ovaries (n = 9, r = 0,62, p less than 0.05) or hypercorticism (n = 8, r = 0,53, p less than 0.1). In the same patients there is no correlation between LH release and the sum of androsterone and etiocholanolone 24 hours urinary excretion (r = 0,21, p: NS); there is no correlation between basal testosterone blood levels and urinary metabolites (r = 0,19, p: NS). Our data suggest that testosterone (or a closely related metabolite) acts at the hypophyseal level to inhibit the spontaneous LH discharge hence increasing the pituitary hormonal stores. This action could be responsible for menstrual abnormalities often found in hirsut women.     

Testosterone stimulates the expression of a social color signal in Yarrow's Spiny Lizard, Sceloporus jarrovii

The sex steroid testosterone has been shown to regulate the development of male-specific coloration in many organisms that exhibit sexual dichromatism, but the role of testosterone is less certain for species in which both sexes express bright coloration. Lizards in the genus Sceloporus possess bright blue patches on their throats and abdomens. These patches, which are used in social signaling, are often regulated by testosterone and are consequently expressed only in males of most species. However, Yarrow's Spiny Lizard (Sceloporus jarrovii, Cope 1875) exhibits a derived condition in which both sexes express bright blue ventral patches despite dramatic sexual differences in circulating testosterone levels throughout postnatal ontogeny. In this study, we used surgical castration and hormone replacement in juvenile males to test the hypothesis that testosterone stimulates the expression of blue ventral coloration in S. jarrovii. In two separate experiments conducted in captivity and the natural field environment, we found that surgical castration decreased the hue and saturation while increasing the brightness of blue throat and abdominal patches. Castration also decreased the amount of black pigment bordering the blue throat patch. Treatment of castrated males with exogenous testosterone restored all aspects of ventral coloration to values similar to those of intact control males. Early organizational effects of testosterone during prenatal development may lead to the expression of blue coloration in both sexes, but the results of our present experiments indicate that subsequent effects of testosterone during sexual maturation further enhance the coloration of males.