Outcome of lower L-thyroxine dose for treatment of congenital hypothyroidism

Mean High-Dose l-Thyroxine Treatment Is Efficient and Safe to Achieve a Normal IQ in Young Adult Patients With Congenital Hypothyroidism

CONTEXT

The optimal levothyroxine (LT4) dose to treat congenital hypothyroidism (CH) remains unclear, with debate over whether higher starting doses (>10 µg/kg) are necessary and safe for a normal intelligence quotient (IQ).

OBJECTIVE

To examine psychomotor, metabolic, and quality of life (QoL) outcomes in patients with CH treated with a mean high initial LT4 dose.

DESIGN, SETTINGS, PARTICIPANTS

A cross-sectional cohort study of patients with CH identified in the Berlin newborn screening program from 1979 to 2003; 76 patients with CH (mean age, 18 years; mean initial LT4 dose, 13.5 µg/kg) and 40 siblings completed the study.

MAIN OUTCOME MEASURES

Psychomotor (Wechsler Intelligence Test, CNS Vital Signs), QoL (short form-36 Health Survey), anthropometric (body mass index, height), and metabolic (intima media thickness, laboratory parameters) outcomes were compared with those of healthy siblings. Mean values and percentage of episodes of elevated thyroxine (T4) and tri-jod-thyronin (T3) and suppressed thyrotropin (TSH) before age 2 years were analyzed. A meta-analysis of CH treatment studies was performed.

RESULTS

There were no significant differences in IQ, QoL, or other outcome measures in patients with CH compared with controls. Most T4 levels were high before age 2 years and during subsequent testing, but mean T3 and TSH levels remained normal. The meta-analysis showed a significant IQ difference in severe vs mild CH cases only when treatment started with an LT4 dose <10 µg/kg.

CONCLUSIONS

High initial LT4 dosing was effective and safely achieved optimal cognitive development in patients with CH, including those severely affected. Supranormal T4 values during infancy were not associated with impaired IQ in adolescence.

Congenital Hypothyroidism: Optimal Initial Dosage and Time of Initiation of Treatment: A Systematic Review

CONTEXT

Appropriate management of neonates, tested positive for congenital hypothyroidism (CH), in particular, the initial dosage of levothyroxine and the time of initiation of treatment is a critical issue. The aim of this study was to assess all current evidence available on the subject to ascertain the optimal initial dose and optimal initiation time of treatment for children with CH.

EVIDENCE ACQUISITION

In this study, all published research related to the initiation treatment dose and the onset time of treatment in congenital hypothyroidism were reviewed. The searched electronic databases included Medline, Science direct, Scopus EMBASE, PsycINFO, Cochrane, BIOSIS and ISI Web of Knowledge. Additional searches included websites of relevant organizations, reference lists of included studies, and issues of major thyroid and pediatrics journals published within the past 35 years. Studies were included if they were written in English and investigated levothyroxine dose or timing of treatment or both, used for the treatment of children with congenital hypothyroidism.

RESULTS

Two thousand three hundred and seventy-four articles (excluding duplicates) were retrieved from the primary search. After reviewing the titles, abstracts and full-texts of studies, eventually, 22 studies were found that met our inclusion criteria. Amongst these, 17 and 12 evaluated outcomes of different treatment doses and treatment timing, respectively. Overall, the majority of these studies emphasized the initial high dose of levothyroxine and early treatment of newborns with hypothyroidism. There were, however, some studies that disagreed with increasing levothyroxine dose at initiation of treatment.

CONCLUSIONS

Considering the results of this review, apparently there is no difference in opinion regarding the early initiation of treatment, whereas determining the optimal dose of levothyroxine for start of treatment in CH patients still remains a controversial issue, demonstrating the need for further studies, despite the fact that use of high doses can lead to rapid normalization of biochemical indices, although this may cause complications.

