Neurophysiological study of peripheral nerves in newborn infants with congenital hypothyroidism. Value in the surveillance of replacement therapy

The authors studied prospectively with electrophysiological means, peripheral nerve maturation of 18 neonates with congenital hypothyroidism compared to 18 controls. Before replacement therapy, a large reduction of sural nerve action potential amplitude and of Hoffmann's reflex was observed. It was accompanied by a moderate reduction in nerve conduction velocity. These results imply a myelinic and even more an axonal pathology. It is related to the anatomical type of hypothyroidism and to serum T4 deficiency. It is transient and disappears after 6 months of hormonal replacement therapy. In conclusion, this study gives new informations on the consequences of congenital hypothyroidism on peripheral nerves.     

Analysis of failures of screening for congenital hypothyroidism by the assay of TSH in capillary blood

Screening for congenital hypothyroidism was started in France in 1979. The system was rapidly extended to the whole country and works very efficiently. The number of children who escaped the system is very small. However, these children represent a severe failure of the system. From 1980 to 1983, 32 cases escaped the screening. Retrospective analysis of these cases should help in improving the present system.     

Thyrotropin (TSH) secretion in L-thyroxine treated children: assessment by a ultrasensitive TSH immunoradiometric assay

The clinical usefulness of the measurement of basal TSH by an ultrasensitive assay (IRMA) versus the TRH test has been challenged in 49 children treated with L-thyroxine. They were given suppressive or replacement therapy depending on the underlying disease. An absent response of TSH to TRH could be predicted from a basal TSH value less than 0.1 mU/l in 88.8% of the cases, while only in 77.7% from a basal TSH value = 0.1 mU/l. A basal TSH value found in the range of the normal children always predicted a normal TRH test. We conclude that a sensitive TSH assay has some clinical application in monitoring L-thyroxine therapy, but can not absolutely replace the TRH test.     

Skeletal maturation during thyroxine treatment in children with congenital hypothyroidism

Heyerdahl S, Kase BF, Stake G. Skeletal maturation during thyroxine treatment in children with congenital hypothyroidism. Acta Prediatr 1994;83:618–22. Stockholm. ISSN 0803–5253
The aim of this investigation was to study if bone age development (assessed by the Greulich & Pyle atlas) was related to L-thyroxine treatment in 47 children with congenital hypothyroidism, treated early and according to general recommendations. In spite of frequent delay in skeletal maturation at diagnosis, the delay in mean bone age at a mean chronological age of 1.5 years was slight (0.5 months), and 30% of the variation in bone age SD score (SDS) at 1.5 years was accounted for by the dose of L-thyroxine and serum thyroxine during the first year. The children with a bone age within ± 1 SDS had a prescribed mean dose of L-thyroxine per kg body weight from 3 to 12 months of age of 5.4 ± 1.7 pg/kg/day, and their mean serum thyroxine concentration during the first year was 175 ± 29 nmol/l. We conclude that bone age at 1.5 years of age was positively correlated with the dose of L-thyroxine and the serum thyroxine concentration during the first year. This supports the general use of bone age assessments as a complement to other treatment variables in the follow-up of children with congenital hypothyroidism.     

Maternal TSH-receptor antibodies and TSH antibodies in screening for congenital hypothyroidism

Serum samples from 30 mothers who had given birth to at least one child with a positive neonatal thyrotropin (TSH) screening test were analysed for TSH-receptor antibodies. One mother with hypothyroidism after thyroiditis who had two sons who had had transient congenital hypothyroidism, showed significantly elevated concentrations of TSH receptor blocking IgG antibodies in her serum. The three daughters of another mother had neonatal hyperthyrotropinaemia but normal thyroid hormone levels. This woman had elevated serum levels of TSH but was clinically and biochemically euthyroid. The apparent hyperthyrotropinaemia in this family was due to an artifact in the TSH radioimmunoassay caused by maternal anti-TSH IgG antibodies. It is obvious that placental transfer of maternal IgG antibodies to the thyroid TSH receptor is one cause of transient congenital hypothyroidism. Likewise, maternal IgG directed against TSH interferes with radioimmunoassays of TSH and the results may be falsely interpreted as hyperthyrotropinaemia. It is concluded that in neonatal hyperthyrotropinaemia analysis of the mother's serum is indicated, and that maternal TSH receptor blocking antibodies must be considered as a cause of congenital hypothyroidism, especially if the mother has a history of thyroid dysfunction.     

