Thermoregulatory Physiology of Menopausal Hot Flashes a Review
Abstract
Hot flashes proceed to exist a troublesome problem for menopausal women the earth over. After >50 y of research, we still do not understand the etiology and mechanism of hot flashes, nor exercise we know how estrogen, the major pharmaceutical treatment, works to reduce hot flashes. We are gaining insight into sociocultural complexities that may touch on how and whether women written report hot flashes. And nosotros are becoming more sophisticated in our enquiry tools (be it questionnaires, physiological monitors, or brain imaging techniques). New aspects of hot flash enquiry, including neuroimaging and the written report of genetic polymorphisms, when combined with increasingly nuanced ways of request questions of culturally singled-out populations, provide challenges but rich complexity from which a better understanding will emerge.
Introduction
Hot flashes are 1 of the most common symptoms experienced by women around the world during the transition to and through menopause. Whereas prevalence rates tend to be higher in Western countries than, due east.g., in Asian countries, rates vary widely and are likely influenced by a range of factors (1). In the U.S., hot flashes are 1 of the principal reasons women at menopause seek medical help or look for dietary supplements and over-the-counter remedies for relief (2,three). In 2002, after publication of the results from the large NIH-funded Women'south Health Initiative study, which indicated that estrogen was harmful on a number of indices, many women stopped taking this hormone therapy (four) and for >30%, bothersome, often astringent hot flashes returned (5). These women re-experienced hot flashes they thought they had left far backside. Notwithstanding, while women have complained of these "spells" of heat awareness from fourth dimension immemorial and despite this considerable public health problem, at the start of the 21st century, nosotros still do non understand the etiology or physiology, nor practice we know how the most widely used pharmaceutical treatment to date, estrogen, works to relieve hot flashes.
This artice aims to provide a brief overview of some aspects of the biology of hot flashes and methods used in research, given insights nosotros at present have into biosociocultural factors that influence how nosotros observe and the miracle being observed. Emerging areas of research are also discussed.
Hot flashes: the phenomenon
The terms hot flash and hot affluent are used interchangeably and are typically synonymous, referring to a sudden sensation of rut and sweating, nigh notably on the upper torso. Hot flashes occur primarily and most intensively in peri- and postmenopausal women. They likewise may occur when estrogen drops suddenly and rapidly, such equally later removal of the ovaries of premenopausal women, with chemically induced menopause, and also in breast cancer patients treated with selective estrogen receptor modifiers such as tamoxifen. Men can experience hot flashes, particularly when testosterone levels autumn chop-chop, such every bit in men with prostate cancer treated medically or surgically. In both women and men, these are situations where there is an abrupt drop in sex steroid hormones, resulting in hot flashes.
Hot flashes can occur twenty-four hour period or night; when they occur at night, they are called night sweats. Each particular episode lasts between 3 and ten min and can recur with varying frequency (6). Some women experience hot flashes hourly or daily, while for others they may occur just occasionally; a small per centum of women report not having any hot flashes. Whether this is a affair of a threshold of perception or there are genetic, environmental, or lifestyle factors that prevent hot flashes is a field of study of increasing interest.
Although for most women, hot flashes brainstorm and have their acme occurrence during the peri- and early on postmenopausal periods, typically when a woman is in her belatedly 40s and early on 50s, at times they may begin when menstrual cycles are still regular (vi). The majority of women take hot flashes for a twelvemonth or two, but ∼15% may accept them nonstop for x, twenty, or 30 y (vi). And while every adult female's estrogen level decreases during the transition to and through menopause, it remains an enigma as to why some women's bodies seem to arrange and hot flashes taper off, while others go on having hot flashes for many years. In addition, for some women whose hot flashes were treated successfully past estrogen, the hot flashes resume subsequently cessation of estrogen handling.
Physiological changes during a hot flash
Thermography provides a visual snapshot of the skin surface manifestation of the design of thermoregulatory changes during a hot wink and provides insights into underlying physiological changes ( Supplemental Fig. one ). One can see the pare areas that warm during the hot flash (fingers, neck, face up) and cool as the hot flash subsides.
