Persistence of Mild Hyperthyrotropinemia after Discontinuation of Three-Year Course of Low-Dose L-Thyroxine Therapy in Infants with Borderline Hypothyroidism

Abstract

Abstract. Treatment plan for neonates with borderline hypothyroidism (persistent hyperthyrotropinemia with normothyroxinemia) has not been established. In this study, changes in thyroid function after discontinuation of low-dose L-thyroxine (L-T4) supplement in infants with the condition were evaluated. Fourteen infants with hyperthyrotropinemia at neonatal screening had repeated hyperthyrotropinemia (>8 mU/L) with normothyroxinemia. TSH response was exaggerated at TRH testing. The subjects were treated with low-dose L-T4 (3 to 9 mg/kg/day) for 2.2 to 6 years, and euthyroid status was maintained. After discontinuation of therapy, mild hyperthyrotropinemia persisted up to 24 months, while serum FT4 remained within the lower half of the normal range. TSH response to TRH stimulation, which tended to be exaggerated 1 month after discontinuation, became lower 6 to 12 months later. RAIU and thyroid scintigraphy were normal in all subjects. No patient developed hypothyroxinemia, although mild elevation of TSH lasted rather long after discontinuation of low-dose L-T4 therapy. Administration of L-T4 was not resumed provided the subjects were followed at regular interval. Further long-term investigation is needed to define whether re-administration is necessary or not.

Neonatal hyperthyrotropinemia: population characteristics, diagnosis, management and outcome after cessation of therapy

“…Over 40% of the HT patients in our study were eventually normalized their FT 4 (i.e. had t‐HT), which is in partial agreement with some studies 3,26 and in contrast to others 4,5 . In a longitudinal study of thyroid function in 44 children with mild HT at neonatal screening, Leonardi et al.…”

l-thyroxin treatment in infants with hyperthyrotropinaemia: 4-year experience

“…During the follow-up, we observed that low-dose l-T4, (2-5 lg/kg/day) was sufficient for treatment. Although there is no satisfactory knowledge in the literature about the dose of l-T4 to be used in hyperthyrotropinaemia, low dose l-T4 was used, similar to our study, in babies with borderline hypothyroidism (15,16). Our patients were followed up at 8 weeks intervals due to the risk of hyperthyroidism.…”

Mild neonatal hyperthyrotrophinaemia: 10‐year experience suggests the condition is increasingly common but often transient

“…Literature on MNH is sparse, with few studies reporting outcomes on small numbers of patients . The natural history of this condition is not well defined, and published results are contradictory regarding the percentage of patients requiring permanent replacement …”