Congenital hypothyroidism and the impact of thyroxine treatment

BACKGROUND: We have studied the significance of the thyroxine treatment for neuropsychological functioning in young adults with congenital hypothyroidism. SUBJECTS AND METHODS: This is a neuropsychological follow-up study of a three-year cohort of early treated congenital hypothyroidism in Norway (N = 49) at age 20. Siblings comprise the control group (N = 41, 21 years). RESULTS: The patient group performed weaker than the control group on cognitive and motor measures. They reported somewhat more psychosocial problems; fewer completed high school. A more severe hypothyroidism at the time of diagnosis was associated with a larger motor deficit at age 20. Better cognitive function in young adulthood was associated with a higher thyroxine starting dose and serum thyroxine level in the first years of life. Blood samples in young adulthood showed elevated thyrotropin levels in 45% of the patients. INTERPRETATION: This study supports the new guidelines for treatment of congenital hypothyroidism with a higher starting dose of 10-15 microg thyroxine/kg/24 hours. The young adults are in need of better medical follow up.