Influence of estrogen levels on thermal perception, pain thresholds, and pain tolerance: studies on women undergoing in vitro fertilization

Are there sex differences in risk for exertional heat stroke? A translational approach

NEW FINDINGS

What is the topic of this review? This review discusses the current status of the literature in sex differences in exertional heat stroke. What advances does this review highlight? We utilize a translational model to explore possible physical and physiological differences with respect risk and treatment of exertional heat stroke.

ABSTRACT

Exertional heat stroke (EHS) is a potentially fatal condition brought about by a combination of physical activity and heat stress and resulting in central nervous system dysfunction and organ damage. EHS impacts several hundred individuals each year ranging from military personnel, athletes, to occupational workers. Understanding the pathophysiology and risk factors can aid in reducing EHS across the globe. While we know there are differences between sexes in mechanisms of thermoregulation, there is currently not a clear understanding if/how those differences impact EHS risk. The purpose of this review is to assess the current status of the literature surrounding EHS from risk factors to treatment using both animal and human models. We use a translational approach, considering both animal and human research to elucidate the possible influence of female sex hormones on temperature regulation and performance in the heat and highlight the specific areas with limited research. While more work is necessary to comprehensively understand these differences, the current research presented provides a good framework for future investigations. This article is protected by copyright. All rights reserved.

Why do women choose to undergo oocyte aspiration without sedation or analgesia?

Objective

Oocyte pick-up (OPU) is a painful but essential part of in-vitro fertilization (IVF) that is usually performed under sedation and analgesia (SaA). Our aim was to study that why some women decide to undergo OPU without SaA?

Methods

This was a prospective study using patient questionnaires and the standardized 7-item generalized anxiety disorder (GAD-7) score. The patients were asked to assess the pain experienced during OPU using a visual analog scale (VAS). The study sample was a convenience sample of 100 healthy women undergoing OPU at our unit with or without SaA.

Results

Women who chose to undergo OPU without SaA were significantly more likely to express the fear of anesthesia. A high pain score (VAS ≥ 6) was reported by significantly more patients who underwent OPU without SaA than with SaA. Yet, 98% of the patients who underwent OPU without SaA stated that in future IVF cycles, they would still choose to undergo OPU without SaA. More patients had high anxiety scores among those who underwent OPU with than without SaA.

Conclusions

Women who chose to undergo OPU without SaA reported more often fear of anesthesia. Although these women experienced significantly more pain during OPU, almost all of them suggested that they would still choose to undergo OPU without SaA. Increased anxiety, as expressed by higher GAD-7 scores, was not associated with a tendency to choose SaA during OPU. The option of OPU without SaA seems to be an acceptable option for selected women.

Lay summary

Egg retrieval from the ovaries is a painful part of in vitro fertilization (IVF). It is, therefore, usually performed under sedation and pain relief (analgesia). The aim of this study was to investigate: Why some women decide to undergo egg retrieval without sedation? We prospectively studied 100 women using patient questionnaires and standardized scores in order to measure patient's pain and anxiety levels. We found that women who chose to undergo egg retrieval without sedation were significantly more likely to express fear of anesthesia. As expected, women who decided to forgo sedation experienced more pain during egg retrieval, yet, 98% of them decided that in future IVF cycles, they would still choose to undergo egg retrieval without sedation. Surprisingly, women who had high anxiety scores were not more likely to ask for sedation during egg retrieval. The option to undergo egg retrieval without sedation during IVF seems to be acceptable for some women.

