What hormone causes an upset stomach?
Short answer: Progesterone is a common hormone that causes an upset stomach, particularly during pregnancy and the luteal phase of the menstrual cycle. Other hormones such as gastrin and serotonin (in the gut) can also provoke acid-related discomfort, nausea, or altered motility.
Explanation
Progesterone relaxes smooth muscle throughout the body, including gastrointestinal (GI) smooth muscle and the lower esophageal sphincter. That relaxation slows gastric emptying and intestinal transit, and can promote bloating, constipation, reflux and nausea. Gastrin is a hormone that increases stomach acid production and can contribute to heartburn or dyspepsia. Enteric serotonin (5-HT) modulates GI motility and communicates with vagal pathways; excess serotonin signaling (or activation of 5-HT3 receptors) is a well-established cause of nausea and vomiting. Cholecystokinin and other gut peptides can cause cramping or discomfort in some contexts, but progesterone, gastrin and serotonin are the most commonly implicated hormonal contributors to an “upset stomach.”
Tips
- Eat smaller, more frequent meals to reduce reflux and bloating.
- Avoid high-fat, very spicy, and carbonated foods that delay gastric emptying or increase acid.
- Try ginger or peppermint for mild nausea (unless contraindicated in pregnancy or reflux).
- Elevate the head of the bed and avoid lying down soon after eating to reduce reflux.
- See a healthcare provider if symptoms are severe, persistent, or occur with pregnancy—treatment or testing for hormonal causes may be needed.
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