What is the primary hormonal cause of heartburn in pregnant patients?

The primary hormonal cause of heartburn in pregnant patients is related to the effects of progesterone. As pregnancy progresses, levels of progesterone increase significantly, and this hormone has a relaxing effect on smooth muscle, including the lower esophageal sphincter (LES). The LES is crucial for preventing gastric contents from refluxing into the esophagus. When progesterone relaxes this sphincter, it becomes less effective at preventing reflux, which can lead to heartburn and gastroesophageal reflux disease (GERD) symptoms commonly experienced during pregnancy.

This relationship explains why many pregnant individuals experience heartburn as their pregnancies progress, especially in the third trimester when progesterone levels are particularly high, increasing the likelihood of sphincter relaxation and subsequent reflux.

The other options do not accurately reflect the hormonal influences relevant to heartburn in pregnancy. Estrogen and testosterone have different roles in the body and do not primarily facilitate sphincter relaxation in the context of heartburn, while the assertion that progesterone increases gastric secretions is misleading. The heartburn is primarily a result of the relaxation of the LES rather than an increase in gastric secretions directly leading to reflux.