Involvement of glutamate receptors of the paragigantocellularis lateralis nucleus in the pain modulatory effect of 17β-estradiol in male rats

The pain modulatory role of the paragigantocellularis lateralis nucleus (LPGi) and the 17β-estradiol has thoroughly been probed. This study investigates the contribution of ionotropic glutamate receptors in pain modulatory effect of intra-LPGi injection of 17β-estradiol. For this purpose, the LPGi nucleus cannulation was performed and drugs were injected into this nucleus, 15 min prior to the formalin test. The duration of formalin-induced flexing and licking behaviors was recorded for 60 min immediately after formalin injection. The results showed that the flexing behavior is significantly decreased by intra-LPGi injection of 0.8 µmol 17β-estradiol duringboth phases of formalin test (P < 0.001). However, 17β-estradiol attenuated the licking duration only in the second phase (P < 0.001). Interestingly, NMDA and AMPA/kainate receptor antagonists (AP5 and CNQX, respectively) significantly counteracted the analgesic effect of intra-LPGi injection of 17β-estradiol in both phases of the formalin test (P < 0.001). Consequently, the revealing results showed that the analgesic effect of intra-LPGi injection of 17β-estradiol on acute inflammatory pain might be mediated via the activation of ionotropic glutamate receptors.

Oral contraceptive use and its association with symptomatology in migraine patients

Background:

Hormonal changes in natural menstrual cycles are known to modulate and even worsen headache symptoms in migraineurs; however, the impact of oral contraceptive pills (OCP), including combined oral contraceptive (COC) and progestogen-only pills on migraine symptomatology, is little investigated.

Method:

In this retrospective cohort study of 1758 migraine patients, data from 1032 female patients aged 15–45 years were accessed and their contraceptive methods, if any, were analyzed. Further comparisons were conducted between patients with OCP use and those without OCP use regarding the demographics, headache symptoms, and associated symptoms. Most OCP users in this study were assumed to have used COC, but information of individual hormone content of OCP was not collected. Patients with nonoral hormonal contraceptives were excluded for further comparison.

Results:

The use of OCP was common (47.8%) among the study cohort. Compared to those without OCP use ( n = 410), patients with OCP use ( n = 493) were younger (27.4 ± 7.0 vs. 32.8 ± 7.9, p < 0.001), had lower headache frequency (days per month, 11.1 ± 7.5 vs. 12.3 ± 8.8, p = 0.03), were less likely to have osmophobia (47.3 vs. 54.4%, p = 0.033) or cranial autonomic symptoms (44.8 vs. 53.2%, p = 0.013), and more commonly reported menstrually-related worsening of headache (52.3 vs. 42.4%, p = 0.012). The proportion of migraine with aura or other headache characteristics including severity, unilaterality, and pulsatile characteristic showed no differences between groups.

Conclusion:

Our data provide real-life information about contraceptive use among patients with migraine. The use of OCP is associated with differences in migraine symptomatology. Further studies are needed to determine whether this relationship is causal and any possible underlying mechanism.

Hypothesis regarding the effects of gonadotropins on the level of free fatty acids and phospholipids in serum and follicular fluid during controlled ovarian stimulation

Controlled ovarian stimulation (COS) is used to augment the number of retrieved oocytes in in vitro fertilization (IVF). Follicular fluid (FF) contributes significantly to oocyte quality. Since the FF is composed of follicular secretions and plasma exudation, it reflects alterations in granulosa and thecal cells secretion as well as changes in the level of plasma constituents. Phospholipids (PL) and free fatty acids (FFA) are important constituents of both, FF and serum. Our hypothesis is that COS affects the level of PL and FFA in serum. Furthermore, since the level of PL and FFA in FF partially depends on their levels in serum, as a collaterally of our hypothesis is that the existing level of PL and FFA in serum correlates with the levels of PL and FFA in FF, and that the dose of applied gonadotropins during COS will correlate with the levels of PL and FFA in serum and FF. In addition, we assume that the level of PL and FFA in serum and in FF after COS will correlate with the retrieved number of GQ oocytes, one of the most important outcomes of COS. .

Burning mouth syndrome in postmenopausal women with self-reported sleep problems

OBJECTIVE

The aim of this study was to investigate possible relationships among hematologic factors, psychological dimensions, the presence of self-reported sleep problems, and clinical characteristics in patients with burning mouth syndrome (BMS).

