Daily Fluctuations of Progesterone and Testosterone Are Associated With Fibromyalgia Pain Severity

The influence of sex on neuroimmune communication, pain, and physiology

With the National Institutes of Health's mandate to consider sex as a biological variable (SABV), there has been a significant increase of studies utilizing both sexes. Historically, we have known that biological sex and hormones influence immunological processes and now studies focusing on interactions between the immune, endocrine, and nervous systems are revealing sex differences that influence pain behavior and various molecular and biochemical processes. Neuroendocrine-immune interactions represent a key integrative discipline that will reveal critical processes in each field as it pertains to novel mechanisms in sex differences and necessary therapeutics. Here we appraise preclinical and clinical literature to discuss these interactions and key pathways that drive cell- and sex-specific differences in immunity, pain, and physiology.

Climacteric and fibromyalgia: a review

Fibromyalgia (FM) and climacteric conditions share common epidemiological and clinical features, with FM symptoms often beginning during menopause. Musculoskeletal pain, arthralgia, myalgia and other symptoms are frequently seen in both conditions. Some research suggests a link between the cessation of sex hormones and FM symptoms. Women with FM tend to experience more severe symptoms after menopause, and the severity of FM symptoms can worsen in women who have had a hysterectomy with or without oophorectomy. Despite these similarities, it is essential to treat FM and climacteric conditions separately and follow established guidelines for management. However, it is also important to recognize that both conditions can coexist in the same patient. It is crucial to note that there is limited evidence supporting the effectiveness of menopausal hormone therapy for primary FM management. Therefore, menopausal hormone therapy should not be recommended for FM unless the patient also has climacteric syndrome.

Identifying microRNAs Possibly Implicated in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Fibromyalgia: A Review

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and fibromyalgia (FM) are chronic syndromes of unknown etiology, accompanied by numerous symptoms affecting neurological and physical conditions. Despite frequent revisions of the diagnostic criteria, clinical practice guidelines are often outdated, leading to underdiagnosis and ineffective treatment. Our aim was to identify microRNA (miRNA) biomarkers implicated in pathological mechanisms underlying these diseases. A comprehensive literature review using publicly accessible databases was conducted. Interesting miRNAs were extracted from relevant publications on ME/CFS and/or FM, and were then linked to pathophysiological processes possibly manifesting these chronic diseases. Dysregulated miRNAs in ME/CFS and FM may serve as promising biomarkers for these diseases. Key identified miRNAs, such as miR-29c, miR-99b, miR-128, miR-374b, and miR-766, were frequently mentioned for their roles in immune response, mitochondrial dysfunction, oxidative stress, and central sensitization, while miR-23a, miR-103, miR-152, and miR-320 were implicated in multiple crucial pathological processes for FM and/or ME/CFS. In summary, both ME/CFS and FM seem to share many dysregulated biological or molecular processes, which may contribute to their commonly shared symptoms. This miRNA-based approach offers new angles for discovering molecular markers urgently needed for early diagnosis or therapeutics to tackle the pathology of these medically unexplained chronic diseases.

Local Synthesis of Estradiol in the Rostral Ventromedial Medulla Protects against Widespread Muscle Pain in Male Mice

Animal studies consistently demonstrate that testosterone is protective against pain in multiple models, including an animal model of activity-induced muscle pain. In this model, females develop widespread muscle hyperalgesia, and reducing testosterone levels in males results in widespread muscle hyperalgesia. Widespread pain is believed to be mediated by changes in the central nervous system, including the rostral ventromedial medulla (RVM). The enzyme that converts testosterone to estradiol, aromatase, is highly expressed in the RVM. Therefore, we hypothesized that testosterone is converted by aromatase to estradiol locally in the RVM to prevent development of widespread muscle hyperalgesia in male mice. This was tested through pharmacological inhibition of estrogen receptors (ERs), aromatase, or ER-α in the RVM which resulted in contralateral hyperalgesia in male mice (C57BL/6J). ER inhibition in the RVM had no effect on hyperalgesia in female mice. As prior studies show modulation of estradiol signaling alters GABA receptor and transporter expression, we examined if removal of testosterone in males would decrease mRNA expression of GABA receptor subunits and vesicular GABA transporter (VGAT). However, there were no differences in mRNA expression of GABA receptor subunits of VGAT between gonadectomized and sham control males. Lastly, we used RNAscope to determine expression of ER-α in the RVM and show expression in inhibitory (VGAT+), serotonergic (tryptophan hydroxylase 2+), and μ-opioid receptor expressing (MOR+) cells. In conclusion, testosterone protects males from development of widespread hyperalgesia through aromatization to estradiol and activation of ER-α which is widely expressed in multiple cell types in the RVM.

Supportive care of female hormones in brain health: what and how?

Female hormones, functioning as neuroactive steroids, are utilized beyond menopausal hormone therapy. The rapid onset of allopregnanolone analogs, such as brexanolone and zuranolone, in treating depression, and the effectiveness of megestrol acetate in addressing appetite and weight gain, prompted the Food and Drug Administration to authorize the use of progesterone for treating postpartum depression and cancer-related cachexia. Progesterone has also been found to alleviate neuropathic pain in animal studies. These off-label applications offer a promising option for patients with advanced cancer who often experience various mood disorders such as depression, persistent pain, social isolation, and physical complications like cachexia. These patients have shown low tolerance to opioids and mood-regulating medications. However, the potential risks and uncertainties associated with hormone therapy treatment modalities can be daunting for both patients and medical professionals. This review aims to offer a comprehensive understanding of the non-reproductive functions and mechanisms of female hormones in brain health.

Fibromyalgia pathogenesis explained by a neuroendocrine multistable model

Fibromyalgia (FM) is a central disorder characterized by chronic pain, fatigue, insomnia, depression, and other minor symptoms. Knowledge about pathogenesis is lacking, diagnosis difficult, clinical approach puzzling, and patient management disappointing. We conducted a theoretical study based on literature data and computational analysis, aimed at developing a comprehensive model of FM pathogenesis and addressing suitable therapeutic targets. We started from the evidence that FM must involve a dysregulation of central pain processing, is female prevalent, suggesting a role for the hypothalamus-pituitary-gonadal (HPG) axis, and is stress-related, suggesting a role for the HP-adrenocortical (HPA) axis. Central pathogenesis was supposed to involve a pain processing loop system including the thalamic ventroposterolateral nucleus (VPL), the primary somatosensory cortex (SSC), and the thalamic reticular nucleus (TRN). For decreasing GABAergic and/or increasing glutamatergic transmission, the loop system crosses a bifurcation point, switching from monostable to bistable, and converging on a high-firing-rate steady state supposed to be the pathogenic condition. Thereafter, we showed that GABAergic transmission is positively correlated with gonadal-hormone-derived neurosteroids, notably allopregnanolone, whereas glutamatergic transmission is positively correlated with stress-induced glucocorticoids, notably cortisol. Finally, we built a dynamic model describing a multistable, double-inhibitory loop between HPG and HPA axes. This system has a high-HPA/low-HPG steady state, allegedly reached in females under combined premenstrual/postpartum brain allopregnanolone withdrawal and stress condition, driving the thalamocortical loop to the high-firing-rate steady state, and explaining the connection between endocrine and neural mechanisms in FM pathogenesis. Our model accounts for FM female prevalence and stress correlation, suggesting the use of neurosteroid drugs as a possible solution to currently unsolved problems in the clinical treatment of the disease.

