Analysis of testosterone pulsatility in women with ovulatory menstrual cycles

Salivary testosterone across the menstrual cycle

Testosterone production in women is thought to systematically shift across the menstrual cycle, peaking during the mid-cycle ovulatory window, and potentially influencing women's behavior. Testosterone is a molecular intermediary to the production of estradiol, which is necessary for ovulation to occur, but the amount of testosterone escape and exposure to the peripheral tissues is not fully understood. Salivary testosterone is a common biomarker in behavioral neuroendocrinological studies and is thought to reflect the bioactive portions in serum. In N = 339 women with confirmed ovulation via luteinizing hormone tests, salivary testosterone, assayed with LC-MS/MS, was sampled four times across the mid-cycle ovulatory window the luteal phase. Within-subject analysis revealed a significant but small pattern of a mid-cycle peak and a luteal decrease at the aggregate level. However, at the individual level, there was substantial variability in the direction and magnitude of the testosterone-cycle pattern. We discuss the relevant underlying physiology, background research, issues with assay methodolody, and considerations for researchers studying testosterone levels in women.

Influence of ethanol consumption and food intake on serum concentrations of endogenous steroids

Steroid biosynthesis and biotransformation are based on a cascade of enzymatic processes being highly sensitive to various external influences. Amongst those, ethanol was shown to affect testosterone metabolism. For doping analyses, athlete steroid profiles comprise seven urinary steroid metabolites, of which relevant ratios are significantly increased following ethanol consumption. This effect is presumably based on the lack of hepatic NAD+-coenzyme as a consequence of ethanol oxidation. Only recently, testosterone (T) and androstenedione (A4) blood profiles have been introduced as additional approach for doping control. However, a potential influence of ethanol intake on testosterone biosynthesis and thus on blood steroid profiles has not been investigated so far. Therefore, steroid concentrations from 10 males and 10 females receiving an ethanol infusion up to a breath alcohol concentration of 0.5 mg/L which was hold as a plateau for two hours were conducted. Blood samples were drawn every 15 min for steroid quantification. An ethanol-dependent T/A4 increase up to 385% resulting from A4 suppression was observed in 14 volunteers. In addition, we observed sporadic A4 increases coinciding with cortisol and ACTH pulses pointing to a meal-induced adrenal stimulation. While testosterone levels in males showed diurnal variation solely, testosterone levels in some females were found to be susceptible to ethanol- and ACTH-dependent perturbations, which is thought to be due to its predominant adrenal synthesis in females. In conclusion, the results of the present study emphasize the importance of blood sampling at a sufficient time interval from food and ethanol intake. This is of interest if T and A4 are used for diagnostics in doping control.

Testosterone facilitates nonreproductive, context-appropriate pro- and anti-social behavior in female and male Mongolian gerbils

A growing body of literature suggests that testosterone (T) rapidly modulates behavior in a context-specific manner. However, the timescales in which T can rapidly mediate distinct types of behavior, such as pro- vs. anti- social responses, has not been studied. Thus, here we examined acute T influences on social behavior in male and female Mongolian gerbils in nonreproductive contexts. Females and males received an injection of either saline or T and were first tested in a social interaction test with a same-sex, familiar peer. 5 min after the peer interaction, subjects then underwent a resident-intruder test with a novel, same-sex conspecific. After another 5 min, gerbils were tested in a novel object task to test context-specificity (i.e., social vs. nonsocial) of T effects on behavior. Within 1 h, males and females injected with T exhibited more huddling with a peer but more active avoidance of and less time spent in proximity of an intruder than did animals injected with saline. T effects on behavior were specific to social contexts, such that T did not influence investigation of the novel object. Together these findings show that T rapidly promotes pro-social responses to a familiar peer and anti-social responses to an intruder in the same individuals within 5 min of experiencing these disparate social contexts. This demonstrates that T rapidly facilitates behavior in a context-appropriate manner outside the context of reproduction and reveals that rapid effects of T on behavior are not restricted to males.