Levothyroxine replacement in primary congenital hypothyroidism: the higher the initial dose the higher the rate of overtreatment

BACKGROUND

Congenital hypothyroidism (CH) is the most frequent endocrine disorder during the neonatal period, and a delay in diagnosis and treatment leads to irreversible complications. A high L-thyroxine (LT4) dose is recommended for treatment, while the optimal starting dose is still a matter of debate. The objective of this study was to determine the effects of various starting doses of LT4 on serum thyroid stimulating hormone (TSH) and thyroxine (fT4) at the end of the first month of treatment.

METHODS

A total of 71 patients (37 males, 52.1%) with CH were included in the study. The patients were designated into three sets of subgroups according to the following categorical variables: (i) initial LT4 doses: 6-9.9 μg/kg/day, 10-11.9 μg/kg/day and 12-17 μg/kg/day; (ii) initial TSH levels: 6-9.99 μIU/mL, 10-75 μIU/mL and >75 μIU/mL; and (iii) etiology: dyshormonogenesis and dysgenesis. A fT4 level >2.3 ng/dL±a TSH level <0.5 μIU/mL were considered as overtreatment.

RESULTS

The mean age of the study population was 22.3±13.2 days at diagnosis. At diagnosis, the mean fT4 was 0.84±0.32 ng/dL, and TSH was 39.3±30 μIU/mL. The mean initial dose of LT4 was 10.9±2.9 μg/kg/day. Overtreatment rates were significantly higher in the highest dose group (12-17 μg/kg/day) compared with the lowest dose group (6-9.9 μg/kg/day) (61.5% and 25%, respectively, p<0.05). None of the patients was undertreated.

CONCLUSIONS

In this study, we found that the rate of overtreatment was significantly higher in patients who were given LT4 doses of 12-17 μg/kg/day. Thus, monitoring thyroid functions earlier than one month of treatment is necessary.

Clinical monitoring guidelines for congenital hypothyroidism: laboratory outcome data in the first year of life

OBJECTIVE

To examine whether current recommendations for thyroid status monitoring in children with congenital hypothyroidism (CH) (monthly in the first 6 months and every 3-4 months subsequently) are adequate, or whether monthly monitoring is necessary throughout the first year.

STUDY DESIGN

We reviewed charts of 70 children with CH for initial thyroid-stimulating hormone (TSH), frequency of follow-up, dose changes, and thyroxine (T(4)) and TSH levels in the first year. Need for monthly monitoring was determined on the basis of guidelines to maintain T(4)/free T(4) in the upper half of the normal range and rapidly normalize TSH.

RESULTS

Monthly monitoring was justified in 75% in the first 6 months and 36% in the next 6 months. Children requiring monthly monitoring in the second 6 months had higher baseline TSH (P = .02) and lower T(4) (P = .01) than those not requiring monthly monitoring. Thyroid dysgenesis, starting levothyroxine dose, sex, and ethnicity did not predict requirement for monthly monitoring. Thirty percent of children in the first and second 6 months had ≥1 high TSH level, with a T(4)/free T(4) not in the upper half of the normal range.

CONCLUSION

More than a third of children with CH require monthly monitoring between 6 to 12 months on the basis of study criteria. Current monitoring guidelines may need to be reexamined.

High versus low dose of initial thyroid hormone replacement for congenital hypothyroidism

BACKGROUND

Congenital hypothyroidism (CHT) affects approximately one in 3000 to 4000 infants. CHT is one of the most common preventable causes of learning difficulties. Optimal management of CHT requires early diagnosis and prompt treatment to avoid abnormal neurodevelopmental outcome. One of the main issues in the management of CHT relates to the initial dose of levothyroxine to be used in order to achieve optimal results in terms of intellectual development. Currently, it remains unclear whether high dose thyroid hormone replacement is more effective than low dose in the treatment of CHT. Further research is required to determine an appropriate dose that improves mental and psychomotor developmental outcomes.

OBJECTIVES

To determine the effects of high versus low dose of initial thyroid hormone replacement for congenital hypothyroidism.

