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"Testosterone - physiology"
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Gonadal Steroids and Body Composition, Strength, and Sexual Function in Men
This study, designed to determine the relative degree of testosterone deficiency, estradiol deficiency, or both at which undesirable bodily changes occur, showed that some features of male hypogonadism are due to both androgen deficiency and estrogen deficiency.
Testosterone therapy is prescribed for millions of men each year, and the number is increasing rapidly. Prescription sales of testosterone increased by 500% in the United States between 1993 and 2000.
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Most testosterone prescriptions are written to treat nonspecific symptoms, such as fatigue or sexual dysfunction, when accompanied by testosterone levels below the laboratory reference range. Currently, testosterone levels that are at least 2 SD below the mean value for healthy young adults are classified as low.
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Although convenient, this classification fails to consider the physiological consequences of specific testosterone levels.
More than 80% of circulating estradiol in men . . .
Journal Article
Effect of exogenous testosterone on cooperation depends on personality and time pressure
The social heuristic hypothesis posits that human cooperation is an intuitive response that is expressed especially under conditions of time-constraint. Conversely, it proposes that for individuals given an opportunity for reflection, cooperation is more likely to be curtailed by an optimizing process calibrated to maximize individual benefit in a given situation. Notably, the steroid hormone testosterone has also been implicated in intuitive decision-making, including both prosocial and anti-social behaviors, with effects strongest in men with particular dispositional characteristics. This raises the possibility that increased testosterone may augment the effects predicted by the social heuristic hypothesis, particularly among men higher in specific dispositional characteristics (dominance, impulsivity, independent self-construal: high risk for testosterone-induced antisocial behavior). Here, in a testosterone administration study with a relatively large sample of men (N = 400), we test this possibility in a double-blind, placebo-controlled paradigm, with men randomly assigned to play a one-shot public goods game either under time-pressure (forced intuition) or with a time delay (forced reflection). Results revealed that within the placebo group, time-pressure (versus forced delay) increased cooperation among low risk men, but decreased cooperation among high risk men. Testosterone further moderated this pattern by abolishing the time-pressure effect in low risk men and—in high risk men—reversing the effect by selectively reducing offers (compared to placebo) under forced delay. This is the first evidence that testosterone and personality can interact with time-pressure and delay to predict human cooperation.
Journal Article
Sex-Steroid Hormone Manipulation Reduces Brain Response to Reward
Mood disorders are twice as frequent in women than in men. Risk mechanisms for major depression include adverse responses to acute changes in sex-steroid hormone levels, eg, postpartum in women. Such adverse responses may involve an altered processing of rewards. Here, we examine how women's vulnerability for mood disorders is linked to sex-steroid dynamics by investigating the effects of a pharmacologically induced fluctuation in ovarian sex steroids on the brain response to monetary rewards. In a double-blinded placebo controlled study, healthy women were randomized to receive either placebo or the gonadotropin-releasing hormone agonist (GnRHa) goserelin, which causes a net decrease in sex-steroid levels. Fifty-eight women performed a gambling task while undergoing functional MRI at baseline, during the mid-follicular phase, and again following the intervention. The gambling task enabled us to map regional brain activity related to the magnitude of risk during choice and to monetary reward. The GnRHa intervention caused a net reduction in ovarian sex steroids (estradiol and testosterone) and increased depression symptoms. Compared with placebo, GnRHa reduced amygdala's reactivity to high monetary rewards. There was a positive association between the individual changes in testosterone and changes in bilateral insula response to monetary rewards. Our data provide evidence for the involvement of sex-steroid hormones in reward processing. A blunted amygdala response to rewarding stimuli following a rapid decline in sex-steroid hormones may reflect a reduced engagement in positive experiences. Abnormal reward processing may constitute a neurobiological mechanism by which sex-steroid fluctuations provoke mood disorders in susceptible women.
