A single hormone is responsible for nausea and vomiting during pregnancy. This was arrived at by a group of scientists from specialist institutes mainly from Great Britain and the USA, who published their discovery on Wednesday in the journal Nature.
It is a protein, the growth hormone GDF15, which physiologically occurs in low concentrations in a number of tissues and organs including the liver, kidneys, heart or lungs. “Physiologically, higher concentrations of GDF-15 occur at an older age and during pregnancy, when they are produced by the placenta,” explains Štěpán Havránek from the 1st Faculty of Medicine of the Charles University in Prague on his website.
Scientists now write in Nature that the severity of nausea during pregnancy is governed by the amount of this hormone circulating in the woman’s blood. The level of GDF15 before the actual pregnancy is also an important factor.
The discovery could lead to better treatments for morning sickness, including rare, life-threatening cases, the researchers said.
The New York Times (NYT) writes in an article dedicated to the discovery that up to two thirds of pregnant women suffer from nausea and vomiting during the first trimester. Meanwhile, roughly two percent of women are so sick that they have to be hospitalized – due to a condition called hyperemesis gravidarum.
This condition causes persistent nausea and vomiting, and the woman is unable to take in any food or liquids. This leads to dehydration and malnutrition, there is even a risk of metabolic disruption. Hyperemesis gravidarum generally threatens the life of the mother and the fetus – it increases the risk of miscarriage, blood clots or preeclampsia. (In short, it is an incorrect development of the placenta, as a result of various changes, the mother’s blood pressure increases dangerously, editor’s note)
For a long time, hyperemesis gravidarum was thought to be more psychological in origin. Global celebrities who suffered from this condition made a major contribution to public awareness. Catherine, the future British queen, wife of Prince William, will probably be the most famous in the Czech Republic. She had to be hospitalized repeatedly due to debilitating nausea.
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“I have been dealing with this issue for twenty years. And yet there are still reports of hyperemesis gravidarum women dying, of being mistreated,” said study co-author Marlena Fejzo, a geneticist at the University of Southern California Keck School of Medicine.
She described to the NYT that she knows firsthand how bad it can be for women in this condition. During her second pregnancy (in 1999), she could neither eat nor drink without vomiting. She quickly lost weight, became weak, and finally could not even stand up. She heard from the doctor that he was exaggerating, that he was trying to draw attention to himself. She ended up in the hospital, where she miscarried at 15 weeks.
In the following years, she tried to study hyperemesis, but in vain applied for the grants needed to create the study. In 2018, she first published findings that the condition could be related to GDF15 levels.
In a study published in Nature, it is written that the protein is released by many tissues in response to various stimuli, for example stress, infection: “Its signal is highly specific: Receptors for this hormone are clustered in the part of the brain that is responsible for nausea and vomiting” .
The researchers found that women with hyperemesis gravidarum had significantly higher levels of GDF15 during pregnancy than those without symptoms.
“However, the effect of the hormone appears to depend on the woman’s sensitivity and exposure to the hormone before pregnancy. For example, researchers found that women in Sri Lanka with a rare blood disorder causing chronically high levels of GDF15 rarely experienced nausea or vomiting during pregnancy,” the NYT quotes.
Stephen O’Rahilly, a Cambridge endocrinologist who led the research, believes that long-term exposure to GDF15 before pregnancy could have a protective effect. That is, after women become pregnant, they will be less sensitive to the surge of hormones caused by the developing fetus.