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

Clin Endocrinol (Oxf). 2013 Dec;79(6):832-7. doi: 10.1111/cen.12228. Epub 2013 May 27.


Objective: To examine a large population of infants with mild neonatal hyperthyrotrophinaemia (MNH) and determine prevalence, clinical characteristics and treatment history.

Methods: Retrospective study of infants with MNH followed at The Hospital for Sick Children between 2000 and 2011. MNH was defined by an abnormal newborn screen followed by thyroid-stimulating hormone (TSH) between 5 and 30 mU/l and normal free T4 (FT4) on confirmatory tests.

Results: Mild neonatal hyperthyrotrophinaemia represented 22·3% of patients (103/462; 60 boys, 43 girls) within our clinic. Incidence increased from two of 20 in 2000 to 31 of 74 cases in 2010. Seventy eight percent of patients started L-thyroxine (initial dose: 8·3 ± 2·5 mcg/kg). The treated group had higher confirmatory TSH levels (P = 0·001) and had undergone thyroid scintigraphy more often (P = 0·0001) compared with the nontreated group. Evidence of overtreatment was detected in 45% of thyroid function tests obtained during treatment. Among the treated infants who had reached 3 years of age, 45% (N = 14) underwent a trial-off medication. Compared with those not trialled-off therapy, these infants were less likely to have had dose escalations during treatment (P = 0·001). The trial-off treatment was successful in 50% of cases. In the subset of infants with confirmatory TSH >10 mU/l, trial-off therapy was successful in 40%. None of the assessed variables predicted success of trial-off therapy.

Conclusions: Mild neonatal hyperthyrotrophinaemia is an increasingly common diagnosis. It is more common in males and is often transient, but predictors of success of trial-off therapy were not identified. Further studies are needed to determine optimum L-thyroxine dosing and to determine whether treatment improves neurocognitive outcomes.

MeSH terms

  • Congenital Hypothyroidism / blood*
  • Congenital Hypothyroidism / drug therapy
  • Congenital Hypothyroidism / epidemiology
  • Female
  • Humans
  • Infant, Newborn
  • Male
  • Neonatal Screening
  • Ontario / epidemiology
  • Prevalence
  • Retrospective Studies
  • Thyrotropin / blood*
  • Thyroxine / blood
  • Thyroxine / therapeutic use


  • Thyrotropin
  • Thyroxine