Hyperthyroidism, also known as overactive thyroid, is a condition where the thyroid gland produces and releases excessive amounts of thyroid hormones. This affects various systems throughout the body, leading to a range of hypermetabolic symptoms.

For instance, in the digestive system, it can manifest as increased intestinal motility, frequent bowel movements, or loose stools. Some patients may also experience nausea and vomiting.

Excessive thyroid hormone production can also cause liver damage, known as hyperthyroid liver injury, which is indicated by elevated levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). In such cases, digestive symptoms like nausea and vomiting become more pronounced.

Additionally, if a patient develops hyperthyroid heart disease, or even complete heart failure, the resulting systemic congestion can lead to digestive system congestion, also presenting as nausea and vomiting.