Testosterone in human studies: Modest associations between plasma and salivary measurements

The Optimal Time-lag for Testosterone Challenge Research Based on Salivary Profiles Following Different Doses of Transdermal Testosterone Administrations

In recent decades, testosterone challenge research examining the effects of testosterone on human neuropsychological behaviors has rapidly grown with the development of a single-dose transdermal testosterone administration paradigm. However, the optimal time-lag between testosterone administration and behavioral measurement is not unified, partly hindering causal understanding of the "testosterone effect". The present study aimed to investigate the optimal time-lag through LC-MS/MS-based salivary profiles of ten biomarkers among healthy males following administration of different doses of transdermal testosterone (i.e., 450- and 150-mg [Androgel®]). Results revealed that testosterone administration significantly increased salivary testosterone levels, reaching maximum levels 2 hours after 450-mg testosterone administration and 1 hour after 150-mg testosterone administration, respectively. Salivary androstenedione and DHEA increased synchronously with testosterone following administration. Moreover, the ratios of testosterone to androstenedione, DHEA, estradiol, and of androstenedione to estrone significantly elevated 1 hour after testosterone administration. In contrast, salivary cortisol and cortisone were decreased over time due to circadian rhythm rather than testosterone administration. Consistent with previous serum studies, the present salivary findings recommended 1-hour post testosterone administration as the optimal time-lag to measure the effects of testosterone on human behaviors in transdermal testosterone challenge research.

Dark Triad Personality Traits, Second-to-Forth Digit Ratio (2D:4D) and Circulating Testosterone and Cortisol Levels

INTRODUCTION

Dark Triad (DT) personality traits (psychopathy, Machiavellianism, and narcissism) show sex differences and associations with hormones. Understanding aetiology may assist in mitigating the harm of these potentially adverse characteristics. Low second-to-fourth digit ratio (2D:4D) is hypothesised to be a marker of high prenatal testosterone exposure and may provide important information about organisational hormones. The aim of the present study was to measure Dark Triad and Big 5 personality traits in relation to digit ratio, salivary testosterone, and cortisol.

METHODS

A non-clinical sample (N=268; 49.25% Female, age M25.20 ± 8.77yrs) completed the Short Dark Triad and International Personality Inventory Pool - Mini. Afternoon saliva was analysed for testosterone and cortisol, and 2D:4D finger ratios were measured.

RESULTS

Males scored higher on DT traits than females. Females scored higher on Big 5 agreeableness and neuroticism. Males had higher testosterone and cortisol levels and lower 2D:4D than females. Digit ratio correlated inversely with salivary testosterone, Machiavellianism, and psychopathy. Testosterone levels correlated positively with cortisol levels and psychopathy and negatively with agreeableness, neuroticism, and Machiavellianism.

CONCLUSIONS

These results provide indications that Machiavellianism and psychopathy (Dark Triad) traits, but not narcissism or Big 5 traits, are linked to markers of prenatal testosterone exposure. Results also replicate sex differences seen in 2D:4D digit ratios, with males having a shorter second-relative-to-forth finger. Links between circulating testosterone, digit ratios, cortisol and personality traits provide further information about potential biological bases of personality.

Screening and identification of salivary biomarkers for assessing the effects of exogenous testosterone administration on HPG and HPA axes and ECS

The contents of steroids and endocannabinoids along with the ratios between them would be candidate biomarkers for sensitively and comprehensively assessing the role of testosterone in regulating the activities of the hypothalamus-pituitary-gonadal (HPG) axis, the hypothalamus-pituitaryadrenal (HPA) axis and endogenous cannabinoid system (ECS). However, previous studies mostly used the contents rather than the ratios as biomarkers. This study aimed to systematically screen and identify sensitive biomarkers from 21 candidates including both the contents of nine steroids and one endocannabinoid and their ratios in saliva. Three screening criteria were whether there were intergroup differences, time-dependent changes and considerable relative stability during a 4-h period after exogenous testosterone administration. This study used LC-APCI⁺-MS/MS to determine the salivary levels of the candidate biomarkers on 62 male healthy undergraduates who were divided into testosterone administration and placebo control groups. The results revealed that salivary testosterone, androstenedione, DHEA and the ratios of testosterone to estradiol and AEA, and of cortisol to testosterone and DHEA were sensitive biomarkers for assessing the effects of testosterone administration on the three neuroendocrine systems because they all showed significant intergroup differences and time-dependent changes and good relative stability. Salivary cortisol, cortisone and the ratios of testosterone to androstenedione and DHEA and of androstenedione to estrone, and of cortisol to cortisone, androstenedione and AEA might be suitable biomarkers because they met only two of the three criteria, but needed to be validated in the future. The rest biomarkers were unsuitable because they mostly showed no significant intergroup differences, blunt time-dependent changes and poor relative stability.

