One study showed that nausea and vomiting, which often occur during the first trimester of pregnancy, are mainly caused by a hormone, and this finding may help to better ** morning sickness, including rare, life-threatening morning sickness.
This study confirms previous studies that all point to the hormone called GDF15. Researchers have found that the amount of hormones a woman circulates in her bloodstream during pregnancy, as well as the amount of hormone she was exposed to before pregnancy, affects the severity of her symptoms.
More than two-thirds of pregnant women experience nausea and vomiting during the first trimester of pregnancy. About 2% of pregnant women are hospitalized with hyperemesis gravidarum**, a condition that causes persistent vomiting and nausea throughout pregnancy, leading to malnutrition, weight loss and dehydration, as well as increasing the risk of preterm birth, preeclampsia and blood clots, threatening the life of both mother and fetus.
Perhaps because nausea and vomiting are so common during pregnancy, doctors often ignore morning sickness as a psychological problem, even though it's the main cause of hospitalization in the first trimester, experts say.
Dr. Marlena Fezzo, a geneticist at the University of Southern California's Keck School of Medicine and co-author of the new study, said:"I've been working on this for 20 years, but there are still reports of women dying and women being treated as a result. "
She knows firsthand the pain of the disease. In 1999, during her second pregnancy, she was unable to eat or drink without vomiting, lost weight rapidly, became weak, and could not stand or walk. But the doctor was dismissive of it, believing that she was exaggerating her symptoms to get attention.
She was eventually hospitalized and had a miscarriage at 15 weeks.
Dr. Fezzo said she had asked the National Institutes of Health to fund a genetic study on hyperemesis, but was denied. But undeterred, she convinced 23andme, a popular genetic testing company, to include questions about morning sickness in a survey of tens of thousands of customers. In 2018, she published an article showing that clients with morning sickness often carry variants of the GDF15 gene.
Hormones are chemicals that carry messages in the body. Many tissues release GDF15 in response to stress, such as infection, and the signal is highly specific: receptors for this hormone gather in the brain where they are responsible for feeling unwell and vomiting.
In the new study, Dr. Fezzo and collaborators from the University of Cambridge in the United Kingdom measured the hormone in the blood of pregnant women and analyzed genetic risk factors for morning sickness.
The investigators found that GDF15 levels during pregnancy were significantly higher in women with morning sickness than in asymptomatic women. But the effects of this hormone appear to depend on the woman's sensitivity and exposure to this hormone before pregnancy.
For example, researchers have found that some women in Sri Lanka suffer from a rare blood disorder that causes chronically high levels of GDF15, but they rarely experience nausea or vomiting during pregnancy.
Dr. Stephen Olahili, an endocrinologist at the University of Cambridge who led the study, said:"This completely eliminates all nausea symptoms. They have almost zero pregnancy symptoms. "
Dr. Olaheli speculates that long-term exposure to GDF15 before pregnancy may have a protective effect, making women less sensitive to hormonal surges caused by fetal development.
In laboratory experiments, scientists exposed some mice to small amounts of the hormone. After three days, when the mice ingested a larger dose of the hormone, their appetite did not decrease as much as the mice that did not consume the earlier dose, suggesting a strong desensitization effect.
Experts say the findings offer hope for the better. If clinical trials find that the drug is safe during pregnancy, people with morning sickness may one day be able to take the drug to block the hormone's action in the brain. Trials are currently underway in cancer patients who are also suffering from loss of appetite and vomiting caused by GDF15 to test the efficacy of such drugs.
It is even possible to prevent this from happening. Women at risk, such as those who experienced severe nausea and vomiting during a previous pregnancy, can take low doses of this hormone before pregnancy (a diabetes drug metformin, which increases levels of GDF15, has been used to help some patients have children).
Dr Rachel Frittshi, a geneticist at the University of Exeter, who was not involved in the study, said the new study is interesting because it demonstrates a causal relationship between GDF15 and the disease from a genetic perspective and will help the disease gain more recognition.
Dr. Frittesch said:"Many people have the assumption that women should be able to cope with this situation, and with this biological explanation, people will be more convinced that this is a real phenomenon and not a thought in someone's head"。