Monarch Disease Ontology entry MONDO_0009718 (myxedema) can be described as follows. A condition characterized by severe hypothyroidism that is caused by autoimmune thyroid gland disorders, surgical reduction of thyroid tissue, radiation exposure, and viral infections. Signs and symptoms include generalized fatigue, lethargy, increased body weight, pale, edematous and thickened skin, low blood pressure, constipation and cold intolerance.