Background: This study was undertaken to explore the clinical outcome and prognosis of subclinical hypothyroidism detected by newborn screening.
Methods: Newborn screening was conducted at 1156 health care institutions in Zhejiang Province from October 1999 to September 2006. Included were (1) infants who had thyroid-stimulating hormone (TSH) ≥ 20 mU/L, and normal or lower normal levels of triiodothyronine (T(3)) and thyroxine (T(4)) and (2) infants with TSH between 5.6 mU/L and 20 mU/L at a confirmatory examination and follow-up showing TSH levels ≥ 20 mU/L or delayed reduction in T(4) levels. These infants were considered as having subclinical hypothyroidism and levothyroxine (L-T(4)) at an initial dose of 3-5 μg/kg per day was administered. The levels of TSH and T(4), developmental quotient (DQ), and index of growth were evaluated.
Results: A total of 204 infants met our criteria for subclinical hypothyroidism, with an incidence of 1/8809. After 2-4 weeks of standard therapy, serum TSH level dropped to normal and T(4) reached a higher normal level in all the 204 infants. Evaluations of 60 patients after 2 years of therapy showed that their average DQ was 101 ± 14.61, and body weight and height were within the normal ranges. Bone age test for 54 patients revealed normal development in 44, slightly retarded development in 7, and advanced development in 3.
Conclusions: Newborns with high TSH levels should be given particular attention to ensure early diagnosis. A L-T(4) dose of 3-5 μg/kg per day was effective in the initial treatment of subclinical hypothyroidism.