Adrenalectomy attenuates hyperalgesia but does not regulate muscle wasting in a female rat model of fibromyalgia

Although it is well established that fibromyalgia (FM) syndrome is characterized by chronic diffuse musculoskeletal hyperalgesia, very little is known about the effect of this pathology on muscle tissue plasticity. Therefore, the present study aimed to characterize the putative alterations in skeletal muscle mass in female rats subjected to a FM model by inducing chronic diffuse hyperalgesia (CDH) through double injections of acidic saline (pH 4.0) into the left gastrocnemius muscle at 5-day intervals. To determine protein turnover, the total proteolysis, proteolytic system activities and protein synthesis were evaluated in oxidative soleus muscles of pH 7.2 (control) and pH 4.0 groups at 7 days after CDH induction. All animals underwent behavioural analyses of mechanical hyperalgesia, strength and motor performance. Our results demonstrated that, in addition to hyperalgesia, rats injected with acidic saline exhibited skeletal muscle loss, as evidenced by a decrease in the soleus fibre cross-sectional area. This muscle loss was associated with increased proteasomal proteolysis and expression of the atrophy-related gene (muscle RING-finger protein-1), as well as reduced protein synthesis and decreased protein kinase B/S6 pathway activity. Although the plasma corticosterone concentration did not differ between the control and pH 4.0 groups, the removal of the adrenal glands attenuated hyperalgesia, but it did not prevent the increase in muscle protein loss in acidic saline-injected animals. The data suggests that the stress-related hypothalamic-pituitary-adrenal axis is involved in the development of hyperalgesia, but is not responsible for muscle atrophy observed in the FM model induced by intramuscular administration of acidic saline. Although the mechanisms involved in the attenuation of hyperalgesia in rats injected with acidic saline and subjected to adrenalectomy still need to be elucidated, the results found in this study suggest that glucocorticoids may not represent an effective therapeutic approach to alleviate FM symptoms.

How Sex Hormones Affect Migraine: An Interdisciplinary Preclinical Research Panel Review

Sex hormones and migraine are closely interlinked. Women report higher levels of migraine symptoms during periods of sex hormone fluctuation, particularly during puberty, pregnancy, and perimenopause. Ovarian steroids, such as estrogen and progesterone, exert complex effects on the peripheral and central nervous systems, including pain, a variety of special sensory and autonomic functions, and affective processing. A panel of basic scientists, when challenged to explain what was known about how sex hormones affect the nervous system, focused on two hormones: estrogen and oxytocin. Notably, other hormones, such as progesterone, testosterone, and vasopressin, are less well studied but are also highlighted in this review. When discussing what new therapeutic agent might be an alternative to hormone therapy and menopause replacement therapy for migraine treatment, the panel pointed to oxytocin delivered as a nasal spray. Overall, the conclusion was that progress in the preclinical study of hormones on the nervous system has been challenging and slow, that there remain substantial gaps in our understanding of the complex roles sex hormones play in migraine, and that opportunities remain for improved or novel therapeutic agents. Manipulation of sex hormones, perhaps through biochemical modifications where its positive effects are selected for and side effects are minimized, remains a theoretical goal, one that might have an impact on migraine disease and other symptoms of menopause. This review is a call to action for increased interest and funding for preclinical research on sex hormones, their metabolites, and their receptors. Interdisciplinary research, perhaps facilitated by a collaborative communication network or panel, is a possible strategy to achieve this goal.

Unraveling the Complex Web of Fibromyalgia: A Narrative Review

Fibromyalgia is a complex and often misunderstood chronic pain disorder. It is characterized by widespread musculoskeletal pain, fatigue, and heightened sensitivity, and has evolved in diagnostic criteria and understanding over the years. Initially met with skepticism, fibromyalgia is now recognized as a global health concern affecting millions of people, with a prevalence transcending demographic boundaries. The clinical features and diagnosis of fibromyalgia encompass a range of symptoms beyond pain, including sleep disturbances and cognitive difficulties. This study emphasizes the importance of a comprehensive evaluation for accurate diagnosis, considering the shift from tender point reliance to a more holistic approach. Etiology and pathophysiology involve genetic predisposition, neurotransmitter dysregulation, central sensitization, and immune system involvement. Risk factors such as gender, age, family history, and comorbid conditions contribute to susceptibility. The impact on quality of life is profound, affecting physical and social aspects, often accompanied by mood disorders. Management approaches include pharmacological interventions, non-pharmacological therapies, lifestyle modifications, and alternative treatments. This study also delves into emerging research, exploring advances in neurobiological understanding, brain imaging, genetic markers, glutamate modulation, cannabinoids, gut microbiome, and digital health tools for fibromyalgia management. Overall, this study provides a nuanced and up-to-date overview of the complexities surrounding fibromyalgia, aiming to enhance understanding and support for individuals grappling with this challenging condition.

The Effects of Sex Hormones on Postoperative Pain in Patients with Laparoscopic Cholecystectomy

OBJECTIVE

There are many factors that affect postoperative pain. This study determines the effect of preoperative sex hormone levels on postoperative pain levels in patients undergoing laparoscopic cholecystectomy.

PATIENTS AND METHODS

This study included a total of 89 patients who met the study inclusion criteria. The patients were divided into 3 groups based on their sex and pre and postmenopausal periods: male patients (n = 28), postmenopausal female patients (n = 31), and female patients with normal cycles (n = 30). Normal-cycle women were also regrouped based on their follicular and luteal phases. Data were collected using a descriptive characteristics form, a patient follow-up form, and the Visual Analog Scale.

RESULTS

Venous blood samples taken from the patients before surgery were used to measure their levels of estradiol (EST), testosterone (TES), and progesterone levels. Male patients had lower pain levels than female patients. The male patients' Visual Analog Scale scores were inversely related and correlated strongly with their TES levels ( P < 0.05). However, subgroup analyses suggested that their EST level played a primary role in males and that the EST/TES ratio was determinant in the late postoperative period. In female patients, the EST/progesterone ratio was the most determining factor for the level of pain felt in the postmenopausal period, whereas there was no change in the premenopausal period at different stages of the menstrual cycle.

CONCLUSIONS

Sex hormones were found to be effective in predicting postoperative pain severity.