METHODS

Twenty-five postmenopausal female patients with primary BMS (aged 55.2 ± 9.6 years) were included. All participants underwent clinical and psychological evaluations and blood sampling. The patients were subdivided according to the absence or presence of the self-reported sleep problems.

RESULTS

Pain intensity of BMS patients with sleep problems was significantly higher than those without sleep problems, and the severity of oral complaints was correlated with the presence of depression, anxiety, hostility, phobia, and psychosis. Estradiol levels were significantly lower, and FSH and LH levels were higher in BMS patients with sleep problems than those without sleep problems.

DISCUSSION

BMS patients with sleep problems may suffer inharmonious psychoneuroendocrinological interactions that might worsen oral BMS symptoms.

An Investigation of the Effects of Testosterone and Behavioral Expressions of Pain on Sex/Gender Differences in Pain Perception

Research indicates that women are more susceptible to pain than men, but the reason for this difference is unclear. While estrogen and progesterone have been implicated, testosterone has not received adequate consideration in the literature. Additionally, incorporating behavioral expressions, or exaggerations, of pain as an important aspect of pain perception is receiving increasing attention. The current study examined the role of testosterone in female pain expression and perception via the cold pressor test. Following all participant exclusions, 46 healthy participants (32 women) provided saliva samples for testosterone analysis using enzyme-linked immunosorbent assay before and after rating their pain during the cold pressor test. Participants used a visual analog scale to indicate how the 2℃ water was perceived, ranging from “worst pain imaginable” to “no pain.” The researcher also noted whether a participant displayed overt behavioral expressions of pain such as jumping and cursing. The results revealed that men reported lower visual analog scale scores than women, indicating less perceived pain. A subgroup of women who displayed overt behavioral responses to pain seemed to be driving this sex/gender difference. It was expected that this subgroup of females would have corresponding changes in testosterone that would further explain the observed sex/gender differences, but this was not supported. Collectively, these data add to the previous literature investigating sex/gender differences in pain perception and highlight the importance of studying overt behavioral expressions of pain. Testosterone may alter this behavior and subsequent pain perception, but the contributions of testosterone are likely subtle and were not detected in this study.

Thermal pain tolerance and pain rating in normal subjects: Gender and age effects

BACKGROUND

Thermal detection thresholds and thermal pain thresholds are important in quantitative sensory testing. Although they have been well studied for assessing somatosensory function, the investigation of thermal pain tolerance has been insufficient. The aim of this study was to explore the characteristics of thermal pain tolerance and pain ratings in healthy subjects.

METHODS

Cold pain tolerance (CPTol) and heat pain tolerance (HPTol) were tested in 213 healthy adults aged 18-81 years recruited from the local community. The thermal detection and thermal pain thresholds were also tested to investigate the association with pain tolerance. The visual analogue scale (VAS) was used for assessing pain severity immediately after the thermal pain and tolerance tests.

RESULTS

The normality of the CPTol and HPTol was acceptable. Most participants rated the pain induced by the CPTol and HPTol testing as moderate. HPTol was lower in women than in men (p = 0.001), but CPTol did not differ between sexes. The pain ratings of CPTol and HPTol did not differ between sexes, but significant age effects were observed. The association of the tolerance temperature with pain ratings was weak, while those of pain ratings for CPTol and HPTol were strong (r = 0.87).

CONCLUSIONS

Women were more sensitive to tolerance heat pain stimuli. Younger participants reported more pain for thermal pain and tolerance tests.

SIGNIFICANCE

Thermal pain tolerance and pain rating for the thermal pain tolerance temperature depend on gender and age. Women are more sensitive to heat temperatures, young people rate more pain, and the pain ratings of heat and cold are strongly correlated.

Association between estrogen levels and temporomandibular disorders: a systematic literature review

Introduction

To evaluate whether the hypothesis that estrogen levels are associated with temporomandibular disorders (TMD) in humans can be confirmed or contradicted by available literature.

Material and methods

A systematic review based on the content of PubMed, Scopus, and Cochrane Library databases was performed. Studies were identified using a combination of key words ‘temporomandibular disorder’ and ‘estrogen’. Nine studies were included into our review.

