Earlier Onset of Treatment or Increment in LT4 Dose in Screened Congenital Hypothyroidism: Which Was the More Important Factor for IQ at 7 Years?

Abstract

Objective: To determine between timing and LT4 dose which was the more important factor for IQ at 7 years in screened congenital hypothyroidism (CH). Methods: 131 children with CH born from 1979 to 1994 and 30 controls were studied. Mean age at recall: 22.8 ± 1.1 days. Mean initial LT4: 5.6 ± 0.1 µg/kg/day. Results: Optimal global IQ (GIQ; 119.0 ± 1.8) was obtained for a recall ≤15 days. Results for a recall after 3 weeks were lower (107.7 ± 2.4). The IQ of infants treated before 21 days (117.1 ± 1.2) was identical to the IQ of controls (117.0 ± 2.3) whereas the IQ of those treated after this threshold was lower (108.6 ± 1.7). No significant differences for GIQ were observed with various initial LT4 doses. Infants treated with a dose of LT4 ≧6 µg/kg/day had a higher performance IQ (117.3 ± 1.8 vs. 112.8 ± 1.2) compared with those treated with a dose <6 µg/kg/day. The severity of CH and socio-economic levels were similar in all groups. Conclusion: In this study, timing appears to be the more important factor for the intellectual outcome.

Children With Congenital Hypothyroidism: Long-Term Intellectual Outcome After Early High-Dose Treatment

“…This is in accordance with the findings of other studies (22,28). This lack of association can be attributed to the early high-dose treatment regimen, which may eliminate the effects of initial dose or onset of treatment as reported by studies using either low dose (Ͻ10 g/kg/d) or late onset of treatment or both (11,29,30).…”

Risk factors for neurodevelopmental deficits in congenital hypothyroidism after early substitution treatment

“…The DQ scores for adaptive behavior, fine motor, gross motor, language, and personal-social behavior were comparable between the patients who began therapy ≤ 20 days after birth and those who began therapy > 20 days after birth (p > 0.05). The DQ scores for adaptive behavior, fine motor, gross motor, language, and personal-social behavior [23]. However, an Australian report showed that the mean full scale IQs were similar between infants who started treatment after 14 days of age and those who started before 14 days of age [24].…”

Wrodzona niedoczynność tarczycy — polskie rekomendacje dotyczące leczenia, monitorowania terapii i badania przesiewowego w specjalnych kategoriach noworodków z wysokim ryzykiem niedoczynności tarczycy

“…The initiation of treatment in the first two weeks of life gives the child a chance for normal intellectual and physical development [8][9][10]. In the most common primary hypothyroidism, levothyroxine preparations (L-T4) are considered to be the most effective.…”

“…Rozpoczęcie leczenia w ciągu pierwszych 2 tygodni życia daje dziecku szansę na prawidło-wy rozwój intelektualny i fizyczny [8][9][10]. W najczęściej występującej, pierwotnej niedoczynności tarczycy uważa się za najkorzystniejsze podawanie preparatów lewoskrętnej tyroksyny (L-T4).…”