SEARCH STRATEGY

Randomised controlled trials were identified by searching The Cochrane Library, MEDLINE and EMBASE and reference lists of published papers.

SELECTION CRITERIA

Randomised controlled clinical trials investigating the effects of high versus low dose of initial thyroid hormone replacement for congenital hypothyroidism were included.

DATA COLLECTION AND ANALYSIS

Both authors independently selected trials, assessed risk of bias and extracted data.

MAIN RESULTS

The initial search identified 1014 records which identified 13 publications for further examination. After screening the full text of the 13 selected papers, only one study evaluating 47 babies finally met the inclusion criteria. Using the same cohort at two different time periods, the study investigated the effects of high versus low dose thyroid hormone replacement in relation to (1) time taken to achieve euthyroid status and (2) neurodevelopmental outcome. The study reported that a high dose is more effective in rising serum thyroxine and free thyroxine concentrations to the target range and earlier normalisation of thyroid stimulating hormone compared to a lower dose. Similarly, full scale intelligence quotient was noted to be significantly higher in children who received the high dose compared to the lower dose. However, the verbal intelligence quotient and performance intelligence quotient were similar in both groups. Growth and adverse effects were not reported in the included trial.

AUTHORS' CONCLUSIONS

There is currently only one randomised controlled trial evaluating the effects of high versus low dose of initial thyroid hormone replacement for CHT. There is inadequate evidence to suggest that a high dose is more beneficial compared to a low dose initial thyroid hormone replacement in the treatment of CHT.

Thyroxine replacement in an animal model of congenital hypothyroidism

This study examined the effects of thyroxine (T(4)) treatment on spatial learning and memory in congenitally hypothyroid (CH) rats. Forty CH male offspring of methimazole-treated dams were randomly divided into three groups: no T(4) (vehicle) treatment (n=12), T(4) treatment commencing on postnatal day (P-) 7 (n=14), and T(4) treatment commencing on P-21 (n=14). Normal male rats were used as a control group (n=14). T(4) was administered daily (sc, 0.02 microg/g) to the treatment groups for 30 days. A water-maze was used to assess behaviour at 42, 70 and 98 days of age. T(4) treatment beginning at P-7 improved learning and memory associated with CH at 70 and 98 days of age but T(4) treatment beginning at P-21 did not improve CH-impaired learning and memory.

Mental development of infants with congenital hypothyroidism: a longitudinal study

The purpose of this study was to assess the relationship between the clinical findings before starting treatment and the development quotient in children treated for congenital hypothyroidism. Patients with congenital hypothyroidism (n = 129) were divided into favorable and unfavorable groups according to intellectual performance. Children with congenital hypothyroidism generally have a similar intellectual outcome to that of healthy children. However, a low birth weight, the presence of complications, and a high serum thyroid-stimulating hormone value are the risk factors for unfavorable cases, who consistently have a development quotient score of less than 100.

Treatment and follow-up of children with transient congenital hypothyroidism

OBJECTIVE

To study the clinical therapy and prognosis in children with transient congenital hypothyroidism (CH).

METHODS

Fifty-seven children with CH diagnosed after neonatal screening were treated with low-dosage levothyroxine (L-T4). Follow-up evaluation included the determination of TT3, TT4 and TSH serum levels and the assessment of thyroid gland morphology, bone age, growth development and development quotients (DQ). A full check-up was performed at age 2, when the affected children first discontinued the L-T4 treatment for 1 month, and one year later. Development quotients were compared with a control group of 29 healthy peers.

RESULTS

The initial L-T4 dosage administered was 3.21-5.81 microg/(kg.d) with an average of (16.25+/-3.87) microg/d. Mean duration of therapy was (28.09+/-9.56) months. No significant difference was found between study group and control group in the DQ test (average score (106.58+/-14.40) vs (102.4+/-8.6), P>0.05) and 96.49% of the CH children achieved a test score above 85. Bone age, 99mTc scans and ultrasonographic findings were all normal, and evaluation of physical development was normal too, as were the serum levels of TT3, TT4 and TSH after one year of follow-up.