Iron status in athletic females, a shift in perspective on an old paradigm

Iron deficiency is a common nutrient deficiency within athletes, with sport scientists and medical professionals recognizing that athletes require regular monitoring of their iron status during intense training periods. Revised considerations for athlete iron screening and monitoring have suggested that males get screened biannually during heavy training periods and females require screening biannually or quarterly, depending on their previous history of iron deficiency. The prevalence of iron deficiency in female athletes is higher than their male counterparts and is often cited as being a result of the presence of a menstrual cycle in the premenopausal years. This review has sought to revise our current understanding of female physiology and the interaction between primary reproductive hormones (oestrogen and progesterone) and iron homoeostasis in females. The review highlights an apparent symbiotic relationship between iron metabolism and the menstrual cycle that requires additional research as well as identifying areas of the menstrual cycle that may be primed for nutritional iron supplementation.

Ultradian rhythms in heart rate variability and distal body temperature anticipate onset of the luteinizing hormone surge

The menstrual cycle is characterized by predictable patterns of physiological change across timescales. Although patterns of reproductive hormones across the menstrual cycle, particularly ultradian rhythms, are well described, monitoring these measures repeatedly to predict the preovulatory luteinizing hormone (LH) surge is not practical. In the present study, we explored whether non-invasive measures coupled to the reproductive system: high frequency distal body temperature (DBT), sleeping heart rate (HR), sleeping heart rate variability (HRV), and sleep timing, could be used to anticipate the preovulatory LH surge in women. To test this possibility, we used signal processing to examine these measures in 45 premenopausal and 10 perimenopausal cycles alongside dates of supra-surge threshold LH and menstruation. Additionally, urinary estradiol and progesterone metabolites were measured daily surrounding the LH surge in 20 cycles. Wavelet analysis revealed a consistent pattern of DBT and HRV ultradian rhythm (2-5 h) power that uniquely enabled anticipation of the LH surge at least 2 days prior to its onset in 100% of individuals. Together, the present findings reveal fluctuations in distal body temperature and heart rate variability that consistently anticipate the LH surge, suggesting that automated ultradian rhythm monitoring may provide a novel and convenient method for non-invasive fertility assessment.

Testosterone therapy for women with low sexual desire: a position statement from the Brazilian Society of Endocrinology and Metabolism

OBJECTIVE

To summarize current evidence regarding testosterone treatment for women with low sexual desire.

MATERIALS AND METHODS

The Female Endocrinology and Andrology Department of the Brazilian Society of Endocrinology and Metabolism invited nine experts to review the physiology of testosterone secretion and the use, misuse, and side effects of exogenous testosterone therapy in women, based on the available literature and guidelines and statements from international societies.

RESULTS

Low sexual desire is a common complaint in clinical practice, especially in postmenopausal women, and may negatively interfere with quality of life. Testosterone seems to exert a positive effect on sexual desire in women with sexual dysfunction, despite a small magnitude of effect, a lack of long-term safety data, and insufficient evidence to make a broad recommendation for testosterone therapy. Furthermore, there are currently no testosterone formulations approved for women by the relevant regulatory agencies in the United States, Brazil, and most other countries, and testosterone formulations approved for men are not recommended for use by women.

CONCLUSION

Therefore, testosterone therapy might be considered if other strategies fail, but the risks and benefits must be discussed with the patient before prescription. Arch Endocrinol Metab. 2019;63(3):190-8.

