FREQUENCY AND NECESSITY OF THYROID-FUNCTION TESTS IN NEONATES AND INFANTS WITH CONGENITAL HYPOTHYROIDISM

0Objective. The American Academy of Pediatrics recommends frequent thy roid function tests in infants and children with congenital hypothyroi dism (CH). Data supporting the recommended frequency are lacking. This review was conducted to assess the validity of these recommendations. Methods. The thyroxine (T4) and thyroid-stimulating hormone (TSH) lev els of 50 neonates diagnosed between 1988 to 1993 were reviewed to ass ess the length of time on a specific dose of levothyroxine. Results. 1 ) Changes in the dose of levothyroxine occurred 35 times during the fi rst year of life for the 39 children treated with .025 mg/day, five ti mes during the first year of Life for the 9 children treated with .037 5 mg/day, and three times during the first year of life for the 2 chil dren treated with .050 mg/day. 2) These dose changes occurred at varyi ng time intervals. 3) The T4 and TSH levels obtained at visits requiri ng dose changes were statistically different from the T4 and TSH level s obtained at the previous two visits. The T4 and TSH levels at the tw o visits before the change in dosage did not differ statistically. Con clusions. 1) An initial levothyroxine dose of .0375 mg/day requires fe wer dose changes than a dose of .025 mg/day. 2) A lack of statistical change in T4 or TSH levels obtained at visits before the change-in-dos e visit and the variable time span between dose changes necessitate fr equent monitoring regardless of the dose of levothyroxine, the previou s T4 or TSH levels, or the length of time at a specific dose. 3) These data support the recommendations of the American Academy of Pediatric s regarding the frequency of thyroid function studies during the first 2 years of life.