Variation In Androgen Levels Research Articles

Steroid hormones as a non-lethal assessment of the reproductive biology in male and female blacktip reef sharks

IntroductionOverexploitation of sharks and the destruction of their habitat has led to severe population declines and the need for conservation and management actions. Effective conservation management requires knowledge of the size at which a shark matures and an understanding of their breeding season, fundamental information to maintain appropriate population levels.MethodsHere we used reproductive endocrinology, estrogen and androgen steroids, in combination with rare direct observations of mating, visual monitoring of reproductive status such as gestation and mating scars, as well as parentage analysis, to assess reproductive biology in male and female Chondrichthyans from the wild.Results and discussionLengths at sexual maturity of female and male blacktip reef sharks corresponded closely with plasma 17β-estradiol, testosterone and 11-ketotestosterone measures respectively, but we found considerable variation in androgen levels for mature males. Size at sexual maturity of male and female blacktip reef shark deduced from direct or indirect evidence (mating scars or parentage assignment respectively, corresponded closely with plasma 17β-estradiol, testosterone and 11-ketotestosterone measures respectively, but we found considerable variation in androgen levels for mature males. Females attained sexual maturity from around 121 to 123 cm and males from 104 to 111 cm. The mating season extends from September to February but female 17β-estradiol levels are elevated 1 month prior to mating. Endocrinology has brought additional important information to the reproductive biology and ecology of blacktip reef sharks.

11-oxygenated C19 steroids as circulating androgens in women with polycystic ovary syndrome.

11-oxygenated C19 steroids (11oxC19s) are newly specified human androgens. Although median serum levels of 11oxC19 were reported to be higher in patients with polycystic ovary syndrome (PCOS) than in unaffected women, inter-individual variations in androgen levels among PCOS patients have poorly been investigated. Here, we quantified four 11oxC19s, i.e., 11-ketotestosterone (11KT), 11β-hydroxytestosterone (11OHT), 11β-hydroxyandrostenedione (11OHΔ4A), and 11-ketoandrostenedione (11KΔ4A), in blood samples of 28 PCOS patients and 31 eumenorrheic women using liquid chromatography-tandem mass spectrometry. We referred to our previous data of classic androgens in these individuals. We found that 11OHT levels were higher in the PCOS group than in the eumenorrheic group. Moreover, although the median values of 11KT, 11KΔ4A, and 11OHΔ4A were comparable between the two groups, these steroids were markedly increased in some patients. Of the 28 patients, 8 had high levels of both 11oxC19s and classic androgens, whereas 4 had an increase only in 11oxC19 levels, and 12 had an increase only in classic androgen levels. Intragroup variations in androgen levels were relatively large in the PCOS group. Levels of 11OHT and 11KT were significantly higher in overweight/obese patients than in normal weight patients and correlated with body mass indexes. These results highlight the clinical significance of 11oxC19s as circulating androgens in PCOS patients and indicate that the accumulation of 11oxC19s and/or classic androgens is an essential feature of PCOS. The profiles of circulating androgens appear to vary among patients. In particular, overweight/obesity likely enhances the 11oxC19s accumulation in PCOS, although this notion awaits further validation.

Early-moulting Red-backed Fairywren males acquire ornamented plumage in the absence of elevated androgens

ABSTRACTSexual ornaments, including plumage ornamentation, are often studied during breeding periods even though signal development can take place months earlier. This temporal disconnect potentially obscures the proximate mechanisms that underlie signal expression and development. We studied the correlation between androgen levels and expression of ornamented plumage in adult Red-backed Fairywrens (Malurus melanocephalus) 4–6 months before breeding, when signal production occurs in some, usually older, males. We found that, during this period, ornamented males, unornamented males and females all had low plasma androgen levels that did not differ from each other. Variation in androgen levels was unrelated to phenotype or moult. These findings differ from previous research conducted immediately prior to breeding in a different population of this species, which used correlative and experimental work to demonstrate that testosterone induces prenuptial moult and acquisition of ornamented plumage in younger males. Our study demonstrates that mechanisms contributing to signal production may vary within and among populations in relation to temporal, age-dependent, or geographic parameters. These results highlight the complexity of hormonal pathways to signal production, and the importance of studying signal acquisition throughout the entire period when signals are produced, as studies conducted at different time points may have quantitatively different results.