Altered response to Toll-like receptor 4 activation in fibromyalgia: A low-dose, human experimental endotoxemia pilot study

In this pilot study, a human intravenous injection of low-dose endotoxin (lipopolysaccharide, LPS) model was used to test if fibromyalgia is associated with altered immune responses to Toll-like receptor 4 (TLR4) activation. Eight women with moderately-severe fibromyalgia and eight healthy women were administered LPS at 0.1 ng/kg in session one and 0.4 ng/kg in session two. Blood draws were collected hourly to characterize the immune response. The primary analytes of interest, leptin and fractalkine, were assayed via commercial radioimmunoassay and enzyme-linked immunosorbent assay kits, respectively. Exploratory analyses were performed on 20 secreted cytokine assays by multiplex cytokine panels, collected hourly. Exploratory analyses were also performed on testosterone, estrogen, and cortisol levels, collected hourly. Additionally, standard clinical complete blood counts with differential (CBC-D) were collected before LPS administration and at the end of the session. The fibromyalgia group demonstrated enhanced leptin and suppressed fractalkine responses to LPS administration. In the exploratory analyses, the fibromyalgia group showed a lower release of IFN-γ, CXCL10, IL-17A, and IL-12 and higher release of IL-15, TARC, MDC, and eotaxin than the healthy group. The results of this study suggest that fibromyalgia may involve an altered immune response to TLR4 activation.

Pubertal development and pain incidence and characteristics in children: a 1-year prospective cohort study of a national sample

ABSTRACT

Sex differences in pain become apparent during puberty. However, the influence of key pubertal characteristics and pubertal hormones on pain is largely unknown. We examined the prospective associations between self-reported and hormone-indicated pubertal characteristics and pain incidence and severity in 10- to 11-year-old pain-free youth in the Adolescent Brain Cognitive Development (ABCD) Study over 1 year. Puberty was measured at baseline and follow-up with self-report (Pubertal Development Scale [PDS]) and hormonal assessment (salivary dehydroepiandrosterone [DHEA], testosterone, and estradiol). Pain status (yes/no), intensity, and interference (0-10 numerical rating scale) in the past month were self-reported at follow-up. Pubertal maturity, progression, and asynchrony were examined in relation to pain onset and severity through confounder-adjusted generalized estimating equations modified Poisson and linear mixed regression models. Among 6631 pain-free youth at baseline, 1-year incident pain was 30.7%. In both sexes, higher PDS scores were associated with greater risk of pain onset (relative risk [RR] = 1.10 to 1.27, P s < 0.01). In boys, higher PDS item variance was associated with greater pain incidence (RR = 1.11, 95% CI, 1.03-1.20) and interference (beta = 0.40, 95% CI, 0.03-0.76); higher PDS overall and gonadal scores were associated with higher pain intensity ( P s < 0.05). Associations with hormones were seen in boys only, with each 10-fold higher testosterone levels associated with a 40% lower risk of pain incidence (95% CI, -55% to -22%) and 1.30-point lower (95% CI, -2.12 to -0.48) pain intensity, and higher DHEA levels were associated with lower pain intensity ( P = 0.020). Relationships between pubertal development and pain in peripubertal adolescents are sex specific and puberty measurement specific and warrant further investigation.

Assessment of the therapeutic potential of lutein and beta-carotene nanodispersions in a rat model of fibromyalgia

Fibromyalgia (FM) is a chronic disorder characterized by widespread musculoskeletal pain, fatigue, and cognitive impairment. Despite the availability of various treatment options, FM remains a challenging condition to manage. In the present study, we investigated the efficacy of formulated nanodispersions of lutein and beta-carotene in treating FM-related symptoms induced by reserpine in female Wistar rats. Several techniques have been implemented to assess this efficacy at various levels, including biochemical, bioelectrical, and behavioral. Namely, oxidative stress markers, monoamine levels, electrocorticography, pain threshold test, and open field test were conducted on control, FM-induced, and FM-treated groups of animals. Our results provided compelling evidence for the efficacy of carotenoid nanodispersions in treating FM-related symptoms. Specifically, we found that the dual action of the nanodispersion, as both antioxidant and antidepressant, accounted for their beneficial effects in treating FM. With further investigation, nano-carotenoids and particularly nano-lutein could potentially become an effective alternative treatment for patients with FM who do not respond to current treatment options.

Interleukin-10-producing monocytes contribute to sex differences in pain resolution in mice and humans

Pain is closely associated with the immune system, which exhibits sexual dimorphism. For these reasons, neuro-immune interactions are suggested to drive sex differences in pain pathophysiology. However, our understanding of peripheral neuro-immune interactions on sex differences in pain resolution remains limited. Here, we have shown, in both a mouse model of inflammatory pain and in humans following traumatic pain, that males had higher levels of interleukin (IL)-10 than females, which were correlated with faster pain resolution. Following injury, we identified monocytes (CD11b+ Ly6C+ Ly6G-F4/80 mid ) as the primary source of IL-10, with IL-10-producing monocytes being more abundant in males than females. In a mouse model, neutralizing IL-10 signaling through antibodies, genetically ablating IL-10R1 in sensory neurons, or depleting monocytes with clodronate all impaired the resolution of pain hypersensitivity in both sexes. Furthermore, manipulating androgen levels in mice reversed the sexual dimorphism of pain resolution and the levels of IL-10-producing monocytes. These results highlight a novel role for androgen-driven peripheral IL-10-producing monocytes in the sexual dimorphism of pain resolution. These findings add to the growing concept that immune cells play a critical role in resolving pain and preventing the transition into chronic pain.

Graphical abstract

"Do you want a period?" Launching and evaluating a brief contraceptive decision-making educational intervention

OBJECTIVE

Do you want a period? empowers people who menstruate to better understand their reproductive health and contraceptive choices through informed patient-centered contraceptive decision-making.

METHODS

Researchers partnered with the WISE (Women in the South-East) Telehealth Network to design, implement and evaluate the Do you want a period? brief educational intervention. Participants completed a longitudinal research study, including a web-based survey at baseline and a mobile-optimized text-based survey up to 6 weeks following baseline.

RESULTS

Do you want a period? was believable (93%, n = 79), informative (89%, n = 76), and helpful (85%, n = 72). Participants who reported that the intervention was helpful were significantly more likely to be satisfied with the usefulness of information provided (OR 5.61 [95% CI 1.65-19.12]), the overall quality of services (OR 3.39 [95% CI 1.04-11.08)], and obtaining necessary medical care (OR 2.40 [95% CI 1.08-5.33)]. At longitudinal follow-up, participants who received contraceptive services reported high acceptability of intervention (4.51 (±0.53) out of 5).

CONCLUSIONS

Do you want a period? envisions a new dialogue between women and clinicians, family, and friends. This brief educational intervention supports people who menstruate to determine if a safe and effective tailored contraceptive regimen is right for them.

A Cross-Sectional Study of Fibromyalgia and Post-acute COVID-19 Syndrome (PACS): Could There Be a Relationship?

