許多婦女在更年期時(shí)會(huì)經(jīng)歷潮熱，超過(guò)四分之三的女性在更年期有潮熱現(xiàn)象,。這種突然發(fā)熱的感覺(jué)會(huì)從軀體傳遞到臉部而令人不快,。有的婦女滿(mǎn)臉通紅，也有人感到心跳加快,，感覺(jué)焦慮,。這樣的情況可能一天出現(xiàn)幾次，甚至每個(gè)小時(shí)都出現(xiàn),，因人而異,。潮熱來(lái)臨時(shí)，人的體溫并沒(méi)有變化,，真正升溫的是皮膚,。通常，潮熱感會(huì)持續(xù)３０秒至５分鐘,。
目前科學(xué)家對(duì)于潮熱為何發(fā)生尚無(wú)定論,。一種理論是，在潮熱過(guò)程中,，雌激素含量波動(dòng)和腦下垂體產(chǎn)生的激素導(dǎo)致下丘腦出現(xiàn)混亂,。下丘腦是大腦中控制血壓、血液流動(dòng)和電解質(zhì)平衡以及體溫的區(qū)域,。這一區(qū)域在保持人體有效運(yùn)轉(zhuǎn)時(shí),，能從人體的所有部分得到信息。如果它感覺(jué)有問(wèn)題,，會(huì)迅速采取行動(dòng),，調(diào)整心率和經(jīng)過(guò)皮膚的血流量等。
在熱感到來(lái)前,，下丘腦得到皮膚過(guò)熱的錯(cuò)誤信息,，因此它試圖讓人平靜下來(lái)。它會(huì)促使心跳加快，血液循環(huán)加速,，皮膚中的血管擴(kuò)張,，以便讓更多的血液流通。如此一來(lái),，人體就會(huì)散發(fā)熱量,，汗腺也會(huì)超速運(yùn)轉(zhuǎn)。滿(mǎn)臉通紅的效果就由血管擴(kuò)張引起,。
有三項(xiàng)新的研究探索基因,、肥胖和酒精攝取量對(duì)于女性潮熱強(qiáng)度和頻率的影響。這些研究是由伊利諾伊大學(xué)Jodi Flaws教授及馬里蘭大學(xué),、巴爾的摩Mercy醫(yī)療中心和約翰霍浦金斯大學(xué)醫(yī)學(xué)院的同仁所共同發(fā)表的,。
醫(yī)師長(zhǎng)久以來(lái)便注意到，有些因素如抽煙,，會(huì)增加女性發(fā)生潮熱的強(qiáng)度及頻率,，而且非裔婦女發(fā)生嚴(yán)重潮熱的風(fēng)險(xiǎn)也較高。
在這項(xiàng)包含639 名45 到54歲女性的研究中,，研究人員觀察編碼各激素的基因之差異,，以及了解肥胖和飲酒對(duì)于潮熱的影響。
一項(xiàng)之前的研究發(fā)現(xiàn)潮熱頻率,、強(qiáng)度和時(shí)間較長(zhǎng)的女性,，體內(nèi)代謝雌性激素的酵素：細(xì)胞色素P450 1B1含量較高。而這篇新研究也發(fā)現(xiàn)此基因多形性與較低的雄性激素DHEA-S及孕酮含量有關(guān),。研究人員也發(fā)現(xiàn)肥胖與潮熱有關(guān),，因?yàn)锽MI值較大的女性，睪固酮含量較高,，總estradiol,、estrone、孕酮和性激素結(jié)合球蛋白(SHBG)的量較低,。第三項(xiàng)研究則發(fā)現(xiàn),，適度飲酒(每個(gè)月三份酒類(lèi)飲料)可以使潮熱的嚴(yán)重度減少百分之25。
(資料來(lái)源 : Bio.com)
英文原文:
Hot Flashes: Studies Explore the Role of Genes, Obesity and Alcohol
04/24/07 -- Many women in the menopausal transition experience hot flashes: unpredictable, sometimes disruptive, periods of intense heat in the upper torso, neck and face. Although generations of physicians have prescribed hormones to reduce these symptoms, very little research has focused on the underlying causes of hot flashes.