Testosterone, migration distance, and migratory timing in song sparrows Melospiza melodia

In seasonally migratory animals, migration distance often varies substantially within populations such that individuals breeding at the same site may overwinter different distances from the breeding grounds. Shorter migration may allow earlier return to the breeding grounds, which may be particularly advantageous to males competing to acquire a breeding territory. However, little is known about potential mechanisms that may mediate migration distance. We investigated naturally-occurring variation in androgen levels at the time of arrival to the breeding site and its relationship to overwintering latitude in male and female song sparrows (Melospiza melodia). We used stable isotope analysis of hydrogen (δ2H) in winter-grown claw tissue to infer relative overwintering latitude (migration distance), combined with 14years of capture records from a long-term study population to infer the arrival timing of males versus females. Relative to females, males had higher circulating androgen levels, migrated shorter distances, and were more likely to be caught early in the breeding season. Males that migrate short distances may benefit from early arrival at the breeding grounds, allowing them to establish a breeding territory. Even after controlling for sex and date, androgen levels were highest in individuals that migrated shorter distances. Our findings indicate that androgens and migration distance are correlated traits within and between sexes that may reflect individual variation within an integrated phenotype in which testosterone has correlated effects on behavioral traits such as migration.

Expression of sex steroid hormone receptors in human skeletal muscle during the menstrual cycle.

Variations in sex hormone levels during the menstrual cycle may affect neuromuscular performance and the risk of sustaining musculoskeletal injury in women. The aim of this study was to investigate mRNA and protein levels for sex steroid hormone receptors in skeletal muscle in three distinct phases of the menstrual cycle. Fifteen, healthy women with regular menstrual cycles participated in the study. Muscle biopsies from the vastus lateralis were obtained in three hormonally verified phases of the menstrual cycle for each individual, that is the follicular phase, the ovulatory phase and the luteal phase. mRNA and protein levels of oestrogen (ERα and ERβ), progesterone (PR) and androgen (AR) receptors were analysed. There was an overall significant variation in mRNA and protein levels of ERα and PR across the menstrual cycle. mRNA and protein levels of ERα were highest in the follicular phase when oestradiol levels were low, whereas protein levels of PR were highest in the luteal phase when progesterone levels were high. mRNA levels of PR were highest in the ovulatory phase. No significant variation in AR levels was detected across the menstrual cycle. ERβ levels were very low in all three phases of the menstrual cycle. Significant variations in mRNA and protein levels of ERα and PR were detected in skeletal muscle during three confirmed phases of the menstrual cycle. These results may have an impact on effects of muscular training and sports injuries in women.

Cancer and the Plow

Past research has shown that the invention of the plow played a key role in human social evolution. The physical strength required to drive a plow gave men a comparative advantage in economically productive activity; this created gender norms that have persisted to the present day. However, there is an additional channel through which the invention of the plow could have influenced modern human societies: the creation of an economic environment favoring not only the sexual division of labor but also the selection of men with more upper-body strength. In this case, modern populations descended from plow-using communities should exhibit greater sexual dimorphism than others, and greater dimorphism should be associated with higher androgen levels in males. This has a direct epidemiological implication, because the incidence of many cancers is correlated with androgen levels. Using international data on cancer incidence, we show that there is a strong association between the magnitude of sex differences in cancer risk and the proportion of the population descended from plow-using communities. Although both of these characteristics are correlated with other socio-economic factors (such as the level of economic development), controlling for such correlations does not diminish estimates of the magnitude of the association between cancer risk and plow ancestry. In addition to their implications for cancer epidemiology, the results suggest that the international variation in gender norms might also be associated with variation in androgen levels.

Social instability promotes hormone–behavior associated patterns in a cichlid fish

Androgens are known to respond to social challenges and to control the expression of social behavior and reproductive traits, such as gonadal maturation and sperm production, expression of secondary sex characters and reproductive behaviors. According to the challenge hypothesis variation in androgen levels above a breeding baseline should be explained by the regime of social challenges faced by the individual considering the trade-offs of androgens with other traits (e.g. parental care). One prediction that can be derived from the challenge hypothesis is that androgen levels should increase in response to social instability. Moreover, considering that a tighter association of relevant traits is expected in periods of environmental instability, we also predict that in unstable environments the degree of correlations among different behaviors should increase and hormones and behavior should be associated. These predictions were tested in a polygamous cichlid fish (Mozambique tilapia, Oreochromis mossambicus) with exclusive maternal care. Social instability was produced by swapping dominant males among groups. Stable treatment consisted in removing and placing back dominant males in the same group, in order to control for handling stress. Cortisol levels were also measured to monitor stress levels involved in the procedure and their relation to the androgen patterns and behavior. As predicted androgen levels increased in males in response to the establishment of a social hierarchy and presence of receptive females. However, there were no further differential increases in androgen levels over the social manipulation phase between social stable and social unstable groups. As predicted behaviors were significantly more correlated among themselves in the unstable than in the stable treatment and an associated hormone–behavior pattern was only observed in the unstable treatment.