Background Post-acute COVID-19 syndrome (PACS) is a syndrome characterized by a wide spectrum of symptoms emerging after clearance of coronavirus 2019 (COVID-19) infection. These symptoms include fatigue, myalgia, arthralgia, cognitive dysfunction, and many other psychiatric symptoms. Given that fibromyalgia patients have similar symptoms, we conducted a web-based cross-sectional study to investigate the prevalence and predictors of fibromyalgia patients who recovered from COVID-19. Methods Data were collected between the 9th and 19th of March 2022 using a web-based survey. The questionnaire consisted of 25 questions gathering sociodemographic information, comorbid diseases and features of acute COVID-19 infection. Lastly, the American College of Rheumatology (ACR) survey criteria completed the questionnaire. Results A final sample of 404 individuals (75% women) filled out the form. Of these, 80 (19.8%) satisfied the ACR survey criteria for fibromyalgia (93.8% women). A multivariate logistic regression model including demographic and clinical factors showed that female gender (OR: 6.557, 95% CI: 2.376 - 18.093, p = 0.001) and dyspnea (OR: 1.980, 95% CI: 1.146 - 3.420, p = 0.014) were the strongest predictors of being classified as having post-COVID-19 fibromyalgia. Bivariate correlation revealed that age (r = 0.200, p = 0.001) and duration of COVID-19 infection (r = 0.121, p = 0.015) were directly correlated with fibromyalgia symptom (FS) score. Conclusion Our data suggest that clinical features of fibromyalgia are common in patients who recovered from COVID-19 and that dyspnea and female gender increase the risk of developing post-COVID-19 fibromyalgia.

Protective assessment of progesterone and its receptor on experimental diabetic neuropathy: Antioxidant and anti-inflammatory effects

Diabetes induces a disorder in mitochondrial activity, which causes damage to the nuclear and mitochondrial DNA and ultimately increases the release of inflammatory cytokines and damages the sciatic nerve and dorsal root ganglion and induces neuropathy. It has been shown that progesterone has anti-inflammatory and antioxidative effects and prevents nerve cell damage. Therefore, the aim of this experiment was to investigate the effect of progesterone receptor neuroprotection on diabetic neuropathy. Forty male Sprague-Dawley rats were divided into four groups, including control group, diabetic control group, diabetic control group + progesterone (30 mg/kg), and diabetic control group + combination of progesterone (30 mg/kg) and RU486 (10 mg/kg). After the induction of diabetes, blood glucose level, body weight, behavioral tests, electrophysiological tests, oxidative and inflammatory factors, and histological parameters were measured. Progesterone treatment significantly reduced the level of sensitivity to hot plate without significant effect on glucose level, and significant changes were also observed in the results of tail flick test. In addition, the results showed that the administration of progesterone can improve MNCV and significantly reduce the serum levels of oxidative stress and inflammatory factors, as well as inflammation and edema around the sciatic nerve. However, RU486 inverted the beneficial effects of progesterone. Progesterone can be considered as a protective agent in reducing DN because of its ability to reduce inflammation and nerve damage. In addition, RU486, a progesterone receptor blocker, inhibits the beneficial effects of progesterone on the DN; thus, progesterone receptors play an important role in the neuroprotective effect of progesterone.

Testosterone administration enhances the expectation and perception of painful and non-painful somatosensory stimuli

The influence of testosterone on pain perception remains inconsistent in the literature. This randomized, placebo-controlled, double-blind, crossover study investigated the effect of testosterone administration on perception and expectation of electrocutaneous stimulus. Thirty healthy male participants received a single dose of testosterone in one session and a placebo in the other session. For each session, they completed a pain-rating task in which a predictability cue was inserted before a painful or non-painful electocutaneous stimulus delivery, while neural activity was simultaneously recorded by a 64-channel electroencephalographic (EEG) system. Expected and perceived pain ratings, as well as event-related potentials (ERPs) to electocutaneous stimuli and prestimulus EEG oscillatory activities while expecting upcoming electocutaneous stimuli were comprehensively compared between testosterone and placebo sessions. Compared with the placebo session, participants in the testosterone session reported greater pain rating and exhibited greater amplitude of N1 component on ERPs when perceiving both painful and non-painful electrocutaneous stimuli. Mediation analysis revealed that testosterone enhanced the pain-intensity ratings via the N1 response to the electrocutaneous stimulus. Upon viewing the predictability cues after testosterone administration, expected pain intensity increased and spontaneous low-frequency α-oscillation power in the frontal region decreased. These results provide evidence that testosterone enhanced perception and expectation of somatosensory events, and that this was a general effect rather than pain-specific. A plausible explanation for these findings is that testosterone acts to increase vigilance and sustained attention levels, as evidenced by the decreased α-oscillation power. Thus, our findings support a causal role for testosterone in heightening the biological salience of incoming somatosensory information.

Spinal dopaminergic D1-and D2-like receptors have a sex-dependent effect in an experimental model of fibromyalgia

There is evidence about the importance of sex in pain. The purpose of this study was to investigate the effect of sex in the antiallodynic activity of spinal dopamine D₁-and D₂-like receptors in a model of fibromyalgia-type pain in rats. Reserpine induced the same extent of tactile allodynia in female and male rats. Intrathecal injection of SCH- 23390 (3-30 nmol, D₁-like receptor antagonist), pramipexole (0.15-15 nmol) or quinpirole (1-10 nmol D₂-like receptor agonists) increased withdrawal threshold in reserpine-treated female rats. Those drugs induced a greater antiallodynic effect in female rats. Sex-difference was also observed in a nerve injury model. Ovariectomy abated the antiallodynic effect of SCH- 23390 (30 nmol) in reserpine-treated rats, while systemic reconstitution of 17β-estradiol levels or intrathecal injection estrogen receptor-α agonist protopanaxatriol in ovariectomized reserpine-treated females restored the antiallodynic effect of SCH- 23390. Intrathecal administration of ICI-182,780 (estrogen receptor-α/β antagonist) or methyl-piperidino-pyrazole hydrate (estrogen receptor-α antagonist) abated 17β-estradiol-restored antiallodynic effect of SCH- 23390 in rats. In contrast, ovariectomy slightly reduced the effect of pramipexole (15 nmol) or quinpirole (10 nmol) in reserpine-treated rats, whereas systemic reconstitution of 17β-estradiol levels did not modify the antiallodynic effect of both drugs. Combination 17β-estradiol/progesterone, but not 17β-estradiol nor progesterone alone, restored the antiallodynic effect of pramipexole and quinpirole in the rats. Mifepristone (progesterone receptor antagonist) abated 17β-estradiol + progesterone restoration of antiallodynic effect of pramipexole and quinpirole. These data suggest that the antiallodynic effect of dopamine D₁-and D₂-like receptors in fibromyalgia-type pain depends on spinal 17β-estradiol/estrogen receptor-α and progesterone receptors, respectively.

Fibromyalgia in Pregnancy: Neuro-Endocrine Fluctuations Provide Insight into Pathophysiology and Neuromodulation Treatment

Fibromyalgia (FM) is a chronic pain disorder with unclear pathophysiological mechanisms, which leads to challenges in patient management. In addition to pain, the disorder presents with a broad range of symptoms, such as sleep disruption, chronic fatigue, brain fog, depression, muscle stiffness, and migraine. FM has a considerable female prevalence, and it has been shown that symptoms are influenced by the menstrual cycle and periods of significant hormonal and immunological changes. There is increasing evidence that females with FM experience an aggravation of symptoms in pregnancy, particularly during the third trimester and after childbirth. In this perspective paper, we focus on the neuro-endocrine interactions that occur between progesterone, allopregnanolone, and cortisol during pregnancy, and propose that they align with our previously proposed model of FM pathogenesis based on GABAergic "weakening" in a thalamocortical neural loop system. Based on our hypothesis, we introduce the possibility of utilizing transcranial direct current stimulation (tDCS) as a non-invasive treatment potentially capable of exerting sex-specific effects on FM patients.

