GDF15 (growth differentiation factor 15) is a protein hormone that acts as a stress signal in the body, suppressing appetite and influencing energy balance. It belongs to the TGF-beta superfamily of proteins and is produced by nearly every tissue, with levels rising sharply whenever cells are under strain from disease, injury, or even intense exercise. In recent years, GDF15 has drawn enormous attention as a biomarker for heart disease, cancer, and pregnancy-related nausea, and as a potential drug target for obesity.
How GDF15 Works in the Body
GDF15 circulates in the blood and delivers its signal to a very specific part of the brain. Its receptor, called GFRAL, exists only in a small region of the hindbrain known as the area postrema and a neighboring structure called the nucleus of the solitary tract. These areas sit outside the blood-brain barrier and serve as the brain’s chemosensory outpost, detecting toxins and triggering nausea. When GDF15 binds to GFRAL, it activates a co-receptor called RET, which sets off a chain of signals that ultimately reduce appetite and increase feelings of sickness or fullness.
This narrow location in the brain is key to understanding why GDF15 causes such a specific response. Rather than broadly altering metabolism, it works through the same neural circuitry that makes you feel nauseated. That connection explains its role in conditions ranging from morning sickness to the severe weight loss seen in advanced cancer.
Normal Blood Levels and What Raises Them
In a large study of over 18,500 adults without heart disease or stroke, the overall median GDF15 level was about 808 pg/mL. Levels climb steadily with age. Men under 30 had a median of 537 pg/mL, while men over 80 averaged 2,152 pg/mL. Women followed a similar pattern, starting at 628 pg/mL in those under 30 and reaching 1,847 pg/mL after age 80. Sex differences were modest at most ages.
A wide range of stressors push GDF15 higher. People with a history of heart disease or stroke had a median level of about 1,306 pg/mL, while those with heart failure averaged 1,776 pg/mL. The most dramatic elevation occurs during pregnancy, when median levels reached 19,311 pg/mL, roughly 24 times the normal baseline. Even a single bout of hard exercise raises GDF15 by about 34% immediately afterward, with levels continuing to climb to 64% above resting values during the two hours of recovery. Interestingly, this exercise-related spike does not appear to come from skeletal muscle itself, suggesting other tissues release GDF15 in response to the metabolic demand.
GDF15 and Pregnancy Nausea
One of the most striking recent discoveries about GDF15 is its role in morning sickness. A 2023 study published in Nature confirmed that higher GDF15 levels in maternal blood are associated with more severe nausea and vomiting during pregnancy. Women who reported vomiting had significantly higher levels than those with no nausea at all.
The GDF15 driving pregnancy nausea comes largely from the fetus and placenta, not the mother. A woman’s sensitivity to the hormone appears to depend partly on how much GDF15 she was exposed to before becoming pregnant. Those with naturally low baseline levels may be less accustomed to the hormone, making them more reactive to the enormous surge that occurs once a pregnancy begins. This framework helps explain why hyperemesis gravidarum, the most severe form of pregnancy sickness, affects some women and not others despite similar hormone levels.
Connection to Metformin and Weight
Metformin, the most widely prescribed diabetes medication in the world, turns out to work partly through GDF15. Two independent randomized controlled trials showed that metformin increases circulating GDF15, with the hormone rising primarily from the intestine and kidneys. In mice fed a high-fat diet, metformin prevented weight gain in normal animals but failed to do so in mice that lacked either GDF15 or its brain receptor GFRAL. When researchers gave obese mice an antibody that blocked GFRAL, metformin’s weight-lowering effect reversed.
Among people taking metformin, the change in GDF15 levels correlated directly with weight loss. Those whose GDF15 rose more tended to lose more weight over 18 months. Notably, metformin still lowered blood sugar even when GDF15 signaling was blocked, meaning its glucose-lowering and weight-lowering effects operate through separate pathways.
Role in Cancer and Muscle Wasting
Many cancers produce large amounts of GDF15, and this overproduction is now recognized as a major driver of cancer cachexia, the devastating syndrome of appetite loss and muscle wasting that affects up to 80% of people with advanced cancer. GDF15 suppresses appetite through its action on GFRAL in the hindbrain, but it also activates the body’s stress hormone axis, triggering the release of cortisol and related hormones. Elevated stress hormones in turn accelerate the breakdown of muscle protein.
Beyond appetite suppression, GDF15 appears to damage muscle more directly. In laboratory studies, the hormone switches on genes that tag muscle proteins for destruction while simultaneously reducing muscle fiber diameter. Animal models of colon, lung, and pancreatic cancer show that this muscle breakdown is driven both by the appetite-suppressing brain signal and by the stress hormones GDF15 triggers. This dual mechanism makes GDF15 a particularly destructive force in cancer, and blocking it has become a focus of drug development for cachexia.
GDF15 as a Heart Disease Biomarker
Cardiologists have studied GDF15 extensively as a prognostic marker. In patients admitted with acute coronary syndromes (heart attacks and unstable angina), roughly two-thirds had GDF15 levels above 1,200 pg/mL, the upper limit of normal in healthy people. About one-third had levels above 1,800 pg/mL. A level of 1,808 pg/mL emerged as the best cutoff for predicting death within one year, with both sensitivity and specificity near 69%.
GDF15 is not used to diagnose a heart attack the way troponin is. Instead, it reflects the overall burden of stress on the cardiovascular system, including inflammation, reduced blood flow, and strain on the heart muscle. Higher levels consistently predict worse outcomes across a range of cardiac conditions, making it useful as a risk-stratification tool rather than a diagnostic one.
Is GDF15 Testing Available?
GDF15 blood tests exist but are not yet part of routine clinical practice. The U.S. FDA currently categorizes GDF15 assays under “enforcement discretion,” meaning the tests are available through specialized laboratories but have not gone through formal FDA approval for a specific diagnostic use. In practice, GDF15 testing is most commonly ordered in research settings or by cardiologists evaluating complex cases. As pharmaceutical companies develop drugs targeting the GDF15-GFRAL pathway for obesity and cachexia, clinical demand for standardized testing is likely to grow.