Immune activation is inversely related to, but does not cause variation in androgen levels in a cichlid fish species

Studies on birds and mammals indicate that sexual traits may signal superior health because active immunity, like inflammatory responses to infections, is suppressive to the production of androgens that facilitate the expression of these traits. Here we test this possible pathway for honest signaling in a teleost species, Sarotherodon galilaeus, by activating the immune system with sheep red blood cells (SRBC), which is a non-pathogenic T- and B-cell stimulating antigen. Two weeks after the start of treatment adult males injected with SRBC showed a significant increase in antibody production in comparison with control males. The variation in specific antibody production was negatively related with variation in both testosterone and 11-ketotestosterone levels. This suggests that investment in immune protection is incompatible with increased activity of the hypothalamic-pituitary-gonadal axis. However, opposite to our expectation no difference in androgen levels was found between placebo and SRBC treatment suggesting that immune activation did not cause androgen suppression in our studied species.

3α-androstanediol, but not testosterone, attenuates age-related decrements in cognitive, anxiety, and depressive behavior of male rats

Some hippocampally-influenced affective and/or cognitive processes decline with aging. The role of androgens in this process is of interest. Testosterone (T) is aromatized to estrogen, and reduced to dihydrotestosterone (DHT), which is converted to 5α-androstane, 3α, 17α-diol (3α-diol). To determine the extent to which some age-related decline in hippocampally-influenced behaviors may be due to androgens, we examined the effects of variation in androgen levels due to age, gonadectomy, and androgen replacement on cognitive (inhibitory avoidance, Morris water maze) and affective (defensive freezing, forced swim) behavior among young (4 months), middle-aged (13 months), and aged (24 months) male rats. Plasma and hippocampal levels of androgens were determined. In experiment 1, comparisons were made between 4-, 13-, and 24-month-old rats that were intact or gonadectomized (GDX) and administered a T-filled or empty silastic capsule. There was age-related decline in performance of the inhibitory avoidance, water maze, defensive freezing, and forced swim tasks, and hippocampal 3α-diol levels. Chronic, long-term (1–4 weeks) T-replacement reversed the effects of GDX in 4- and 13-month-old, but not 24-month-old, rats in the inhibitory avoidance task. Experiments 2 and 3 assessed whether acute subcutaneous T or 3α-diol, respectively, could reverse age-associated decline in performance. 3α-diol, but not T, compared to vehicle, improved performance in the inhibitory avoidance, water maze, forced swim, and defensive freezing tasks, irrespective of age. Thus, age is associated with a decrease in 3α-diol production and 3α-diol administration reinstates cognitive and affective performance of aged male rats.

Seasonal Variation in Androgen Levels in the Oyster Toadfish

Male Oyster Toadfish Opsanus tau produce an advertisement call, the boatwhistle, using sexually dimorphic sonic muscles attached to the swimbladder. The fundamental frequency and duration of the boatwhistle change seasonally suggesting hormonal modulation of the output of pattern generators in the brain. The toadfish has an unusual protracted reproductive cycle in which testes contain mature sperm throughout the year, and females develop large eggs during late summer and fall for spawning the following spring although some may mate in the fall. This study quantified gonad development and plasma androgens in males and females throughout a seasonal cycle to relate them to the prolonged reproductive cycle and to quantitative changes in boatwhistle parameters. Median levels of testosterone (T) and 11- ketotestosterone (11KT) in males peak in May during the early part of the spawning season (461 pg/mL for T and 3746 for 11KT) and decline to 153 and 43 pg/mL, respectively, in June although spawning continues into July. A minor increase in gonosomatic index (GSI) and levels of both androgens (180 and 94 pg/mL, respectively) occurs in October. Median levels of T (328 pg/mL) and GSI in females also peak in May. In June, T levels drop in spawned females but remain elevated in those still gravid. Ovaries start to develop in late summer, and T levels increase above levels of individuals spawned in June. A spring peak in T in unspawned females and increasing levels in the fall correlate with estradiol (E) levels. Androgen levels do not correlate with the seasonal cycle in boatwhistle parameters suggesting that some other factor is responsible.

Functional significance of variation in egg-yolk androgens in the American coot.