The Role of Sex Hormones in Pain-Related Conditions

Millions of people are affected by pain-related conditions worldwide. Literature has consistently shown that each individual experiences and perceives pain in a unique manner due to biological, environmental, and cultural factors in which they have been raised. It has been established that biological males and females perceive pain differently and that it may be partially explained by their distinct hormonal profiles since birth, which are only further magnified during puberty. For biological males, high levels of testosterone have shown to increase their pain threshold; and for biological females, estrogen fluctuations have shown to increase pain intensity and perception. However, sex hormones have not been studied in the context of pain treatment or their impact on biochemical pathways involved in pain perception. For this purpose, the transgender community serves as a unique population to investigate the impact of hormone replacement therapy on molecular pathways involved in the perception of pain. The purpose of this review is to explore the biochemistry of hormone replacement in transgender patients who also have other pain-related conditions such as headaches, fibromyalgia, temporomandibular myalgia, and visceral pain.

Nurses' role in the management of persons with chronic urogenital pelvic pain syndromes: A scoping review

BACKGROUND

Pelvic pain has cognitive, behavioral, sexual, and emotional consequences. Nurses involved in pelvic floor rehabilitation clinics have contacts with patients reporting chronic pain and should know the most appropriate service for patient referral, to submit the problem to professionals capable of correctly assessing and managing the condition. Furthermore, in some countries nurses can use conservative methods to treat the painful symptoms inside a multidisciplinary team such as breathing retraining, biofeedback, and noninvasive neuromodulation. This paper aims to provide an overview of the literature regarding the role of rehabilitation nurses in dealing with patients suffering from chronic urogenital pelvic pain or urogenital painful syndromes, inside a multidisciplinary team.

METHODS

Scoping review on Pubmed, CINAHL, Embase, Scopus, Web of Science including trials, reviews, case studies or series, and other descriptive studies regarding the role of nurses inside the multidisciplinary team in the management of males and females presenting chronic pelvic pain (CPP) or chronic pelvic pain syndrome (CPPS).

RESULTS

The 36 papers included in this review allowed answering research questions in four areas of nursing: collecting basic information, referring the person to appropriate services, evidence-based nursing interventions for CPP and CPPS, and proper documentation. Clinical history and assessment of breathing pattern, Muscular assessment and research of trigger points are the main points of data collection. Techniques for muscular relaxation and breathing retraining are important aspects of treatment, as well as biofeedback and noninvasive neuromodulation where the law allows nurses to practice such techniques. The McGill pain questionnaire and the pain inventory of the International Pain Society allow systematic data collection and handover.

CONCLUSION

Rehabilitation nurses work inside multidisciplinary teams when dealing with persons suffering from pelvic pain; further research is needed as our comprehension of the underlying pathophysiological mechanisms of CPP and CPPS evolve.

Characterizing fibromyalgia flares: a prospective observational study

Introduction

Although most patients with fibromyalgia describe periods of exacerbation of their symptomatology, there are very few studies describing its characteristics.

Material and methods

We recruited a total of 124 patients from our outpatient clinics who agreed to a follow-up of at least 6 months. All of them were asked to note and describe whether they had had any worsening of their symptoms during that time.

Results

Sixty-nine patients (75%) reported at least one flare, with a mean of 2 flares per patient. The mean duration of flares was 11 weeks. The most frequent triggers were: continuous stress (56%), intense stress (39%), physical overexertion (37%) and climatic changes (36%). The most common actions taken by patients were rest and medication.

Conclusions

Two-thirds of fibromyalgia patients experienced flares within 6 months. The symptoms and measures taken are similar to those patients usually take when they notice a worsening of symptoms.

Subcategories of Fibromyalgia: A New Concept

Fibromyalgia has previously been categorized as primary, secondary, and juvenile fibromyalgia. However, these definitions do not adequately explain the etiopathology of disease, nor do they help direct new specific therapies. Herein, we review the previously known categorizations of fibromyalgia. Based on common patient characteristics and previously studied pathophysiologies, we propose new subcategorizations of fibromyalgia that we have self-narrated, including hormonal fibromyalgia, neuroendocrine fibromyalgia, psychologic fibromyalgia, inflammatory fibromyalgia, and lastly, neuropathic fibromyalgia. Future research needs to be done to verify, add to, and fully describe these self-narrated categories of fibromyalgia that we have proposed.

Biological sex, by-products, and other continuous variables

Sex/gender is a continuous variable that researchers frequently treat as dichotomous. This practice can mask continuous underlying adaptive traits and yield spurious dichotomous "sex differences." As such, many sex differences in self-protection may be evolutionary by-products of underlying adaptations rather than adaptations themselves. Binary analysis of continuous sex/gender is ill-considered science that can contribute to inequality and counterproductive public policy.

Effect of Exercises on Central and Endocrine System for Pain Modulation in Primary Dysmenorrhea

Dysmenorrhea is the term for describing complex menstrual flow and painful spasmodic cramps during menstruation, and pain without any pathology is considered Primary Dysmenorrhea (PD). It is the most frequent ailment among women of all ages and races. The pain is dull and throbbing in character and occurs in the lower back and abdomen. Symptoms commonly appear 6 to 12 months after menarche, with the most significant incidence in the late teen and early twenties. Physical exercise is nearly a new non-medical intervention to relieve PD associated pain. Aerobics, stretching and Resistive exercises for 8-12 weeks, either supervised or unsupervised, relieves pain. Exercises are believed to cause hormonal changes in the uterine lining, which reduces PD symptoms. Researchers have presumed different pain-relieving methods, ranging from non-opioids to opioids to hormonal for variations in pain sensitivity. Exercise-induced analgesia provides the central pathway as the primary mechanism for pain reduction while, another way to reducing pain in PD may be a hormonal interaction. The hormonal changes causing exercise-induced pain modulation during the menstruation cycle is not clearly understood and the interaction and activation of all the central and endocrine components, which is a complex mechanism, is also not explained clearly. This study briefly reviews the physiological mechanism of Exercise-induced analgesia and its potent roles in controlling the pathogenesis of PD for pain relief.

