CONGENITAL HYPOTHYROIDISM: THE EFFECT OF STOPPING TREATMENT AT 3 YEARS OF AGE

69 children were detected by a low thyroxine (T4) and/or elevated thyrotropin (TSH) on neonatal screening to have congenital hypothyroidism (CH). Of these, 55 are 3 years of age or older. Thyroid scanning at diagnosis showed 16/55 were athyrotic (A), 21/55 had goiters (G) and 18 with ectopic (E) glands. E were excluded because of the anatomic abnormality. 22 of the remaining 37 showed a secondary rise of TSH to >10 mU/L confirming the diagnosis during the first 3 years. In 15 with continuous TSH suppression, thyroxine was discontinued at age 3 years or more. In the first 6, TSH was measured at 6 weeks: in 5/6 it was >60, in 1 with G-CH, TSH was 7 at 6 weeks and 15 at 8 weeks. Symptoms of hypothyroidism occurred in 4/6. TSH was then measured at 3 weeks and was >60 in the remaining 10. When the TSH was elevated, T4 was 40±39 nmol/L (±SD). In all patients with A-CH or G-CH, the diagnosis was confirmed either by a secondary rise of TSH while on treatment or by a TSH rise at 3-6 weeks after discontinuing therapy. In this group, thyroid screening appears to be 100% specific. Hypothalamic-pituitary responsiveness and hypothyroid symptoms return very rapidly after stopping L-T4 therapy. We recommend TSH measurement 3 weeks after stopping L-T4 in children with CH >3 years in whom confirmation of the initial diagnosis is desirable.