Hypothyroidism rarely causes diarrhea; it is caused by a lack of thyroid hormones in the blood. Thyroid hormone can participate in the process of material metabolism and energy metabolism, and can promote intestinal peristalsis. Therefore, when there is a deficiency of thyroid hormone, patients will experience slower intestinal peristalsis, loss of appetite, bloating, constipation, etc. Severe hypothyroidism can also manifest as intestinal paralysis and so on. Therefore, untreated hypothyroidism patients will not develop diarrhea. If diarrhea occurs in patients with hypothyroidism, the following situations should be considered: First, the combination of other diseases that cause diarrhea, such as various acute and chronic enteritis. Second, the treatment of hypothyroidism drugs to take too large a dose of drugs lead to drug hyperthyroidism, there will also be an increase in the number of stools. Therefore, if patients with hypothyroidism have diarrhea symptoms, they should further check their thyroid function and adjust the dosage of medication for hypothyroidism.