Androgens, Endometriosis and Pain

The intriguing relationship between androgens, endometriosis and chronic pain continues to unfold. Determining this relationship is of crucial importance to gynecologists managing people with these conditions, as common treatments dramatically alter her hormonal profiles, with both intended and unintended consequences. Although they may be present in the same individual, there is a recognized disconnect between pain or pain-related symptoms, and the presence or extent of endometriosis lesions. Reduced androgen levels provide a potential mechanism to link the development of endometriosis lesions and the presence of chronic pain. This research paper expands the presentation of our research at the World Endometriosis Congress in 2021, subsequently published in the Journal of Pain Research which demonstrated a strong inverse relationship between androgen levels and days per month of pelvic and period pain. Here we extend and further explore the evidence for a role for androgens in the etiology and management of dysmenorrhea and pelvic pain in women, both with and without endometriosis. We explore the potential for inflammation to induce low androgen levels and consider ways in which clinicians can optimize levels of androgens when treating women with these conditions. This article prompts the question: Is it estrogens that predispose people to a life of pain, or androgens that are protective?

Sensory Neurons, Neuroimmunity, and Pain Modulation by Sex Hormones

The inclusion of women in preclinical pain studies has become more commonplace in the last decade as the National Institutes of Health (NIH) released its "Sex as a Biological Variable" mandate. Presumably, basic researchers have not had a comprehensive understanding about neuroimmune interactions in half of the population and how hormones play a role in this. To date, we have learned that sex hormones contribute to sexual differentiation of the nervous system and sex differences in behavior throughout the lifespan; however, the cycling of sex hormones does not always explain these differences. Here, we highlight recent advances in our understanding of sex differences and how hormones and immune interactions influence sensory neuron activity to contribute to physiology and pain. Neuroimmune mechanisms may be mediated by different cell types in each sex, as the actions of immune cells are sexually dimorphic. Unfortunately, the majority of studies assessing neuronal contributions to immune function have been limited to males, so it is unclear if the mechanisms are similar in females. Finally, pathways that control cellular metabolism, like nuclear receptors, have been shown to play a regulatory role both in pain and inflammation. Overall, communication between the neuroimmune and endocrine systems modulate pain signaling in a sex-dependent manner, but more research is needed to reveal nuances of these mechanisms.

Animal models of fibromyalgia: What is the best choice?

Fibromyalgia (FM) is a complex syndrome, with an indefinite aetiology and intricate pathophysiology that affects 2 - 3% of the world population. From the beginning of the 2000s, experimental animal models have been developed to mimic clinical FM and help obtain a better understanding of the relevant neurobiology. These animal models have enabled a broad study of FM symptoms and mechanisms, as well as new treatment strategies. Current experimental FM models include the reserpine-induced systemic depletion of biogenic amines, muscle application of acid saline, and stress-based (cold, sound, or swim) approaches, among other emerging models. FM models should: (i) mimic the cardinal symptoms and complaints reported by FM patients (e.g., spontaneous nociception, muscle pain, hypersensitivity); (ii) mimic primary comorbidities that can aggravate quality of life and lead to worse outcomes (e.g., fatigue, sleep disturbance, depression, anxiety); (iii) mimic the prevalent pathological mechanisms (e.g., peripheral and central sensitization, inflammation/neuroinflammation, change in the levels of the excitatory and inhibitory neurotransmitters); and (iv) demonstrate a pharmacological profile similar to the clinical treatment of FM. However, it is difficult for any one of these models to include the entire spectrum of clinical FM features once even FM patients are highly heterogeneous. In the past six years (2015 - 2020), a wide range of experimental FM studies has amounted to the literature reinforcing the need for an updated review. Here we have described, in detail, several approaches used to experimentally study FM, with a focus on recent studies in the field and in previously less discussed mechanisms. We highlight each model's challenges, limitations, and future directions, intending to help preclinical researchers establish the correct experimental FM model to use depending on their goals.

Comparable level of aggression between patients with behavioural addiction and healthy subjects

Heightened aggression is identified in several psychiatric disorders, including addiction. In this preliminary study with a relatively small number of samples, aggression in subjects diagnosed with behavioural addiction (BA) was implicitly assessed using the point subtraction aggression paradigm (PSAP) test along with measurements of oxy- and deoxyhaemoglobin dynamics in the prefrontal cortex (PFC) during the test using functional near-infrared spectroscopy. Aggression in BA patients was no higher than that of healthy control (CT) subjects in the PSAP test. Although no apparent increase or decrease in haemoglobin concentrations was observed in the PFC of either BA patients or CT subjects, abnormal correlations within the PFC network were present in BA patients. Consistent with comparable aggression between the groups, blood concentrations of the sex hormone testosterone, which has been shown to be associated with aggressiveness, was even lower in BA patients than in CT subjects. In contrast, when a set of questionnaire surveys for the assessment of aggression were administered, BA patients rated themselves as more aggressive than non-BA subjects. Collectively, these results suggest that aggression may not be heightened in BA, but BA patients may overestimate their aggressiveness, raising concerns about the use of questionnaire surveys for assessments of affective traits such as aggression in behavioural addiction.

Sex Differences in Tolerance to Delta-9-Tetrahydrocannabinol in Mice With Cisplatin-Evoked Chronic Neuropathic Pain

Tolerance to the pain-relieving effects of cannabinoids limits the therapeutic potential of these drugs in patients with chronic pain. Recent preclinical research with rodents and clinical studies in humans has suggested important differences between males and females in the development of tolerance to cannabinoids. Our previous work found that male mice expressing a desensitization resistant form (S426A/S430A) of the type 1 cannabinoid receptor (CB₁R) show delayed tolerance and increased sensitivity to the antinociceptive effects of delta-9-tetrahydrocannabinol (∆⁹-THC). Sex differences in tolerance have been reported in rodent models with females acquiring tolerance to ∆⁹-THC faster than males. However, it remains unknown whether the S426A/S430A mutation alters analgesic tolerance to ∆⁹-THC in mice with chemotherapy-evoked chronic neuropathic pain, and also whether this tolerance might be different between males and females. Male and female S426A/S430A mutant and wild-type littermates were made neuropathic using four once-weekly injections of 5 mg/kg cisplatin and subsequently assessed for tolerance to the anti-allodynic effects of 6 and/or 10 mg/kg ∆⁹-THC. Females acquired tolerance to the anti-allodynic effects of both 6 and 10 mg/kg ∆⁹-THC faster than males. In contrast, the S426A/S430A mutation did not alter tolerance to ∆⁹-THC in either male or female mice. The anti-allodynic effects of ∆⁹-THC were blocked following pretreatment with the CB₁R antagonist, rimonabant, and partially blocked following pretreatment with the CB₂R inverse agonist, SR144528. Our results show that disruption of the GRK/β-arrestin-2 pathway of desensitization did not affect sensitivity and/or tolerance to ∆⁹-THC in a chronic pain model of neuropathy.

High-dose spironolactone lacks effectiveness in treatment of fibromyalgia (RCT)

BACKGROUND

Spironolactone (SPL) is a reversible mineralocorticoid receptor (MR) and androgen receptor (AR) antagonist which attracts pharmacotherapeutic interest not only because of its beneficial effects in heart failure but also because of the pathogenetic roles of MR and AR activities in neuropsychiatric diseases. Recently, beneficial and rapid-onset effects of SPL have been documented in a case series of women with fibromyalgia syndrome (FMS). To reaffirm this observation, we performed a double-blind placebo-controlled randomized clinical trial (RCT).

