许多妇女在更年期时会经历潮热，超过四分之三的女性在更年期有潮热现象。这种突然发热的感觉会从躯体传递到脸部而令人不快。有的妇女满脸通红，也有人感到心跳加快，感觉焦虑。这样的情况可能一天出现几次，甚至每个小时都出现，因人而异。潮热来临时，人的体温并没有变化，真正升温的是皮肤。通常，潮热感会持续３０秒至５分钟。
目前科学家对于潮热为何发生尚无定论。一种理论是，在潮热过程中，雌激素含量波动和脑下垂体产生的激素导致下丘脑出现混乱。下丘脑是大脑中控制血压、血液流动和电解质平衡以及体温的区域。这一区域在保持人体有效运转时，能从人体的所有部分得到信息。如果它感觉有问题，会迅速采取行动，调整心率和经过皮肤的血流量等。
在热感到来前，下丘脑得到皮肤过热的错误信息，因此它试图让人平静下来。它会促使心跳加快，血液循环加速，皮肤中的血管扩张，以便让更多的血液流通。如此一来，人体就会散发热量，汗腺也会超速运转。满脸通红的效果就由血管扩张引起。
有三项新的研究探索基因、肥胖和酒精摄取量对于女性潮热强度和频率的影响。这些研究是由伊利诺伊大学Jodi Flaws教授及马里兰大学、巴尔的摩Mercy医疗中心和约翰霍浦金斯大学医学院的同仁所共同发表的。
医师长久以来便注意到，有些因素如抽烟，会增加女性发生潮热的强度及频率，而且非裔妇女发生严重潮热的风险也较高。
在这项包含639 名45 到54岁女性的研究中，研究人员观察编码各激素的基因之差异，以及了解肥胖和饮酒对于潮热的影响。
一项之前的研究发现潮热频率、强度和时间较长的女性，体内代谢雌性激素的酵素：细胞色素P450 1B1含量较高。而这篇新研究也发现此基因多形性与较低的雄性激素DHEA-S及孕酮含量有关。研究人员也发现肥胖与潮热有关，因为BMI值较大的女性，睪固酮含量较高，总estradiol、estrone、孕酮和性激素结合球蛋白(SHBG)的量较低。第三项研究则发现，适度饮酒(每个月三份酒类饮料)可以使潮热的严重度减少百分之25。
(资料来源 : 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