Journal Article
Testosterone decreases trust in socially naïve humans
Trust plays an important role in the formation and maintenance of human social relationships. But trusting others is associated with a cost, given the prevalence of cheaters and deceivers in human society. Recent research has shown that the peptide hormone oxytocin increases trust in humans. However, oxytocin also makes individuals susceptible to betrayal, because under influence of oxytocin, subjects perseverate in giving trust to others they know are untrustworthy. Testosterone, a steroid hormone associated with competition and dominance, is often viewed as an inhibitor of sociality, and may have antagonistic properties with oxytocin. The following experiment tests this possibility in a placebo-controlled, within-subjects design involving the administration of testosterone to 24 female subjects. We show that compared with the placebo, testosterone significantly decreases interpersonal trust, and, as further analyses established, this effect is determined by those who give trust easily. We suggest that testosterone adaptively increases social vigilance in these trusting individuals to better prepare them for competition over status and valued resources. In conclusion, our data provide unique insights into the hormonal regulation of human sociality by showing that testosterone downregulates interpersonal trust in an adaptive manner.
Journal Article
Single-dose testosterone administration increases men’s preference for status goods
In modern human cultures where social hierarchies are ubiquitous, people typically signal their hierarchical position through consumption of positional goods—goods that convey one’s social position, such as luxury products. Building on animal research and early correlational human studies linking the sex steroid hormone testosterone with hierarchical social interactions, we investigate the influence of testosterone on men’s preferences for positional goods. Using a placebo-controlled experiment (
N
= 243) to measure individuals’ desire for status brands and products, we find that administering testosterone increases men’s preference for status brands, compared to brands of similar perceived quality but lower perceived status. Furthermore, testosterone increases positive attitudes toward positional goods when they are described as status-enhancing, but not when they are described as power-enhancing or high in quality. Our results provide novel causal evidence for the biological roots of men’s preferences for status, bridging decades of animal behavioral studies with contemporary consumer research.
Testosterone is believed to be involved in social rank-related behavior. Here, the authors show that one dose of testosterone increases men’s preference for “high status” goods and brands, suggesting a role for testosterone in modern consumer behavior in men.
Journal Article
Effect of Exercise Training and Testosterone Replacement on Skeletal Muscle Wasting in Patients With Heart Failure With Testosterone Deficiency
To examine whether combined testosterone replacement and exercise training (ET) therapies would potentiate the beneficial effects of isolated therapies on neurovascular control and muscle wasting in patients with heart failure (HF) with testosterone deficiency.
From January 10, 2010, through July 25, 2013, 39 male patients with HF, New York Heart Association functional class III, total testosterone level less than 249 ng/dL (to convert to nmol/L, multiply by .03467), and free testosterone level less than 131 pmol/L were randomized to training (4-month cycloergometer training), testosterone (intramuscular injection of testosterone undecylate for 4 months), and training + testosterone groups. Muscle sympathetic nerve activity was measured using microneurography, forearm blood flow using plethysmography, body composition using dual X-ray absorptiometry, and functional capacity using cardiopulmonary test. Skeletal muscle biopsy was performed in the vastus lateralis.
Muscle sympathetic nerve activity decreased in ET groups (training, P<.01; training + testosterone, P<.01), whereas no changes were observed in the testosterone group (P=.89). Forearm blood flow was similar in all groups. Lean mass increased in ET groups (training, P<.01; training + testosterone, P<.01), whereas lean mass decreased in the testosterone group (P<.01). The response of cross-sectional area of type I (P<.01) and type II (P<.05) fibers increased in the training + testosterone group as compared with the isolated testosterone group.
Our findings provide evidence for a superior effect of combined ET and testosterone replacement therapies on muscle sympathetic nerve activity, muscle wasting, and functional capacity in patients with HF with testosterone deficiency.