Three new studies explore the role of genes, obesity and alcohol consumption in contributing to - or lessening - the intensity and frequency of hot flashes in midlife women. These studies are part of a five-year research effort led by University of Illinois veterinary biosciences professor Jodi Flaws and colleagues at the University of Maryland, Mercy Medical Center in Baltimore and the School of Medicine at Johns Hopkins University.
Physicians have long noted that some factors, such as smoking, increase the likelihood that a woman will experience more - or more intense - hot flashes than other women. Race also appears to play a role, with African American women at higher risk than others. But the mechanisms that cause some women to suffer from severe (frequent and intense) hot flashes have remained a mystery.
"Even though more than 40 million women experience hot flashes each year," the authors wrote in their paper published in Maturitas, "little is known about the factors that predispose women to hot flashes."
To examine whether genetics might play a role in hot flashes, Flaws and her colleagues conducted a cross-sectional study involving 639 women aged 45 to 54. The researchers looked at individual differences in the genes that code for various hormones. An earlier study by the same team had found that one of these genetic polymorphisms, in an estrogen metabolizing enzyme, cytochrome P450 1B1, was more common in women who reported higher-than-average frequency, intensity and duration of hot flashes.
The new study tied the same genetic polymorphism to lower levels of an androgen known as DHEA-S, and to lower progesterone levels.
These are the first studies to find evidence of a genetic basis for hot flashes, and the first to look at genetic polymorphisms associated with hormone levels in healthy women with and without hot flashes.
The progesterone finding is of particular interest, said Flaws, because the medical community has focused almost exclusively on the role of low estrogen levels in bringing on hot flashes. Hormone replacement therapy, which is sometimes offered to women to alleviate hot flashes or other symptoms of the menopausal transition, may include one or more estrogens alone or in combination with progesterone or an analogue, progestin.
"We think there should be more studies looking at the role of progesterone in causing hot flashes," Flaws said.
The research team identified a second polymorphism, in a gene encoding an enzyme, 3-beta-hydroxysteroid dehydrogenase, which also is associated with an increase in hot flashes.
"People typically didn?t think of hot flashes as having a genetic component," Flaws said. "Now we have some evidence that there is at least in part some genetics behind it."
In another paper, published in the journal Climacteric, the researchers used the same data to analyze the link between obesity and hot flashes. They had shown in an earlier study that obesity is associated with more frequent and intense hot flashes in midlife women. They now wanted to see what might be causing this effect: Did the higher incidence of hot flashes in obese women correlate with varying levels of specific hormones or other factors?
When looking at blood levels of specific hormones and related enzymes, the researchers found a significant link between obesity and hormone levels. Higher body mass index (BMI) was significantly correlated with higher testosterone and lower total estradiol, estrone, progesterone and sex hormone binding globulin (SHBG) in midlife women.
The researchers were surprised by the findings related to estrogen, because adipose tissue produces and stores estradiol, the major estrogen in humans. Most people had assumed that obese women would have higher circulating estrogen levels because of this, Flaws said. That assumption turned out to be incorrect, at least for women in midlife.
"It could be that estrogen levels are higher in the fat, but not circulating in the blood," she said. "It's the blood that gets to the brain and to the thermoregulatory centers that govern hot flashes."
A third analysis, published in the journal Fertility and Sterility, examined the influence of alcohol consumption on hot flashes in midlife women.
This study attempted to explain an earlier finding that moderate alcohol consumption (up to three drinks per month) actually reduced the severity of hot flashes by 25 percent. This effect vanished in women who consumed more than three drinks per month.
Because alcohol consumption is known to affect metabolism in some animals, the team thought that light drinking might alter sex steroid hormone levels in midlife women. But their analysis failed to turn up any significant hormonal differences between the alcohol users and the women who never used alcohol.
"We don?t know why (moderate alcohol consumption) is reducing the risk of hot flashes, other than it doesn't seem to be doing so by changing hormone levels," Flaws said.
Together, these studies point to some risk factors for hot flashes that women can change and others that cannot be changed, Flaws said.
"Body mass index, alcohol use and smoking are three things that can change," she said. "So probably if women quit smoking, and they lose weight, it will reduce their risk. If they (engage in) light drinking, that might also reduce the risk of hot flashes. And then there's the genetic piece, which we can't change."
Source: University of Illinois at Urbana-Champaign