Results

The relationship between estrogen levels and TMD was found in seven out of nine reviewed papers. Results from two papers suggest that a high estrogen level is associated with an increased prevalence of TMD. Five additional papers found a relationship between a low estrogen level and an increase in TMD pain. In considering the value of evidence and inconsistencies of results in the reviewed publications, we state that there is weak evidence to support the hypothesis that estrogen levels are associated with TMD.

Conclusions

Results of reviewed studies were divergent and sometimes contradictory. One possible explanation is that estrogen influences TMD pain processing differently than temporomandibular joints (TMJ) structures, as shown in many animal studies. Estrogen may influence TMD pain processing differently than TMJ structures. We suggest consideration of the dual action of estrogen when planning future studies on its association with TMD.

Low-dose progestin-releasing contraceptives are associated with a higher pain threshold in healthy women

OBJECTIVE

To determine the pain thresholds of women taking different formulations of hormonal contraceptives.

DESIGN

Cross-sectional study.

SETTING

Basic health care unit.

PATIENT(S)

Eighty-nine healthy nonusers and 188 users of hormonal contraceptives.

INTERVENTION(S)

Subject interviews were followed by the application of a semistructured questionnaire, including a psychometric assessment with the Beck Depression Inventory and the State-Trait Anxiety Inventory. After the interview, a 10-mL peripheral blood sample was collected. Pain thresholds were obtained by performing pressure algometry.

MAIN OUTCOME MEASURE(S)

Serum concentrations of E2, P, and T (free fraction) were determined via chemoluminescence. The menstrual cycle phase was determined according to hormonal level and identification of an LH surge in urine. Pain threshold was evaluated with a dynamometer applied to the forearm skin of the nondominant limb and abdominal wall.

RESULT(S)

Progestin-only contraceptive users showed a higher pain pressure threshold in the forearm (2.94 ± 0.96 vs. 2.74 ± 0.89 vs. 2.62 ± 0.92) and right (2.11 ± 0.87 vs. 1.83 ± 0.81 vs. 1.78 ± 0.77) and left abdomen (2.12 ± 0.88 vs. 1.79 ± 0.76 vs. 1.73 ± 0.70) than did combined hormonal contraceptive users and nonusers of hormonal contraceptives, respectively. Users of contraceptives that continuously release etonogestrel (subcutaneous implant, vaginal ring) or levonorgestrel (intrauterine devices) had higher pain thresholds.

CONCLUSION(S)

Women who used hormonal contraceptives enabling continuous release of etonogestrel or levonorgestrel tended to have higher pain thresholds than did nonusers of hormonal contraceptives.

Prevalence of signs and symptoms indicative of temporomandibular disorders and headaches in 35-, 50-, 65- and 75-year-olds living in Västerbotten, Sweden

OBJECTIVE

The aim of this study was to analyze and compare prevalence of signs and frequently occurring symptoms indicative of temporomandibular disorder (TMD) and headaches in 35-, 50-, 65- and 75-year-old men and women in Västerbotten County, Sweden.

MATERIALS AND METHODS

From a total target population of 11 324 subjects living in Västerbotten County in the year 2002, 300 individuals in each age group were randomly selected. Of these, 998 (82% response rate) answered and returned a postal questionnaire and 779 (65% response rate) individuals accepted a clinical examination.

RESULTS

The prevalence of frequent TMD symptoms peaked among 50-year-old women and then declined. Women at this age reported significantly higher prevalence compared to men for all TMD symptoms except temporomandibular joint locking. In the 65- and 75-year-olds, the prevalence was practically equal between men and women as well as between these ages. Frequent headaches showed the highest prevalence among 35- and 50-year-old women, with a statistically significant difference between men and women of 50 years of age (p < 0.05). Fifty-year-old women had statistically significantly higher prevalence of muscle pain to palpation (p < 0.001), temporomandibular joint sounds (p < 0.01) and impaired maximal jaw opening capacity (p < 0.01), compared to 50-year-old men.