Effigy 1 graphically illustrates some of the primary physiological changes that occur during a hot wink (7). "Sensation" is a subjective rating of the sense of hot flash intensity on a scale of 0–10 (10 being the virtually intense). At the onset of a hot flash, there is a sudden increment in sweating. Heart rate increases anywhere from v to 25 beats/min. Cutaneous vasodilation occurs and blood menses to the skin increases, evident in an increase in finger pare temperature. With the sudden and rapid increment in heat loss (sweating and cutaneous vasodilation), internal body temperature drops. The forehead temperature also cools given the sweating and subsequent evaporative cooling that occurs. These physiological phenomena can exist reliably measured in the laboratory (Fig. 2) (7,8). These are labor-intensive studies and are not appropriate for clinical trials of various hot flash treatments that involve ambulatory, gratis living individuals. For this purpose, portable monitors that record changes in sweating, equally measured by changes in the electric electrical conductivity of the peel (skin conductance), are used to correlate subjective reports of hot flash occurrence with this objective physiological change.
FIGURE 1
Physiological changes during a hot wink. Characteristic physiological changes during a hot wink: sensation (SENS), eye rate, internal body temperature (Teso = esophageal), pare temperatures (Tfor = brow, Tfin = finger), and ambient temperature (Ta = ambient). Reproduced from Kronenberg and Downey (seven) ©ã 2008 NRC Canada or its licensors. Reproduced with permission.
FIGURE 1
Physiological changes during a hot flash. Characteristic physiological changes during a hot wink: sensation (SENS), heart rate, internal body temperature (Teso = esophageal), skin temperatures (Tfor = forehead, Tfin = finger), and ambient temperature (Ta = ambient). Reproduced from Kronenberg and Downey (vii) ©ã 2008 NRC Canada or its licensors. Reproduced with permission.
FIGURE ii
Multiple hot flashes: physiological changes. Sensation (SENS), heart rate, finger claret menstruum, forearm sweating rate, internal body temperature (Teso = esophageal), skin temperatures (Tfor = forehead, Tfin = finger) and ambient temperature (Ta = ambience). Adapted from Kronenberg and Downey (seven). ©ã 2008 NRC Canada or its licensors. Reproduced with permission.
Effigy 2
Multiple hot flashes: physiological changes. Awareness (SENS), heart rate, finger blood period, forearm sweating rate, internal trunk temperature (Teso = esophageal), peel temperatures (Tfor = forehead, Tfin = finger) and ambient temperature (Ta = ambient). Adapted from Kronenberg and Downey (seven). ©ã 2008 NRC Canada or its licensors. Reproduced with permission.
Mechanisms of hot flashes
Estrogen has been studied and used to treat hot flashes for >60 y, but the mechanism by which it works is all the same in question. This is due to relatively little examination of basic hot flash physiology, which has not received the inquiry attention that has been accorded clinical trials of therapeutic agents. Thus, the body of knowledge on the endocrinology, neurophysiology, thermoregulatory physiology, and other aspects of hot flash biology is limited.
One long-standing supposition has been that hot flashes involve transient dysregulation of the thermoregulatory system, triggering homeostatic heat loss mechanisms to render the system to normal. During a hot flash, many of the easily observed physiological changes involve the thermoregulatory and vascular systems. This remains an area of incomplete research.
Conspicuously, estrogen plays some role as a mediator of hot flashes. Hot flashes occur as estrogen levels decline and they are alleviated for the most office by treatment with estrogen (9). Estrogen priming is likely important. Young women with low estrogen levels do not take hot flashes, but if given estrogen and then withdrawn from information technology, they volition take hot flashes. And premenopausal women whose ovaries are removed most often feel hot flashes about immediately. However, low estrogen levels alone do non explain the presence of hot flashes. Investigators have searched for correlations between estrogen levels and the occurrence of hot flashes in women with and without hot flashes too as with individual hot flashes with conflicting results. Some population studies take demonstrated inverse relationships between estrogen levels and hot flashes (10,11), as have more contempo studies (12). Others, including Freedman et al. (13), have non corroborated these results when small groups of symptomatic and asymptomatic women were compared.
There has been test of the levels of circulating hormones, including sex steroids and gonadotropins, among others. Substances such as luteinizing hormone (14,15), B-endorphin, adrenocorticotropic hormone (16), and others show pulsatile action that is temporally correlated with hot wink occurrence, only not causally related (7). Freedman et al. (17) accept proposed, based on several studies, that elevated brain norepinephrine plays a office in the etiology of hot flashes. Examining the complex interactions of the multiple systems that are involved has non been substantively undertaken. Thus, at this time, there is no definitive decision of what it is that triggers private hot flashes or explains why some women do or do not experience them.