CONCLUSION

A L-T4 dosage of 3.21-5.81 microg/(kg.d) was found sufficient for the treatment of transient CH. The treated children showed satisfactory overall mental and physical development at age 2. So it is possible for CH children to stop taking medicine if their laboratory findings and physical development are all normal after regular treatment and 2-3 years of follow-up.

Evolução do programa de triagem neonatal para o hipotireoidismo congênito e fenilcetonúria no Estado de Sergipe de 1995 a 2003

Avaliamos o tempo gasto nas diferentes etapas do Programa de Triagem para o Hipotireoidismo Congênito (HC) e Fenilcetonúria (PKU), sua cobertura e a freqüência em Sergipe, de 1998 a 2003, e comparamos com 1995. A idade da criança na coleta foi 12 ± 11 dias (Média ± Desvio Padrão) em 2003, inferior aos 30 ± 19 dias no 2º semestre de 1995. No 2º semestre/2003, o resultado foi analisado pelo médico com 28 ± 15 dias para o HC e 25 ± 15 dias para o PKU, menor que o tempo utilizado pelo médico no 2º semestre de 1995, 80 ± 40 dias. O tempo, no 2º semestre de 2003, entre o recebimento da amostra da coleta no laboratório e a realização do ensaio foi de 6 ± 4 dias para o TSH e de 3 ± 2 dias para a fenilalanina. A cobertura, em 2003, para o Interior foi de 67% e 85% para a Capital contra 5% e 42% no 2º semestre de 1995, respectivamente. A incidência de 1998 a 2003, no Serviço Público de Saúde de Sergipe para o HC, foi de 1/4850 e para o PKU, de 1/23036. De 1998 a 2003, a terapia foi iniciada com 49 ± 17 e 51 ± 12 dias para o HC e PKU, respectivamente. A redução do tempo nas etapas do programa e o aumento da cobertura indicam uma evolução favorável do referido programa.

Cognition and behavior at school entry in children with congenital hypothyroidism treated early with high-dose levothyroxine

OBJECTIVE

To document cognition and behavior at school entry in these patients. Study design Eighteen children with congenital hypothyroidism (CH; 9 severe and 9 moderate, based on a surface of the knee epiphyses at diagnosis<or >or=0.05 cm(2)) treated from a median of 14 days with a median of 12.0 microg/kg per day of levothyroxine were evaluated at 5 years, 9 months, with the McCarthy Scale and the Questionnaire for Evaluation of Social Behavior, as were 40 control children.

RESULTS

The global IQs at 5 years, 9 months, were similar: medians (range) were 102 (87 to 133), 102 (84 to 135), and 115 (88 to 136) (not significant) for severe CH, moderate CH, and control children, respectively. The behavioral scores of CH children were within the normal range. However, the number of times when plasma TSH was >6.0 mIU/L during treatment was correlated positively with anxiety (P=.02) and inattention (P=.05), whereas the number of times TSH was <0.8 mIU/L was correlated with lower verbal scores (P=.05).

CONCLUSIONS

Children with severe CH treated early with a high dose of levothyroxine have normal global development and behavior at school entry.

Effect of different starting doses of levothyroxine on growth and intellectual outcome at four years of age in congenital hypothyroidism

