Pregnancy, the trigger for nausea identified

The attacks of nausea related to pregnancyparticularly during the first few weeks, may now have a scientifically based reason. According to a study signed by a group of researchers from the University of Pennsylvania together with British and Sri Lankan colleagues published on Nature it all depends on a hormone secreted by developing fetuses: women are more sensitive to the hormone GDF15which increases in the early stages of gestation, can experience deeper and debilitating nausea which also includes episodes of vomiting until it evolves into a real pathology, the hyperemesis gravidarum. If, in fact, nausea and vomiting are a common presence during pregnancy (they affect approximately 70% of women at various times), on certain occasions – between 0.2 and 2% of cases – this condition can lead to weight loss, dehydration and even hospitalization.

«For the first time, hyperemesis gravidarum could be addressed at the rootrather than simply alleviating the symptoms” he explains Tito Borner, physiologist at the University of Pennsylvania. The discovery could therefore open up avenues for a hypothetical preventive treatment: “Now we have a clear vision of what can cause this problem and a path for both treatment and prevention” he added Stephen O’Rahillyco-author of the study, a metabolism researcher at the University of Cambridge, UK.

According to the investigation, women who show lower levels of GDF15 before pregnancy experience more severe symptoms once pregnant. Marlena Fejzo, one of the authors, explains that “we now know that women feel unwell during pregnancy when they are exposed to higher levels of the hormone GDF15 than they are used to.” This essentially means that administering GDF15 to subjects at high risk of hyperemesis gravidarum before pregnancy could protect future mothers from stronger nausea and precisely from hyperemesis gravidarum.

The study – following some 2018 research that had feared similar links – demonstrated that GDF15, produced at low levels by organs including the prostate, bladder and kidneys, can trigger nausea by binding to specialized receptors in the brainstem. After ingesting toxic substances and at the beginning of pregnancy, levels of this hormone increase, causing nausea and other debilitating symptoms. “It’s usually worse in the first trimester and then gradually fades,” O’Rahilly says.

From the point of view evolutionary this hormone may have developed to protect people from poisoning and, in cascade, for protect the developing fetus from toxic substances. Specifically, O’Rahilly and his colleagues found that GDF15 levels in the blood were substantially higher in nearly 60 pregnant women who had experienced nausea and vomiting compared with about 60 women who had experienced few or no complaints. The researchers then compared the levels of different variants of GDF15 produced by placental cells derived from mothers and fetuses and found that it was the fetal cells that produced most of the hormone.

The team also discovered – through experiments on mice – that people with some genetic variants of GDF15, which had previously been linked to a higher risk of developing hyperemesis gravidarum, actually recorded lower GDF15 levels. By analyzing the genetic data of over 18 thousand people, researchers discovered that higher levels of this hormone in non-pregnant people could have reduced the risk of developing hyperemesis gravidarum if they had become pregnant. And they also probed the presence or absence of nausea in women affected by Mediterranean anemiaa very serious hereditary blood disease which among other characteristics involves high levels of GDF15: only 5% he admitted to having tried them. This suggests, as previously mentioned, that women react less to the hormone during pregnancy if they previously had higher levels of GDF15. Several more studies will be needed to understand any side effects for preventive treatments based on the hormone, given that we still need to understand its role during pregnancy.

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