Sociocultural issues in measuring hot flashes
Hot flashes occur worldwide, and starting in the 1970s, inquiry documenting such occurrence increased substantially. A wide distribution of the prevalence of hot flashes around the globe continues to be examined, with reports, particularly in Asian countries, of prevalence less than that in the Usa and other Western countries (1,18). Interest in understanding these differences has raised questions nearly whether these differences are due to genetic, cultural, environmental, or lifestyle factors such as diet and exercise.
Research in Japan has provided detail insight. Japanese women have a high dietary intake of soy (relative to Western countries) and it was hypothesized that this might explain why they have fewer hot flashes than women in the US, Canada, and Europe. Bones scientific discipline research has established that isoflavones (compounds in soy and other plants) accept estrogen-like activity (19). Involvement in the relationship between the soy consumption of different populations and hot wink prevalence led to epidemiological studies comparing level of dietary soy intake and frequency of hot flashes in countries such as Nippon, where an inverse association between soy intake and hot flashes has been demonstrated (20,21). Clinical studies of soy foods and soy isoflavones to treat hot flashes proliferated, with mixed results, although there was a tendency toward a beneficial effect (22).
Yet, information technology is at present known that at that place are confounding factors that make this a more circuitous effect and might contribute to explaining the differing results among the clinical trials. The isoflavone daidzein is biotransformed by intestinal microflora to the active metabolite, equol. The presence of the item bacterial species responsible for this conversion differs among people in different countries and thus some people are "equol producers" and some are not (19,23).
Farther complexity may relate to a critical period for soy consumption relative to its beneficial health effects. This has come to lite while trying to understand the observation of lower breast cancer rates in populations with high soy food consumption. Exposure during adulthood did not back up these observations. Information are accumulating to support a protective effect of soy when information technology is consumed during early life (childhood/boyhood) with regard to breast cancer afterward in life (24). Soy foods are a staple in Asian cuisine and are consumed throughout life, suggesting their role in breast cancer prevention. Consumption of soy or genistein affects gene expression and activates estrogen receptor α, thereby affecting BRCA1 (25,26). Similarly, information technology is possible that consuming soy during puberty may affect whether i experiences hot flashes during menopause; initiating soy consumption or isoflavone supplementation at historic period 50 y may not take the aforementioned outcome of reducing hot flashes.
The Japanese experience
In the 1980s, Lock et al. (27) studied menopause among Japanese women and asked women virtually symptoms, including those typically experienced by American and Canadian women; they also asked the Japanese women (and their physicians) how they would describe this time of life and the symptoms they experienced. The respondents used a combination of 3 terms (sudden feeling of heat; feeling hot or flushed; blitz of claret to the head) to cover what Western women and physicians mean by the unmarried term hot flash. The Japanese women reported fewer hot flashes than their Western counterparts. The researchers concluded that fewer Japanese women were experiencing hot flashes and nighttime sweats.
Twenty years after, Melby (28) conducted a follow-up study in Nihon, this time focusing on the more linguistically nuanced terminologies as she came to sympathise how Japanese women spoke near their sensations of heat and sweating during the menopausal years. Melby included Lock's symptom list in her questionnaire only asked about hot flash terms separately, and institute there was an increase in symptom reporting in the time since Lock's report. In that location was an increase in those reporting each of the symptoms comprising the nuanced components hot flashes (Table 1) (28). Some of the caption for increased symptom reporting may involve the globalization of the Western approach to and discussion of menopause. Zeserson (29) commented on the media'southward impact on how women discuss and view their symptoms. In the case of hot flashes, Zeserson (29) noted that Japanese women began using the Americanized expression 'hotto furasshu' and became conversant with the Western terminology of "hot flash," having heard this in the media. As described earlier, at that place are a number of measurable physiological changes that establish a hot flash.