METHODS

A total of 69 patients were screened, 56 patients were eligible and randomized to SPL or placebo (each n = 28). Forty-three patients completed the clinical trial to the last visit (n = 21 and n = 22). After a run-in phase of 50 and 100 mg/day, 200 mg/day SPL or placebo were applied between days 7 and 28. Primary outcome was the change in the FIQ-G score (Fibromyalgia Impact Questionnaire, German version). Secondary outcome parameters were the changes in pain (numeric rating scale, NRS), mood (ADS), quality of life (SF-36) and change in FIQ scores 14 days after the end of the medication.

RESULTS

SPL of 200 mg/day did not change significantly either the primary or the secondary end points. SPL evoked a transient rise in serum potassium and a transient fall in GFR maximal after 2 weeks, but without clinical relevance.

CONCLUSIONS

SPL at 200 mg/day does not improve symptoms in women with FMS, but was considered not to cause harm.

SIGNIFICANCE

The mineralocorticoid receptor and androgen receptor antagonist spironolactone is repeatedly tested for its therapeutic effectivity against neuropsychiatric disorders. The present RCT demonstrated that 200 mg spironolactone does not change the symptoms of the fibromyalgia syndrome (FMS) in adult women. Between 2 and 4 weeks, spironolactone evokes a transient decrease in GFR and increase in serum potassium. Spironolactone cannot be recommended for the treatment of FMS.

Testosterone protects against the development of widespread muscle pain in mice

Chronic widespread pain conditions are more prevalent in women than men, suggesting a role for gonadal hormones in the observed differences. Previously, we showed that female mice, compared to male, develop widespread, more severe, and longer-duration hyperalgesia in a model of activity-induced muscle pain. We hypothesized testosterone protects males from developing the female pain phenotype. We tested whether orchiectomy of males before induction of an activity-induced pain model produced a female phenotype and whether testosterone administration produced a male phenotype in females. Orchiectomy produced longer-lasting, more widespread hyperalgesia, similar to females. Administration of testosterone to females or orchiectomized males produced unilateral, shorter-lasting hyperalgesia. Prior studies show that the serotonin transporter (SERT) is increased in the nucleus raphe magnus (NRM) in models of chronic pain, and that blockade of SERT in the NRM reduces hyperalgesia. We examined potential sex differences in the distribution of SERT across brain sites involved in nociceptive processing using immunohistochemistry. A sex difference in SERT was found in the NRM in the activity-induced pain model; females had greater SERT immunoreactivity than males. This suggests that testosterone protects against development of widespread, long-lasting muscle pain and that alterations in SERT may underlie the sex differences.

The Relationship Between Androgens and Days per Month of Period Pain, Pelvic Pain, Headache, and TLR4 Responsiveness of Peripheral Blood Mononuclear Cells in Young Women with Dysmenorrhoea

Purpose

Women bear a disproportionate burden of persistent pain conditions when compared to men. To determine whether the hormonal environment affects the clinical experience of pain, as measured by the days per month of pelvic pain (DPelvicPM), period pain (DPeriodPM), headache (DHeadachePM) or the in vitro EC₅₀ for Interleukin-1β (IL-1β) release following TLR4 stimulation with Lipopolysaccharide from Peripheral Blood Mononuclear Cells (PBMCs). Findings were stratified according to use or non-use of the oral contraceptive pill.

Patients and Methods

Fifty-six women aged 16–35 years, with minimal or severe dysmenorrhea, and use or non-use of the OC, were enrolled. Blood was collected on two occasions in a single menstrual cycle: Days 1–2 and Days 7–10. Hormonal analysis for testosterone, dihydrotestosterone, dehydroepiandrosterone, Androstenedione, 3α-Androstanediol, 3β-androstanediol, estradiol, estrone, 17α-hydroxyprogesterone, progesterone, cortisol and sex-hormone binding globulin was undertaken using ultra-sensitive Liquid Chromatography Mass–Spectrometry (LC-MS). PBMCs were exposed to lipopolysaccharide (LPS) and the resulting Interleukin-1β output was determined.

Results

Non-users of the OC showed a strongly inverse correlation between a reducing free androgen index (FAI) and increasing DPelvicPM (p=0.0032), DPeriodPM (p=0.013), DHeadachePM (p=0.041). Non-users of the OC showed a significant increase in DPelvicPM (p=0.049) on Days 7–10. Modestly significant associations were found between reduced androgens and potentiated LPS-induced IL-1β (lower EC₅₀).

Conclusion

This is the first study to investigate the relationship between the hormonal environment and activation of the immune system in young women with dysmenorrhoea-related pain conditions. Low androgen levels were consistently associated with increased pain. Translational implications for the findings are discussed.

Sex-Related Differences in Symptoms and Psychosocial Outcomes in Patients With Fibromyalgia: A Prospective Questionnaire Study

Objective

To investigate sex-related differences in patients with fibromyalgia (FM) in terms of demographic characteristics and clinical features, including tender point count (TPC), mood disorders, sleep problems, FM symptom severity, fatigue, cognitive dysfunction, and quality of life (QOL).

Patients and Methods

We studied 668 consecutive patients with FM (606 women) from May 1, 2012, to November 30, 2013. Validated questionnaires assessed outcomes of depression (Patient Health Questionnaire-9), anxiety (Generalized Anxiety Disorder-7), sleep problems (Medical Outcomes Study Sleep Scale), FM symptom severity (Revised Fibromyalgia Impact Questionnaire), fatigue (Multidimensional Fatigue Inventory), cognitive dysfunction (Multiple Ability Self-report Questionnaire), and QOL (36-Item Short Form Health Survey). Nonparametric Mann-Whitney U and Pearson χ² tests were used to compare continuous and categorical outcome measures, respectively, between men and women. Linear regression models were performed for all continuous dependent variables, adjusting for age, body mass index, ethnicity, marital status, and highest education level completed. P<.05 was considered statistically significant. The Benjamini-Hochberg procedure was used to adjust for multiple comparisons.

Results

Multiple linear regression analysis revealed a significant association of female sex and greater TPC (P<.001), lower overall FM symptom severity (lower overall Revised Fibromyalgia Impact Questionnaire score; P=.03), and higher QOL subscale score for vitality (36-Item Short Form Health Survey vitality subscale score; P=.02). After adjustment for multiple comparisons, only the association between female sex and greater TPC remained significant. There were no sex-related differences in demographic characteristics, depression, anxiety, sleep problems, FM symptom severity, cognitive dysfunction, and QOL.

Conclusion

A higher TPC may be associated with female sex in patients with FM. The assumption of other sex-based differences in the clinical presentation of FM was not supported in our study.