Journal Article
The Effects of Circadian Rhythmicity of Salivary Cortisol and Testosterone on Maximal Isometric Force, Maximal Dynamic Force, and Power Output
Teo, W, McGuigan, MR, and Newton, MJ. The effects of circadian rhythmicity of salivary cortisol and testosterone on maximal isometric force, maximal dynamic force, and power output. J Strength Cond Res 25(6)1538-1545, 2011—The study investigated the effects of circadian rhythm of cortisol (C) and testosterone (T) on maximal force production (Fpeak) and power output (Ppeak). Twenty male university students (mean age = 23.8 ± 3.6 years, height = 177.5 ± 6.4 cm, weight = 78.9 ± 11.2 kg) performed 4 time-of-day testing sessions consisting of countermovement jumps (CMJs), squat jumps (SJ), isometric midthigh pulls (IMTPs), and a 1-repetition maximum (1RM) squat. Saliva samples were collected at 0800, 1200, 1600, and 2000 hours to assess T and C levels on each testing day. Session rate-of-perceived exertion (RPE) scores were collected after each session. The results showed that Fpeak and Ppeak presented a clear circadian rhythm in CMJ and IMTP but not in SJ. One repetition maximum squat did not display a clear circadian rhythm. Session RPE scores collected at 0800 and 2000 hours were significantly (p ≤ 0.05) higher than those obtained at 1200 and 1600 hours. Salivary T and C displayed a clear circadian rhythm with highest values at 0800 hours and lowest at 2000 hours; however, no significant correlation was found between T and C with Fpeak and Ppeak. A very strong correlation was found between Taural with Fpeak of CMJ and IMTP and Ppeak of CMJ (r = 0.86, r = 0.84 and r = 0.8, p ≤ 0.001). The study showed the existence of a circadian rhythm in Fpeak and Ppeak in CMJ and IMTP. The evidence suggests that strength and power training or testing should be scheduled later during the day. The use of Taural seemed to be a more effective indicator of physical performance than hormonal measures, and the use of session RPE should also be closely monitored because it may present a circadian rhythm.
Journal Article
Adrenarcheal hormone-related development of white matter during late childhood
•White matter fibre density and cross-section increased from ages 8.5 to 10 years.•There were no sex differences in white matter fibre development.•Changes in testosterone were associated with fibre cross-section development in the inferior fronto-occipital fasciculus.
The aim of the current study was to longitudinally examine how adrenarcheal hormones influence the development of white matter structure from age 8.5 to 10 years. Participants were 120 children (66 female; mean age 8.45 years at Time 1 and 9.97 years at Time 2) who completed two diffusion-weighted imaging scans 1.5 years apart. Morning saliva samples were taken at both assessment time points to measure levels of dehydroepiandrosterone (DHEA), its sulphate (DHEAS), and testosterone. Fixel-based analysis was performed to examine how changes in white matter fibre density (FD) and cross-section (FC) over time were associated with initial levels of hormones, and changes in hormone levels over time. Both FD and FC increased over time in a wide range of white matter tracts. Increases in testosterone over time were related to relatively weaker increases in FC in the inferior fronto-occipital fasciculus. Levels and change in DHEA and DHEAS were not related to FD or FC changes. The results demonstrated development of white matter fibre density and cross-section from age 8.5 to 10 years. Changes in adrenarcheal hormone levels showed limited, localized associations with development of white matter FC. Future research should examine the relevance of adrenarcheal hormone-related white matter development for cognitive functioning; as well as directly compare analysis techniques of white matter structure.
Journal Article
The Effects of Short-Cycle Sprints on Power, Strength, and Salivary Hormones in Elite Rugby Players
Crewther, BT, Cook, CJ, Lowe, TE, Weatherby, RP, and Gill, N. The effects of short-cycle sprints on power, strength, and salivary hormones in elite rugby players. J Strength Cond Res 25(1)32-39, 2011-This study examined the effects of short-cycle sprints on power, strength, and salivary hormones in elite rugby players. Thirty male rugby players performed an upper-body power and lower-body strength (UPLS) and/or a lower-body power and upper-body strength (LPUS) workout using a crossover design (sprint vs. control). A 40-second upper-body or lower-body cycle sprint was performed before the UPLS and LPUS workouts, respectively, with the control sessions performed without the sprints. Bench throw (BT) power and box squat (BS) 1 repetition maximum (1RM) strength were assessed in the UPLS workout, and squat jump (SJ) power and bench press (BP) 1RM strength were assessed in the LPUS workout. Saliva was collected across each workout and assayed for testosterone (Sal-T) and cortisol (Sal-C). The cycle sprints improved BS (2.6 ± 1.2%) and BP (2.8 ± 1.0%) 1RM but did not affect BT and SJ power. The lower-body cycle sprint produced a favorable environment for the BS by elevating Sal-T concentrations. The upper-body cycle sprint had no hormonal effect, but the workout differences (%) in Sal-T (r = −0.59) and Sal-C (r = 0.42) concentrations correlated to the BP, along with the Sal-T/C ratio (r = −0.49 to −0.66). In conclusion, the cycle sprints improved the BP and BS 1RM strength of elite rugby players but not power output in the current format. The improvements noted may be explained, in part, by the changes in absolute or relative hormone concentrations. These findings have practical implications for prescribing warm-up and training exercises.
Journal Article