myxedema (mĬksədē´mə), condition associated with severe hypothyroidism and lack of thyroid hormone in the adult. In the child it is known as cretinism. Symptoms include a dry swelling of the skin, slowed speech and mental awareness, deepened voice, intolerance to cold, fatigue and weakness, and nonspecific degeneration of the heart. Most cases result from atrophy of the thyroid from unknown causes, although surgical removal or irradiation of the gland also precipitates the disorder. Myxedema is treated by administering synthetic preparations of thyroxine (thryoid hormone), liothyronine (triiiodothyronine), a combination of the two synthetic hormones, and desicated animal thyroid.