Pain and Cortisol in Patients with Fibromyalgia: Systematic Review and Meta-Analysis

This systematic review and meta-analysis sought to gain further insight into the relationship between cortisol reactivity and chronic widespread pain in patients with fibromyalgia. The studies selected were those conducted in adults with fibromyalgia that were random controlled, non-controlled or observational. Studies were excluded if they examined diseases other than fibromyalgia or if they did not report on pain or cortisol. Twelve studies met inclusion criteria. Data were extracted into tabular format using predefined data fields by two reviewers and assessed for accuracy by a third reviewer. The methodological quality of the studies was assessed using the PEDro scale. Data Synthesis: Of 263 studies identified, 12 were selected for our review and 10 were finally included as their methodological quality was good. In the meta-analysis, we calculated effect sizes of interventions on pain indicators and cortisol levels in patients with fibromyalgia. A small overall effect of all the interventions was observed on pain tolerance and pressure pain thresholds, yet this effect lacked significance (ES = 0.150; 95%CI 0.932–1.550; p > 0.05). Conclusions: While some effects of individual nonpharmacological therapeutic interventions were observed on both cortisol levels and measures of pain, our results suggest much further work is needed to elucidate the true relationship between chronic widespread pain and cortisol levels in patients with fibromyalgia.

Postmenopausal women with irritable bowel syndrome (IBS) have more severe symptoms than premenopausal women with IBS

BACKGROUND

Although irritable bowel syndrome (IBS) is more common in women, little is known about the role of hormonal changes and menopause in IBS. This study aimed to evaluate for differences in gastrointestinal (GI) and psychological symptoms between pre- and postmenopausal women with IBS compared to age-matched men with IBS.

METHODS

Patients with Rome-positive IBS were identified. Premenopausal women were <45 years of age with regular menses. Postmenopausal women were ≥45 years without menses for at least 1 year. Younger men were <45 years, and older men were ≥45 years. Questionnaires measured severity of IBS symptoms, somatic symptoms, health-related quality of life (HRQOL), and psychological symptoms. Multivariable linear or logistic regressions evaluating relationships between age and sex were performed.

KEY RESULTS

190 premenopausal women (mean age 30.25 years), 52 postmenopausal women (mean age 54.38 years), 190 men <45 years (mean age 30.45 years), and 52 men ≥45 years (mean age 53.37 years) were included. Postmenopausal IBS women had greater severity of IBS symptoms (P = .003) and worse physical HRQOL (P = .048) compared to premenopausal women. No differences were observed between age-matched older and younger IBS men. Constipation increased with age for both sexes but was the principal IBS subtype in women only.

CONCLUSIONS AND INFERENCES

Postmenopausal women with IBS have more severe IBS symptoms than premenopausal women, while no comparable age-related changes were seen in IBS men. The modulatory effect of female sex hormones on brain-gut interactions which affect visceral perception and GI function likely contributes to these findings.

The gender context of pain

Pain is a major source of global suffering, with women bearing the greatest burden. Alongside biology, psychological and social factors, including gender, help explain these differences. However, there has been no direct attempt to develop a unified social psychological model of men and women's pain. By drawing on approaches to both gender and pain, a gender context model of pain is presented. It proposes that pain is partly influenced by the gender context in which it occurs, which operates at both individual and interpersonal levels. The model is used to structure an appraisal of the existing evidence around gender and pain, and explore whether the model helps explain why such variation occurs. It is argued that despite evidence for an association between gender and pain, there are empirical gaps that need to be addressed. Implications and directions for future investigations into sex, gender and pain are considered.

Possible Molecular Mediators Involved and Mechanistic Insight into Fibromyalgia and Associated Co-morbidities

Fibromyalgia is a chronic complex syndrome of non-articulate origin characterized by musculoskeletal pain, painful tender points, sleep problems and co-morbidities including depression, migraine. The etiopathogenesis of fibromyalgia is complex, variable and remains inconclusive. The etiological factors that have been defined include stress, genetic predisposition and environmental components. As per the reports of the American College of Rheumatology (ACR) the prevalence of fibromyalgia varies from 2 to 22% among the general population with poor diagnostic features primarily pain. Fibromyalgia encompasses a spectrum of co-morbid conditions with multifarious pathogenesis. The highly prevalent manifestations of fibromyalgia include heterogeneous pain and aches. Biochemical and neurobiological elements of fibromyalgia include neurotransmitters, hypothalamic pituitary adrenal axis (HPA axis), inflammatory cytokines, monoaminergic pathway, opioid peptides, sex hormones, nerve growth factor (NGF) and local free radical insult. An imbalance in the serotonergic system is the major underlying etiological factor that has been explored most widely. Owing to complex interplay of diverse pathophysiological pathways, overlapping co-morbidities such as depression have been clinically observed. Therapeutic management of fibromyalgia involves both non pharmacological and pharmacological measures. The current review presents various dysregulations and their association with symptoms of fibromyalgia along with their underlying neurobiological aspects.

TRP Channels as Potential Targets for Sex-Related Differences in Migraine Pain

Chronic pain is one of the most debilitating human diseases and represents a social and economic burden for our society. Great efforts are being made to understand the molecular and cellular mechanisms underlying the pathophysiology of pain transduction. It is particularly noteworthy that some types of chronic pain, such as migraine, display a remarkable sex dimorphism, being up to three times more prevalent in women than in men. This gender prevalence in migraine appears to be related to sex differences arising from both gonadal and genetic factors. Indeed, the functionality of the somatosensory, immune, and endothelial systems seems modulated by sex hormones, as well as by X-linked genes differentially expressed during development. Here, we review the current data on the modulation of the somatosensory system functionality by gonadal hormones. Although this is still an area that requires intense investigation, there is evidence suggesting a direct regulation of nociceptor activity by sex hormones at the transcriptional, translational, and functional levels. Data are being accumulated on the effect of sex hormones on TRP channels such as TRPV1 that make pivotal contributions to nociceptor excitability and sensitization in migraine and other chronic pain syndromes. These data suggest that modulation of TRP channels' expression and/or activity by gonadal hormones provide novel pathways for drug intervention that may be useful for targeting the sex dimorphism observed in migraine.

"Luteal Analgesia": Progesterone Dissociates Pain Intensity and Unpleasantness by Influencing Emotion Regulation Networks

Background: Pregnancy-induced analgesia is known to occur in association with the very high levels of estradiol and progesterone circulating during pregnancy. In women with natural ovulatory menstrual cycles, more modest rises in these hormones occur on a monthly basis. We therefore hypothesized that the high estradiol high progesterone state indicative of ovulation would be associated with a reduction in the pain experience. Methods: We used fMRI and a noxious thermal stimulus to explore the relationship between sex steroid hormones and the pain experience. Specifically, we assessed the relationship with stimulus-related activity in key regions of networks involved in emotion regulation, and functional connectivity between these regions. Results: We demonstrate that physiologically high progesterone levels are associated with a reduction in the affective component of the pain experience and a dissociation between pain intensity and unpleasantness. This dissociation is related to decreased functional connectivity between the inferior frontal gyrus and amygdala. Moreover, we have shown that in the pre-ovulatory state, the traditionally "male" sex hormone, testosterone, is the strongest hormonal regulator of pain-related activity and connectivity within the emotional regulation network. However, following ovulation the traditionally "female" sex hormones, estradiol and progesterone, appear to dominate. Conclusions: We propose that a phenomenon of "luteal analgesia" exists with potential reproductive advantages.