TABLE one
Symptoms recalled in previous 2-wk menstruum in Japanese women: comparison across twenty y 1
| Romanized Japanese symptom | English symptom | Lock, n = 1141 | Melby, north = 140 | Incidence |
|---|---|---|---|---|
| % | ||||
| Katakori | Shoulder stiffness | 51.seven | 62.1 | 20 |
| Zutsuu | Headache | 27.7 | 39.3 | 42 |
| Youtsuu | Lumbago | 22.4 | 35.0 | 56 |
| Benpi | Constipation | 21.1 | 25.0 | 18 |
| Hieshou | Chilliness | xvi.3 | 29.3 | fourscore |
| Iraira | Irritability | 11.ix | 28.six | 140 |
| Fumin | Insomnia | 11.iv | eleven.4 | 0 |
| Kansetsutsuu | Aches and pains in the joints | 10.9 | 15.0 | 38 |
| Kaze o yoku hiku | Frequent colds | x.four | 15.0 | 44 |
| Kyuu na nekkan nobose, hoteri | Any hot wink | 9.5 | 22.1 | 133 |
| Ki ga meiru | Depression | seven.ix | 22.9 | 190 |
| Memai | Dizziness | 7.two | ten.7 | 49 |
| Kyuu na hakkan | Sudden perspiration | four.two | 8.6 | 105 |
| Ne ase | Night sweats | 3.2 | six.4 | 100 |
| Romanized Japanese symptom | English language symptom | Lock, north = 1141 | Melby, n = 140 | Incidence |
|---|---|---|---|---|
| % | ||||
| Katakori | Shoulder stiffness | 51.7 | 62.1 | 20 |
| Zutsuu | Headache | 27.7 | 39.3 | 42 |
| Youtsuu | Lumbago | 22.4 | 35.0 | 56 |
| Benpi | Constipation | 21.1 | 25.0 | 18 |
| Hieshou | Chilliness | 16.3 | 29.3 | 80 |
| Iraira | Irritability | 11.9 | 28.6 | 140 |
| Fumin | Insomnia | xi.4 | 11.4 | 0 |
| Kansetsutsuu | Aches and pains in the joints | x.9 | 15.0 | 38 |
| Kaze o yoku hiku | Frequent colds | 10.4 | 15.0 | 44 |
| Kyuu na nekkan nobose, hoteri | Any hot flash | 9.5 | 22.i | 133 |
| Ki ga meiru | Depression | seven.9 | 22.ix | 190 |
| Memai | Dizziness | 7.two | 10.7 | 49 |
| Kyuu na hakkan | Sudden perspiration | four.two | 8.half dozen | 105 |
| Ne ase | Night sweats | three.2 | 6.4 | 100 |
1 Adapted from Melby 2005 (28) and Lock et al. (27). Reprinted by permission of Elsevier.
Table 1
Symptoms recalled in previous 2-wk period in Japanese women: comparing beyond twenty y 1
| Romanized Japanese symptom | English symptom | Lock, n = 1141 | Melby, n = 140 | Incidence |
|---|---|---|---|---|
| % | ||||
| Katakori | Shoulder stiffness | 51.7 | 62.1 | twenty |
| Zutsuu | Headache | 27.seven | 39.3 | 42 |
| Youtsuu | Lumbago | 22.iv | 35.0 | 56 |
| Benpi | Constipation | 21.1 | 25.0 | 18 |
| Hieshou | Chilliness | xvi.3 | 29.iii | 80 |
| Iraira | Irritability | xi.9 | 28.half-dozen | 140 |
| Fumin | Insomnia | eleven.4 | 11.4 | 0 |
| Kansetsutsuu | Aches and pains in the joints | 10.9 | 15.0 | 38 |
| Kaze o yoku hiku | Frequent colds | 10.4 | fifteen.0 | 44 |
| Kyuu na nekkan nobose, hoteri | Whatsoever hot wink | 9.v | 22.ane | 133 |
| Ki ga meiru | Low | 7.ix | 22.ix | 190 |
| Memai | Dizziness | 7.2 | ten.vii | 49 |
| Kyuu na hakkan | Sudden perspiration | iv.ii | eight.half-dozen | 105 |
| Ne ase | Dark sweats | 3.two | half-dozen.4 | 100 |
| Romanized Japanese symptom | English symptom | Lock, n = 1141 | Melby, north = 140 | Incidence |
