The most common cause of homocystinuria is a deficiency in the enzyme cystathionine -synthase. Approximately 50 percent of untreated individuals die before age 25. Congenital hypothyroidism . This disorder is caused by inadequate production of thyroxine, a thyroid hormone. Symptoms include mental retardation, growth failure, deafness, neurologic abnormalities, and slow metabolism.
Treatment is levothyroxine, thyroid hormone replacement therapy, given orally.
Biotinidase deficiency . A deficiency of biotin, part of the Vitamin B complex, leading to multiple carboxylase deficiency. Symptoms include seizures, hypotonia, immune system impairment, skin rashes, hair loss, hearing loss, and mental retardation. Treatment is oral biotin supplementation. CAH causes increased androgen production, resulting in ambiguous genitalia and virilization in girls and early virilization in boys.