Maternally derived hormones in cleidoic eggs have been implicated in mediating growth, behavior, and social interactions among offspring. Given these widespread and significant effects, hormonal investments have the potential to greatly influence fitness of offspring. Intraspecific variation can exist at three levels (within individual eggs, among eggs within clutches, and among eggs from different females), each of which has different implications for offspring. We characterized all three levels of variation in maternally derived androgens (testosterone and androstenedione) present in yolks of American coot eggs. We found no variation in testosterone levels within eggs which suggests that embryos are exposed to constant androgen levels during development, and that field-based yolk biopsies are an appropriate way to sample eggs for this species. Within clutches, early-laid eggs had higher androgen levels than late-laid eggs, and this pattern may exacerbate negative effects of hatching asynchrony on chicks from late-hatching eggs if androgens provide chicks with a behavioral or growth advantage over chicks from eggs with lower androgen levels. American coots lay large clutches, and unequal resource allocation among offspring may be the optimal strategy for females with access to limited resources. Most of the variation in androgen levels occurred among eggs from different females. Females nesting on ponds with two other pairs laid eggs with significantly higher androgen levels than females living on ponds with fewer pairs. This suggests that increased territory defense behaviors influence the levels of androgens allocated to eggs and may be one mechanism underlying density-dependent effects on reproduction.

Seasonally of adult male japanese macaques ( Macaca fuscata): Androgens and behavior in a confined troop

Seasonal variations in levels of serum testosterone, dihydrotestosterone (DHT), reproductive behavior, and social behavior were investigated in 12 adult males (5 to 20 + years of age) of the Oregon troop of Japanese macaques ( Macaca fuscata). Blood samples were collected at 2- to 4-month intervals, and behaviors were monitored twice weekly over a 15-month period. Significant seasonal variations in levels of testosterone and DHT, and in frequencies of mount series, ejaculations, number of female partners, displays, courtship, and aggression were observed. Seasonal variations in reproductive and social behaviors did not correlate with seasonal variations in androgen levels because seasonal increases in these behaviors followed seasonal increases in the androgens with a 1- to 2-month delay. However, significant correlations between increased androgen levels and the onset of mating activity occur when mean monthly frequencies of mount series are shifted 1 to 2 months earlier to coincide with the rise in serum androgen levels. The frequency of adult male play and male-male mounting increased significantly when androgen levels were low. We suggest that photoperiod changes may function as a proximate cue in male Japanese macaques which induces a state of biological readiness for mating, and the behavioral consequences (i.e., mating) are then dependent upon the presence of receptive females.

Circannual plasma androgen levels in free-living male great tits ( Parus major major L.)

Seasonal variations of plasma androgen levels in free-living adult and juvenile male Great Tits ( Parus major major L.) were measured by radioimmunoassay over a period of 5 years. In 4 of the 5 years a peak of androgen concentrations was observed during the breeding season (in 1 year during the prebreeding season, followed by a nadir during winter. Besides these circannual fluctuations, considerable variations in plasma androgen levels between comparable behavioral periods of successive years were noticed (187 to 18.5 ng/dl during the breeding season and 86 to 16 ng/dl during winter). No relationship was found between these variations and possible causative factors such as age and origin of the birds and the time of trapping and blood sampling during the day. The large between year variations in androgen levels may be caused by changes in the birds' environment including density of the population and the availability of food. Additional data are required to test this hypothesis.

Sex-limited genetic variation in a mouse salivary protein.

This report describes a gene which influences the electrophoretic mobility of a protein in the salivas of adult mice. Three categories of phenotype have been observed: the two single-banded types, F (Fast) and S (Slow), and the two-banded type, SF (Slow-Fast), with the two bands represented in varying proportions. All females, regardless of age or strain, and all males before puberty show only the F phenotype. Males of the BALB/c and C57BL/6J strains show the F phenotype throughout puberty and adult life, whereas males of the C3H/St and C57BL/KsJ strains show the SF phenotype in puberty and the S phenotype in adult life. We have designated this variation the sex-limited saliva pattern (Ssp). The results from genetic crosses indicate that the variation among the strains is determined by an autosomal locus, Ssp, with two alleles, SspS and SspF, where SspS is dominant to SspF. Testosterone treatment can accelerate the acquisition of the S type in males of the strains C3H/St and C57BL/KsJ and also induces that phenotype in C3H/St females and C57BL/6J males. Thus it appears that the observed strain-specific differences reflect a genetic variation in androgen levels and/or androgen sensitivity rather than variation in a structural gene.

Relationship between antler development and plasma androgen concentrations in adult roe deer (Capreolus capreolus)

Four male deer (4-5 years old), living in normal park conditions, were captured every 2 weeks in the year to study annual variations in androgen levels and the relationship between testicular activity and the antler cycle. Data were also obtained from 77 wild adult males (greater than 3 years old) caught in the forest. Plasma androgen concentrations rose briefly in April and markedly in August; the high values in August corresponded with the breeding period. From the time of casting to maximum growth was about 60 days; mineralization of the antlers then lasted for 45 days only. The mineralization phase of antler growth corresponded to the reactivation of testicular function in late January (0.43 +/- 0.16 to 1.99 +/- 0.42 ng androgen/ml, N = 4).