Effect of initial levothyroxine dose on neurodevelopmental and growth outcomes in children with congenital hypothyroidism.

Objectives: We designed a multicentre open prospective randomized trial to evaluate the risk-benefit profile of two different initial treatment schemes with levothyroxine (L-T4), 10-12.5 µg/kg/day vs 12.6-15 µg/kg/day, on growth and neurodevelopmental outcomes in children with congenital hypothyroidism (CH) detected by neonatal screening to identify the best range dose to achieve optimal neurocognitive development. Design patients and methods: Children detected by neonatal screening were randomly assigned to receive an initial L-T4 dose of 10-12.5 µg/kg/day (Low) or 12.6-15 µg/kg/day (High). All patients underwent periodical clinical examination with measurement of growth parameters and measurement of TSH and FT4. Neurocognitive development was evaluated at the age of 24 months using Griffiths Mental Development Scales (GMDS) and cognitive and behavioral assessment was performed at 48 months of age using Wechsler Preschool and Primary scale of Intelligence (WIPPSI-III). The study was registered with clinicaltrials.gov (NCT05371262). Results: Treatment schemes below or above 12.5 µg/kg/day were both associated with rapid normalization of TSH and thyroid hormone levels in most patients with no differences in the risk of over- and under-treatment episodes in the first months of life. Growth parameters were normal and comparable between the two groups. Developmental quotients at 24 months of age were normal in both groups (Low 100.6 ± 15.5 vs High 96.9 ± 16.6). Likewise, at 4 years of age IQ and subtest scores were comparable between patients from Low and High (Total IQ 104.2 ± 11.4 vs 101.0 ± 20.3, Verbal IQ 103.9 ± 11.5 vs 98.7 ± 15.1, Performance IQ 105.3 ± 10.4 vs 100.3 ± 19.8). 6/45 CH patients (13.3%) showed a total IQ below 85 (73.7 ± 5.9) regardless of age at diagnosis, L-T4 starting dose, time of FT4 and TSH normalization and episodes of over and undertreatment. Worse socioeconomic status and delayed bone age at diagnosis were the only predictors of an increased risk of having suboptimal IQ at 24 and IQ at 48 months. Conclusions: Our results indicate that initial treatment with L-T4, 10-12.5 µg/kg/day vs 12.6-15 µg/kg/day, are both associated with normal growth and neurodevelopmental outcomes in children with CH detected by neonatal screening. Further studies with a long-term follow-up on a larger number of patients are needed to confirm these results. Clinical trial registration: https://clinicaltrials.gov/ct2/show/NCT05371262?term=NCT05371262&draw=2&rank=1 identifer NCT05371262.

Treatment of congenital hypothyroidism: comparison between L-thyroxine oral solution and tablet formulations up to 3 years of age.

OBJECTIVE: Oral solution and tablet formulations of levothyroxine (L-T4) are both used in the treatment of congenital hypothyroidism (CH). However, few studies and with a limited follow-up period have been published comparing these two formulations in children. DESIGN: The aim of this multicenter study was to compare the effectiveness of L-T4 oral solution (with ethanol as excipient) and tablet formulation in children with CH up to 3 years of age. METHODS: Children diagnosed with CH between 2006 and 2015 were enrolled and divided into two groups according to the L-T4 formulation used: solution in drops (group D) or tablets (group T). Auxological parameters, thyroid-stimulating hormone (TSH) and free thyroxine (FT4) values and L-T4 dose were collected at diagnosis and at 15 days, 1, 3, 6, 12, 24 and 36 months of treatment. The developmental quotient (DQ) at 1 and 3 years of age was evaluated using Griffiths' Scale. RESULTS: In this study, 254 children were enrolled among which 117 were treated with solution and 137 with tablets. Auxological parameters, dose and thyroid function values at diagnosis, 3, 6, 12, 24, 36 months were not significantly different. TSH at 15 days (P = 0.002) and 1 month (P = 0.009) was significantly reduced in group D. At 2-year follow-up, median TSH was significantly lower in group T (P = 0.03). No statistical difference was detected between the median DQ; however, group D showed lower values in the language subscale at 12 months and in eye-hand coordination at 36 months. CONCLUSIONS: Both therapeutic strategies are effective in the treatment of CH. A higher risk of overtreatment in the first months of therapy seems to be associated with oral solution L-T4; therefore, a different strategy should be considered when starting and adjusting the dose. No negative effects on cognitive development were observed. The data obtained are encouraging but long-term follow-up is needed.

Congenital hypothyroidism treatment in infants: a comparative study between liquid and tablet formulations of levothyroxine.

AIMS: To compare the effects of liquid and tablet formulations of levothyroxine (L-T4) in 78 newborns with congenital hypothyroidism (CH). METHODS: 39 patients received liquid L-T4 (group A) and 39 patients received tablets (group B). Thyroid-stimulating hormone (TSH) and free thyroxine (fT4) were measured and L-T4 dose recorded at onset of therapy and during the first year of treatment. Developmental quotient (DQ) was assessed by Griffiths' mental development scales at 12 months of age. RESULTS: Gestational age, birth weight, screening TSH, etiology and severity of CH, age at onset of therapy and median initial L-T4 dose were similar in both groups. fT4 concentration normalized before 10 days of treatment in all patients. Normalization of TSH concentration was achieved after 7-10 days of therapy in 87% of group A patients and in 82% of group B patients. Group A patients had significantly lower TSH values compared with those of group B at 7-10 days (p = 0.05) and 6-8 months (p = 0.043) of treatment, despite similar L-T4 dose and fT4 concentration. Mean DQ scores were within normal range in all patients. CONCLUSION: We confirmed the efficacy and safety of both formulations. The TSH inhibition trend when using liquid L-T4 may be linked to a higher absorption in comparison to the tablets.