CONCLUSIONS

The different symptoms indicative of TMD and headaches showed a similar pattern, with higher prevalence among the 35- and 50-year-old, as compared to the 65- and 75-year-old, participants. The pattern may be related to biological, psychosocial or generation-related factors.

Estrogenic influences in pain processing

Gonadal hormones not only play a pivotal role in reproductive behavior and sexual differentiation, they also contribute to thermoregulation, feeding, memory, neuronal survival, and the perception of somatosensory stimuli. Numerous studies on both animals and human subjects have also demonstrated the potential effects of gonadal hormones, such as estrogens, on pain transmission. These effects most likely involve multiple neuroanatomical circuits as well as diverse neurochemical systems and they therefore need to be evaluated specifically to determine the localization and intrinsic characteristics of the neurons engaged. The aim of this review is to summarize the morphological as well as biochemical evidence in support for gonadal hormone modulation of nociceptive processing, with particular focus on estrogens and spinal cord mechanisms.

Transdermal hormonal therapy in perimenstrual migraine: why, when and how?

Experimental and clinical evidence is strongly in favor of a role for estrogens in migraine. It is clear that estrogen fluctuations represent trigger factors for the attacks, while the resolution of these fluctuations (menopause) may be associated to the remission or, conversely, to the worsening of the disease. However, the exact mechanisms and mediators underlying the effects of estrogens in migraine are largely unknown. The exact mechanisms and mediators underlying the effects of estrogens in migraine are largely unknown. In this review, we summarize clinical and preclinical data that are relevant for the role of estrogens in migraine and we discuss how estrogen modulation can be exploited positively to improve hormonal-related migraine.

Importance of sex to pain and its amelioration; relevance of spinal estrogens and its membrane receptors

Estrogens have a multitude of effects on opioid systems and are thought to play a key role in sexually dimorphic nociception and opioid antinociception. Heretofore, classical genomic actions of estrogens are largely thought to be responsible for the effects of these steroids on nociception and opioid antinociception. The recent discovery that estrogens can also activate estrogen receptors that are located in the plasma membrane, the effects of which are manifest in seconds to minutes instead of hours to days has revolutionized our thinking concerning the ways in which estrogens are likely to modulate pain responsiveness and the dynamic nature of that modulation. This review summarizes parameters of opioid functionality and nociception that are subject to modulation by estrogens, underscoring the added dimensions of such modulation that accrues from rapid membrane estrogen receptor signaling. Implications of this mode of signaling regarding putative sources of estrogens and its degradation are also discussed.

Prediction of pain sensitivity in healthy volunteers

PURPOSE

The primary objective of the present study was to evaluate predictive parameters of the acute pain score during induction of an inflammatory heat injury.

PATIENTS AND METHODS

Healthy volunteers (50 females/50 males) were included in the study. The predictive potential of gender, anthropometric (body surface area, body mass index), psychological (anxiety, depression, vulnerability), and psychophysical (quantitative sensory testing, conditioned pain modulation) variables in estimating the pain response to a validated heat injury (47°C, 7 minutes, area 12.5 cm(2)) were investigated. All assessments were made in duplicate sessions separated by 21 days (median).

RESULTS

There were three main findings in this study. First, a predictive model of pain sensitivity during the heat injury, including both genders and using multiple regression technique, could account for 28% of the variance (P < 0.0001), but gender-related differences in the final model could not be demonstrated. Second, the results confirmed significant gender-related differences in perception of electrical, pressure, and cold pressor stimuli (P < 0.002). Third, positive correlations between anthropometric data and pain perception during electrical and pressure stimuli were demonstrated (P < 0.001 and P < 0.005, respectively).

CONCLUSION

The study demonstrated predictability of acute pain sensitivity, and although gender-related differences in pain perception were demonstrated, no gender-related differences in pain sensitivity could be shown. Interestingly, positive correlations between anthropometric data and pain perception were shown for the first time.