|---|---|---|---|---|
| % | ||||
| Katakori | Shoulder stiffness | 51.7 | 62.1 | 20 |
| Zutsuu | Headache | 27.seven | 39.iii | 42 |
| Youtsuu | Lumbago | 22.4 | 35.0 | 56 |
| Benpi | Constipation | 21.1 | 25.0 | eighteen |
| Hieshou | Chilliness | xvi.iii | 29.3 | fourscore |
| Iraira | Irritability | 11.9 | 28.6 | 140 |
| Fumin | Insomnia | 11.4 | xi.4 | 0 |
| Kansetsutsuu | Aches and pains in the joints | ten.9 | 15.0 | 38 |
| Kaze o yoku hiku | Frequent colds | 10.4 | 15.0 | 44 |
| Kyuu na nekkan nobose, hoteri | Any hot flash | nine.v | 22.1 | 133 |
| Ki ga meiru | Depression | seven.nine | 22.nine | 190 |
| Memai | Dizziness | vii.ii | 10.7 | 49 |
| Kyuu na hakkan | Sudden perspiration | 4.two | eight.6 | 105 |
| Ne ase | Night sweats | 3.2 | half dozen.4 | 100 |
1 Adjusted from Melby 2005 (28) and Lock et al. (27). Reprinted past permission of Elsevier.
Some women'southward centre charge per unit increases, some women sweat, while others flush and feel a sensation of oestrus. In Western countries, women draw whether they affluent or sweat during a hot flash; they proper name this constellation of changes as a "hot flash" or "hot flush." Japanese women describe an individual component of hot flash awareness if they feel it. In Traditional Chinese medicine (and its Kampo counterpart in Japan), a practitioner would identify the detail characteristics of an individual woman presenting with the Western diagnosis of hot flashes, whether she sweats (sweat effusion or fa han has many unlike presentations), flushes (mian jia chao hong, eastward.chiliad., characterizes a visible malar affluent while fa re represents a generalized awareness of oestrus), or has rapid heart rate (jing ji or palpitations) [(30); K.V. Ergil, personal advice], and the diagnostic process would pb to treatment related to that blueprint of symptom presentation. Thus, non all women with a Western diagnosis of menopausal hot flashes would receive the same suggested treatment. Western investigators, too, tin apply these distinctions and stratify clinical trials to explore whether some treatments are more advisable for certain subsets of women with specific patterns of symptoms.
Interestingly, Melby (31) administered to both men and women in Nippon the same symptom questionnaire. Both groups reported shoulder stiffness (the most prevalent symptom reported by women) and men reported more night sweats than did the women (Tabular array 2) (31). How do nosotros decide which symptoms are influenced by cultural factors and expectations and which are a role of hormonal or other physiological change?
Table 2
Two-calendar week symptom prevalence in Japanese women and men ane
| Romanized Japanese symptom | English symptom | Females, due north = 32 | Males, n = 22 | χ 22 | |
|---|---|---|---|---|---|
| % | |||||
| Katakori | Shoulder stiffness | 43.8 | 40.9 | ||
| Sutoresu | Stress | 12.5 | 36.4 | 4.296 3 | |
| Kyuu na hakkan | Sudden perspiration | 12.5 | 0.0 | 2.970 4 | |
| Iraira | Irritability | 6.3 | 27.3 | 4.566 3 | |
| Ne ase | Nighttime sweats | 6.iii | 13.six | ||
| Shinkei no shinchou | Nervous tension | 0.0 | 13.6 | 4.620 iii | |
| Kentaikan | Burnout | 0.0 | 9.1 | three.021 iv | |
| Romanized Japanese symptom | English symptom | Females, due north = 32 | Males, northward = 22 | χ 22 | |
|---|---|---|---|---|---|
| % | |||||
| Katakori | Shoulder stiffness | 43.8 | forty.nine | ||
| Sutoresu | Stress | 12.5 | 36.iv | 4.296 three | |
| Kyuu na hakkan | Sudden perspiration | 12.five | 0.0 | ii.970 4 | |
| Iraira | Irritability | 6.3 | 27.3 | 4.566 3 | |
| Ne ase | Night sweats | six.3 | 13.6 | ||
| Shinkei no shinchou | Nervous tension | 0.0 | xiii.6 | 4.620 3 | |
| Kentaikan | Burnout | 0.0 | 9.ane | 3.021 4 | |
2 The nonparametric chi-square test was used to assess sexual practice divergence in symptoms experienced in the previous 2 wk and reported by >ix% of the sample.
three Significant at the 0.05 level (2-tailed).