Evidence for a Coupled Oscillator Model of Endocrine Ultradian Rhythms

Whereas long-period temporal structures in endocrine dynamics have been well studied, endocrine rhythms on the scale of hours are relatively unexplored. The study of these ultradian rhythms (URs) has remained nascent, in part, because a theoretical framework unifying ultradian patterns across systems has not been established. The present overview proposes a conceptual coupled oscillator network model of URs in which oscillating hormonal outputs, or nodes, are connected by edges representing the strength of node-node coupling. We propose that variable-strength coupling exists both within and across classic hormonal axes. Because coupled oscillators synchronize, such a model implies that changes across hormonal systems could be inferred by surveying accessible nodes in the network. This implication would at once simplify the study of URs and open new avenues of exploration into conditions affecting coupling. In support of this proposed framework, we review mammalian evidence for (1) URs of the gut-brain axis and the hypothalamo-pituitary-thyroid, -adrenal, and -gonadal axes, (2) UR coupling within and across these axes; and (3) the relation of these URs to body temperature. URs across these systems exhibit behavior broadly consistent with a coupled oscillator network, maintaining both consistent URs and coupling within and across axes. This model may aid the exploration of mammalian physiology at high temporal resolution and improve the understanding of endocrine system dynamics within individuals.

Dynamics of serum testosterone during the menstrual cycle evaluated by daily measurements with an ID-LC-MS/MS method and a 2nd generation automated immunoassay

BACKGROUND

Testosterone concentrations in normally cycling women are assumed to be elevated around the time of ovulation. The clinical relevance of changing testosterone concentrations during the menstrual cycle, however, is unclear. Poor performance of current direct immunoassays for testosterone at low concentrations confounds this issue. Therefore, our objective was to assess daily testosterone fluctuation during the menstrual cycle by a thoroughly validated isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) method and to evaluate whether an ARCHITECT® 2nd Generation Testosterone fully automated immunoassay is equally suited for this purpose.

METHODS

Testosterone was measured in serum obtained daily during the menstrual cycle of 25 healthy women, characterized by biochemical and physical examination.

RESULTS

Performance of the ID-LC-MS/MS method was concordant with a published reference method (y=1.007x-0.056 nmol/L; r=0.9998). Comparison of the immunoassay to ID-LC-MS/MS yielded y=1.095x+0.104 nmol/L (r=0.9031). Overall, testosterone concentrations were higher mid-cycle, but a peak was not discernible in each individual. Apart from a persistent positive bias, the immunoassay measured the same testosterone profiles as the ID-LC-MS/MS method. The reference interval in women was 0.30-1.69 nmol/L (8.7-48.7 ng/dL) for ID-LC-MS/MS and 0.50-2.00 nmol/L (14.4-57.7 ng/dL) for the immunoassay.

CONCLUSION

The elevation of mid-cycle testosterone concentrations is statistically significant, although not clinically relevant since day-to-day variation is higher and independent of the menstrual cycle. In this light, a single testosterone measurement might not be reflective of the overall testosterone status in an individual. Measurements obtained using the 2nd generation immunoassay gave comparable results across the menstrual cycle.

The association of testosterone, sleep, and sexual function in men and women

Testosterone has been the focus of several investigations and review studies in males, but few have addressed its effects on sleep and sexual function, despite evidence of its androgenic effects on circadian activity in both sexes. Studies have been conducted to understand how sleeping increases (and how waking decreases) testosterone levels and how this rhythm can be related to sexual function. This review addresses the inter-relationships among testosterone, sexual function and sleep, including sleep-disordered breathing in both sexes, specifically its effects related to sleep deprivation. In addition, hormonal changes in testosterone that occur in the gonadal and adrenal axis with obstructive sleep apnea and other conditions of chronic sleep deprivation, and which consequently affect sexual life, have also been explored. Nevertheless, hormone-associated sleep disruptions occur across a lifetime, particularly in women. The association between endogenous testosterone and sex, sleep and sleep disturbances is discussed, including the results of clinical trials as well as animal model studies. Evidence of possible pathophysiological mechanisms underlying this relationship is also described. Unraveling the associations of sex steroid hormone concentrations with sleep and sexual function may have clinical implications, as sleep loss reduces testosterone levels in males, and low sex steroid hormone concentrations have been associated with sexual dysfunction.