To evaluate the effect of different initial levothyroxine (LT4) replacement doses on growth and intellectual outcome in patients with congenital hypothyroidism (CH) detected by neonatal screening program, the longitudinal growth and intelligence quotient (IQ) were assessed and compared at 4 years of age in 83 patients with CH. The patients were divided into three groups according to the initial LT4 dose used: (1) group 1 (n = 42) received the previously recommended dose of 6.0-8.0 microg/kg per day; (2) group 2 (n = 21) received a dose of 8.1-10.0 microg/kg per day; (3) Group 3 (n = 20) a dose of 10.1-15.0 microg/kg per day. The IQ, evaluated by the Wechsler Preschool and Primary Scale of Intelligence test at 4 years of age, was significantly higher in group 3 (IQ 98 +/- 9) compared to group 1 (IQ 88 +/- 13; p < 0.05) but not compared to group 2 (IQ 94 +/- 13). However, the IQs were below the normal range (< 85) in six patients from group 2 (28%), but in none of the patients from group 3 (p = 0.03). Patients from group 3, with severe CH at diagnosis, had an IQ (97 +/- 9) at 4 years of age, which was not different from that of patients from the same group with moderate CH at diagnosis (IQ 99 +/- 9). Similar results were also observed in patients from group 2 however, mean IQ scores in these patients (93 +/- 12) were several points lower than those observed in patients from group 3 (95 +/- 15). After the first month of treatment, optimal serum levels of thyroxine (T4) and free thyroxine (FT4) were achieved in all groups, however, only patients from group 3 were able to normalize thyrotropin (TSH) (group 1, 16.0 +/- 12.0; group 2, 9.2 +/- 10.0; and group 3, 2.4 +/- 3.3 mU/L; p < 0.0001). Twelve patients from group 2 treated with an initial LT4 dose above 9 microg/kg per day were able to normalize TSH levels within the first 3 months of life and this resulted in a better IQ (97 +/- 16) compared to the remaining patients from the same group (IQ 90 +/- 9). In the whole group of 83 patients the IQ at 4 years of age was positively correlated to both initial LT4 dosage (r = 0.27, p < 0.02) and FT4 concentrations after the first month of treatment (r = 0.29, p < 0.02), and negatively correlated to TSH concentrations after the first month of treatment (r = -0.27, p < 0.02). No significant differences were observed in height, weight, head circumference, and bone age maturation among the three groups of patients. No clinical signs or symptoms of overtreatment were observed during follow-up in patients receiving the higher LT4 dosage. Our results indicate that high LT4 starting doses rapidly normalize serum TSH concentrations resulting in an improvement of the IQ at 4 years of age, even in patients with severe CH at diagnosis. Growth and bone age maturation are not affected by such a high dose.

Avaliação do programa de triagem para o hipotireoidismo congênito no estado de Sergipe

Nesta pesquisa fizemos uma avaliação da oportunidade nas diversas etapas que compõem o mecanismo de detecção do Programa de Triagem para o Hipotireoidismo Congênito, sua cobertura e a freqüência de casos no serviço público de saúde em Sergipe. Levantamos a idade de todas as crianças (2994) submetidas à triagem para detecção neonatal do hipotireoidismo congênito e fenilcetonúria em suas diversas fases, no período de junho a dezembro de 1995. A idade da criança na coleta do exame, foi de 30±19 dias (média±DP). A idade, quando o resultado da triagem chegou ao centro de saúde, foi de 48±7 dias, quando entregue à família, de 66±18 dias e quando visto pelo pediatra da unidade, de 80±40 dias. Crianças com resultados alterados são referidas para serviços especializados sem nenhum pacto de prioridade. Com relação à cobertura, apenas 5% das crianças do interior do Estado e 42% da capital foram examinadas. A morosidade nas etapas do programa e a baixa cobertura de crianças submetidas ao teste de triagem comprovam a hipótese de que o referido programa de governo não está atingindo seus objetivos principais que são o tratamento oportuno e a cobertura a todas as crianças recém-nascidas, a fim de que sejam prevenidas suas seqüelas.

Influence of timing and dose of thyroid hormone replacement on development in infants with congenital hypothyroidism

OBJECTIVES

To test whether early treatment with a high initial dose of levothyroxine can prevent suboptimal mental development in all neonates with congenital hypothyroidism (CH).