4 Significant at the 0.x level (2-tailed).
TABLE ii
Ii-week symptom prevalence in Japanese women and men 1
| Romanized Japanese symptom | English symptom | Females, due north = 32 | Males, north = 22 | χ 22 | |
|---|---|---|---|---|---|
| % | |||||
| Katakori | Shoulder stiffness | 43.8 | 40.ix | ||
| Sutoresu | Stress | 12.five | 36.iv | iv.296 3 | |
| Kyuu na hakkan | Sudden perspiration | 12.v | 0.0 | 2.970 iv | |
| Iraira | Irritability | half dozen.iii | 27.3 | four.566 3 | |
| Ne ase | Night sweats | 6.3 | thirteen.6 | ||
| Shinkei no shinchou | Nervous tension | 0.0 | thirteen.6 | 4.620 iii | |
| Kentaikan | Exhaustion | 0.0 | nine.ane | 3.021 4 | |
| Romanized Japanese symptom | English symptom | Females, n = 32 | Males, north = 22 | χ 22 | |
|---|---|---|---|---|---|
| % | |||||
| Katakori | Shoulder stiffness | 43.viii | twoscore.nine | ||
| Sutoresu | Stress | 12.5 | 36.4 | 4.296 3 | |
| Kyuu na hakkan | Sudden perspiration | 12.5 | 0.0 | ii.970 iv | |
| Iraira | Irritability | half-dozen.3 | 27.3 | 4.566 3 | |
| Ne ase | Nighttime sweats | six.three | 13.6 | ||
| Shinkei no shinchou | Nervous tension | 0.0 | 13.6 | 4.620 3 | |
| Kentaikan | Burnout | 0.0 | 9.1 | iii.021 4 | |
ii The nonparametric chi-square exam was used to assess sex difference in symptoms experienced in the previous ii wk and reported by >nine% of the sample.
3 Meaning at the 0.05 level (two-tailed).
4 Significant at the 0.10 level (2-tailed).
Do women of Japanese ancestry really have fewer hot flashes than western women or do they just not report them?
Theories have been offered to explain the differences in hot flash prevalence around the world, including genetics, physiology, expectation, lifestyle (soy foods, exercise), or other environmental factors. Brown et al. (32) looked elsewhere to examine whether part of the explanation for fewer hot flashes among Japanese-American women might involve a lack of reporting rather than a lack of occurrence of hot flashes. Their study, conducted in Hawaii, compared objectively measured hot flashes (using the measure out of skin conductance) with self-report in women of Japanese descent and European descent living in Hilo, Hawaii. They administered a postal questionnaire asking about symptoms experienced in the by two wk and followed that with 24-h objective monitoring with diary reporting in a subset of women. The postal survey indicated that Japanese women had fewer symptoms such as backache, hot flashes, nighttime sweats, depression, and trouble sleeping (Fig. 3). Even so, the ambulatory monitor revealed no difference betwixt the groups in the percentage of women exhibiting objective hot flashes (Fig. 4). There was a singled-out difference between what was reported in the postal questionnaires and the ambulatory monitoring. Japanese-American women were significantly less likely to written report hot flashes in the previous 2 wk, yet, they had the same frequency of considerately recorded hot flashes as the European-Americans. The authors concluded that fewer reported hot flashes in women of Japanese ancestry might exist a result of reporting bias likely due to cultural perceptions of what is acceptable to hash out and study. The report of Brown et al. (33) highlights the value of objectively measuring hot flashes. There can be cultural differences in how and whether one reports hot flashes; diary use ofttimes underreports hot flashes such as those that occur during sleep or during a busy period when a hot flash is not noticed or goes unreported.
Figure 3
Symptoms reported for previous 2 wk by Japanese- and European-American Women in Hawaii surveyed by postal questionnaire. Adjusted from Brown et al. (32) with permission from Wolters Kluwer.
FIGURE iii
Symptoms reported for previous two wk by Japanese- and European-American Women in Hawaii surveyed by postal questionnaire. Adapted from Brown et al. (32) with permission from Wolters Kluwer.
FIGURE 4
Incidence and mean number of hot flashes among Japanese- and European-American women wearing a hot wink monitor. Adapted from Dark-brown et al. (32) with permission from Wolters Kluwer.
FIGURE four
Incidence and mean number of hot flashes amidst Japanese- and European-American women wearing a hot flash monitor. Adapted from Dark-brown et al. (32) with permission from Wolters Kluwer.
