A case of primary congenital hipothyroidism, with acentuated symptoms of myxdema together with great psychic and physical deficiency, is referred to. The out standing clinical findings were an increase in pubic hair and sings to right ventricular hypertrophy, whose pathogeny is commented. The clinical evolution after three years of treatment, and the necessity of begining treatment as early as possible so as to obtain greater efficiency in the recuperation of psychic deficency, is also referred to.