STUDY DESIGN

Sixty-one patients, 27 with severe CH and 34 with mild CH, were treated either early (<13 days) or late (> or =13 days) with either a high initial dose of levothyroxine (> or =9.5 microg/kg/d) or a low initial dose (<9.5 microg/kg/d). With these criteria, 4 treatment groups were formed. The results of the Bayley test, performed at the age of 10 to 30 months and expressed as mental developmental index (MDI) and psychomotor developmental index (PDI), were related to socioeconomic status, treatment group, initial free thyroxine (FT(4)) concentration, and mean FT(4) concentration during the first 3 months of treatment (FT(4)-A) and the ensuing 9 months (FT(4)-B).

RESULTS

Mean (+/- SD) MDI was 113 +/- 14, and mean PDI was 114 +/- 12. In the severe CH group, only the patients treated early with a high initial dose had normal MDI scores (124 +/- 16), whereas the scores of the other groups ranged from 97 to 103. In contrast, all patients in the mild CH group had normal scores (range, 122-125), except those in the group treated late with a low initial dose, whose score was 110 +/- 10. Forty-three percent of the variance in MDI and PDI scores was explained by treatment factors, such as the treatment group, initial FT(4) concentration, FT(4)-A, and FT(4)-B.

CONCLUSIONS

Our data suggest that optimal treatment includes achievement of euthyroidism before the third week of life by initiation of therapy before 13 days with a levothyroxine dose above 9.5 microg/kg/d and maintenance of FT(4) concentrations in the upper normal range during the first year. Thus treated, patients with CH can achieve normal psychomotor development at 10 to 30 months, irrespective of the severity of the disease.

Congenital hypothyroidism: long-term outcome

Although mental retardation associated with congenital hypothyroidism (CH) is prevented by newborn screening and early treatment, affected children still undergo a brief period of thyroid hormone deficiency reflecting etiology of thyroid disease, illness severity, and treatment factors. Because thyroid hormone is essential for normal brain development and because some processes require thyroid hormone in the period when thyroid hormone was lacking, children with CH treated early may still have subtle neurocognitive deficits. As the period when thyroid hormone is needed differs for different brain regions, there may be different types of deficits depending on when thyroid hormone levels were insufficient. Since 1980, we have been following a large cohort of Toronto-based children with congenital hypothyroidism identified by newborn screening from infancy to adolescence. Early findings revealed a 5-10-point decline in IQ, poorer visuomotor and visuospatial abilities, delayed speech and language development, selective neuromotor deficiencies, and poorer attention and memory skills, which were correlated with different disease and treatment factors. Now a comparison between 48 subjects at adolescence and matched controls indicates that deficits persist in visuospatial, memory, and attention domains and these are correlated with severity of early hypothyroidism. Negative relationships between attention indices and thyroxine (T4) elevations at time of testing also suggest a role for thyroid hormone in the regulation of attention.

Neonatal hypothyroidism: treatment and outcome

Systematic neonatal screening for congenital hypothyroidism (CH), which was progressively implemented in industrialized countries over the past 15 to 25 years, has been extremely successful in eradicating severe mental deficiency resulting from CH. However, in the first generation of children diagnosed by screening, the concept that CH has a threshold effect on intelligence was confirmed. In spite of earlier diagnosis through screening, children with severe CH (i.e., those with a marked retardation of bone age and/or a low circulating thyroxine [T4] before treatment) still had clinically significant intellectual sequelae, amounting to a loss of 6 to 19 IQ points. Recent studies suggest that this developmental gap may be closed by treating more rapidly after birth (2 weeks instead of 4-5 weeks in the early years of the screening era) and by using a higher initial dose of levothyroxine (10-15 instead of 5-8 microg/kg per day). This regimen induces transient hyperthyroxinemia, but no clinical signs or symptoms of hyperthyroidism. Longer term follow-up of larger numbers of patients remains necessary to confirm the normalization of intellectual development and the absence of untowards effects of the treatment regimen in children with severe CH.