Clinical inquiry has been hampered by the lack of a hot wink monitor that is authentic and easy-to-utilise in convalescent subjects. Most of the portable monitors available for measuring peel conductance (or other physiological signals) are cumbersome to wearable and take wires that practise non facilitate ease of use. A new, miniature, wireless monitor, developed past Bahr Direction in collaboration with researchers at the University of California, San Francisco, promises increased accuracy and ease of utilise (34,35).
Emerging areas of interest
Brain imaging techniques such as functional MRI are being used to examine brain role during hot flashes. Initial studies of brain activation during hot flashes have establish that the insula and anterior cingulated cortex are activated during hot flashes (36). Better understanding of the neural control of hot flashes will provide further insight into mechanisms.
Another area of growing interest is the human relationship between hot flashes and polymorphisms of genes involved in estrogen function, such as sex steroid metabolizing enzymes and estrogen receptors. Given that estrogen plays some role in the hot flash miracle, investigators are examining variation in genes coding for enzymes involved in estrogen synthesis and hormone interconversion for a possible role in the variance in observed circulating hormone levels (37). Genetic polymorphisms are also existence studied in an endeavour to explicate observations of race/ethnic differences in hot flash prevalences (38), such equally seen in the Study of Women Across the Nation in the US. Two studies indicate that there are certain race/ethnicity associations between polymorphisms for sex metabolizing hormones (39,40). This line of inquiry is in its infancy but may provide new insights into the often conflicting and variable results of studies examining factors that might predict who almost is at adventure for hot flashes.
The written report of equol for the handling of hot flashes holds promise and clinical and basic science studies are underway in the US, Japan, and elsewhere. To better study soy, equol, or any herbal or pharmaceutical amanuensis for the treatment of hot flashes, researchers need better measurement techniques, including better questionnaires that ask questions in a culturally sensitive context. More inquiry on the basic underlying physiology and brain office during hot flashes is needed to meliorate understand mechanisms that can lead to the design of treatments targeting these mechanisms.
Summary
Hot flashes remain a specially bothersome problem for a majority of menopausal women in the US and elsewhere and a principal reason for which women in the menopausal years seek treatment. Nonetheless, afterwards >xl y of studying hot flash physiology, we still do non understand the etiology, nor practice nosotros sympathize how the almost effective treatment to engagement, estrogen, works to reduce hot flashes. There has been substantial exam of and insight into cross-cultural differences, the nuances of linguistic expressions, and dietary and other factors that are providing means of stratifying results to meliorate understand the variability in responses. Newer research is focusing on brain function and genetic polymorphisms, both of which add new levels of complexity to what is obviously a very rich and compelling expanse for investigation. After so many years with insufficient research attention, the time and measurement tools are at present ready for a more than sophisticated examination of hot flashes. Whatever boosted understanding of mechanism would provide valuable guidance for those wishing to written report and develop new treatments for this age-old trouble.
Thanks to Kevin V. Ergil, Associate Professor, Finger Lakes School of Acupuncture and Oriental Medicine at New York Chiropractic College, for personal advice almost traditional Chinese medicine. The sole author had responsibility for all parts of the manuscript.
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Footnotes
i Published in a supplement to The Journal of Nutrition. Presented at the "Equol, Soy, and Menopause Research Leadership Conference" held in Washington, DC, June xvi, 2009. The supplement coordinator for this supplement is Kara Lewis, Life Sciences Research Organisation (LSRO) Senior Staff Scientist. The supplement is the responsibility of the guest editors to whom the Editor of The Periodical of Nutrition has delegated supervision of both technical conformity to the published regulations of The Journal of Diet and general oversight of the scientific merit of each article. Publication costs for this supplement were defrayed in part by the payment of page charges. This publication must therefore exist hereby marked "advertizement" in accordance with 18 USC section 1734 solely to point this fact. The Guest Editor for this supplement is Neil Shay. Invitee Editor disclosure: Neil Shay declares no conflict of interest. Supplement Coordinator disclosure: Kara Lewis is currently under contract with and receives bounty from the supplement sponsor. She was also compensated for attending and organizing the Equol, Soy, and Menopause Research Leadership Conference and for organizing, writing, editing, or reviewing, and collection of supplemental manuscripts. The opinions expressed in this publication are those of the authors and are non attributable to the sponsors or the publisher, Editor, or Editorial Board of The Journal of Nutrition.
© 2010 The American Establish of Nutrition
Source: https://academic.oup.com/jn/article/140/7/1380S/4689019
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