An improved method for measurement of testosterone in human plasma and saliva by ultra-performance liquid chromatography-tandem mass spectrometry

The aim of the study was to develop and validate a practical assay of clinically relevant testosterone levels in human plasma and saliva. We performed ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis on Atlantis dC18 steel column using a mobile phase of 2-mM ammonium acetate and acetonitrile (20:80, v: v) that was delivered at 0.3 ml/min. After adding d3-testosterone as an internal standard (IS), we extracted plasma and salivary samples with methyl tert-butyl ether. Mass spectrometry was performed in electrospray positive-ion mode. Targeted ion transitions were examined at m/z 289.18 → 97.04 and 292.24 → 97.04 for testosterone and IS, respectively. We validated the method according to the US Food and Drug Administration guidelines. Elution times for testosterone and IS were both around 1.35 min. Testosterone level was linearly associated (r ² = 0.9975 and 0.9958) with peak area ratio of testosterone to IS between 0.5-50 ng/ml and 10-400 pg/ml in plasma and saliva, respectively. The coefficient of variation and bias were ≤12.6% and ≤±12.1% in plasma and ≤10.2% and ≤±5.3% in saliva. The extraction recovery of testosterone was ≥92% from plasma and ≥94% from saliva. Testosterone was stable (≥91%) for 24 h at room temperature and for 8 weeks at -20°C in both plasma and salivary samples. We report a simple, validated, UPLC-MS/MS assay that can be used to determine clinically relevant levels of testosterone in human plasma and saliva.

Revisiting the relationships of 2D:4D with androgen receptor (AR) gene and current testosterone levels: Replication study and meta-analyses

The relationships of digit ratio (2D:4D) with the length of AR (CAG)n, and testosterone levels from saliva and blood have been extensively debated over the years. This research including three studies further clarifies such controversies. To do so, we re-examined the relationships between the length of AR (CAG)n, 2D:4D, and current testosterone levels, through replication study and meta-analysis for each study. The results indicate: (a) the length of AR (CAG)n is not significantly associated with 2D:4D; (b) current testosterone levels are not significantly associated with the ratio; and (c) the length is not significantly associated with testosterone levels. Thus, AR (CAG)n and current testosterone levels are not significantly related to 2D:4D at individual level.

The Effect of Psychological Stress on Salivary Testosterone in Puberty Children

BACKGROUND

Psychological stress is a condition that is experienced by many adolescents which affect the Hypothalamic-Pituitary-Gonadal axis. Testosterone is known as a sex steroid hormone that is susceptible to acute stress and can be measured through saliva. Disruption of the reproductive system can affect the sexual maturation process.

AIM

To understand the difference in salivary testosterone levels in puberty children before and after given a stressor.

METHODS

A quasi-experimental intervention study was conducted at Antonius Bangun Mulia junior high school, Medan, North Sumatera, in July-October 2017. Subjects were students aged 12-14 years with sexual maturity G2 for boys and M2 for girls. Psychological stress intervention was generated by the Wechsler intelligence scale for children fourth edition (WISC IV). Saliva was collected before and after the intervention. The analysis was done with Wilcoxon test and a P value < 0.05 was considered significant.

RESULTS

Forty-two subjects of 24 male students and 18 female students with sexual maturation Tanner II (54.8%) and Tanner III (45.2%). This study obtained that there was a statistically significant difference in salivary testosterone levels before and after the subject was given a stressor (P = 0.015, CI 95%). This difference also was seen within sexual maturation Tanner II (P = 0.045, CI 95%). No difference was observed in testosterone levels based on gender, male students (P = 0.065, CI 95%) and female students (P = 0.112, CI 95%).

CONCLUSION

Stress can affect salivary testosterone levels. There was a statistically significant difference in salivary testosterone levels before and after psychological stress in puberty children.