Definitive diagnosis in children with congenital hypothyroidism

OBJECTIVES: To investigate the definitive diagnosis and underlying causes of congenital hypothyroidism (CH) in eligible children through the use of a standardized protocol. STUDY DESIGN: Children > or =3 years of age with CH without an identified permanent cause underwent a diagnostic algorithm. Eligible subjects had an anatomically normal thyroid or had not undergone imaging studies. After thyroxine was discontinued for 4 weeks, thyroid function tests and a thyroid ultrasound were obtained. An abnormal ultrasound was followed by a (99m)Tc thyroid scan. A perchlorate washout test was performed in subjects with a normal ultrasound but abnormal thyroid function tests. Children with normal results were followed for 1 year. RESULTS: Of 33 children, 17 were boys. Nine (27%) had an absent or ectopic thyroid, 12 (36%) had dyshormonogenesis, and 12 (36%) had transient CH. Average thyroxine dose before medication discontinuation was 2.9 +/- 0.83 microg/kg in permanent cases versus 2.0 +/- 0.53 microg/kg in transient (P <.002). No complications from discontinuation of thyroxine occurred. CONCLUSIONS: A significant percentage of children with CH have a transient requirement for thyroid hormone. A standardized protocol with thyroid ultrasonography is a safe and sensitive approach to a trial off of thyroxine in select patients.     

Diagnostic Re-evaluation of children with congenital hypothyroidism

Objectives  

To investigate the causes of congenital hypothyroidism in children more than 3 years of age and to document the frequency of transient vs permanent hypothyroidism.     

先天性甲状腺功能减退症患儿DUOX2基因突变的研究

目的 研究先天性甲状腺功能减退症(congenital hypothyroidism, CH)患儿DUOX2 基因突变类型和特点,并初步探讨基因型- 表现型的关系,为CH 患儿的基因诊断和基因治疗提供理论依据.方法 从10例CH 伴甲状腺肿大患儿外周血白细胞中提取基因组DNA,采用PCR 扩增和直接测序的方法对DUOX2 全部外显子进行基因突变检测.结果 在1 例患儿中发现DUOX2 基因第28 外显子cDNA 的3632 位点发生了G>A 的突变(c.G3632A),导致第1 211 密码子的精氨酸变为组氨酸(p.R1211H).在3 例患儿中发现DUOX2 基因第17 外显子cDNA 的2 033 位点发生了T>C 的突变(c.T2033C),导致第678 密码子的组氨酸变为精氨酸(p.H678R).此两种突变均为杂合型的错义突变.结论 CH 患儿存在DUOX2 基因杂合突变,该杂合突变可能引起蛋白质功能的改变从而导致CH;基因型与表现型的关系尚不明确,需要进一步的研究.     

Intellectual development in children with congenital hypothyroidism in relation to recommended thyroxine treatment

The relationship between the treatment serum thyroxine level and intellectual development at 2 and 6 years was investigated in 46 Norwegian children with congenital hypothyroidism identified by neonatal screening. The level of serum thyroxine during the first 2 years was positively correlated with the Mental Development Index at 2 years of age (Bayley Scales of Infant Development) and the Verbal IQ at 6 years of age (Wechsler Preschool and Primary Scale of Intelligence). Children with a mean serum thyroxine level greater than 180 nmol/L (14 micrograms/dl) during the first year had a significantly higher Mental Development Index at 2 years and Verbal IQ at 6 years than children with serum thyroxine values less than 129 nmol/L (10 micrograms/dl). Boys had a lower Mental Development Index at 2 years of age than girls (86.9 vs 105.1; p less than 0.001) and a higher frequency of elevated serum levels of thyroid-stimulating hormone during the first year (p = 0.001). No signs of toxic effects of a high hormone level at the time of IQ assessment were detected. However, high serum levels of thyroxine at ages 2 to 4 years in girls were related to lower Performance IQ at age 6 years. The results demonstrate that the serum level of thyroxine is of importance in relation to intellectual development. Thyroxine levels above the upper reference range during the first 2 years were related to best intellectual development at 2 and 6 years.     

Incidence of febrile convulsions in children with congenital hypothyroidism

Brain excitability has been inconsistently reported to be increased both in hypo- and hyperthyroidism, but there have been few studies on the effects of thyroid hormones on brain excitability in children. With this in mind, we investigated the incidence of febrile convulsions (FCs) among patients with congenital hypothyroidism, who have been taking L - thyroxine since the age of 1 month. The incidence of FCs among congenital hypothyroid patients was 1.6% (1/63) which was significantly low ( p < 0:05) compared with that of normal control children who visited our hospitals as outpatients (28/341, 8.2%) and that of others (322/3301, 9.8%) investigated 33 years ago in the same area. The incidence of FC among siblings of the 63 patients (7/74, 9.5%) was not statistically different from the controls. At least 8 of the 126 parents (6.4%) had experienced FC, however, only one child was affected in the 8 families. In conclusion, it seems likely that patients with congenital hypothyroidism on regular L -T4 replacement are less prone to experience FC. More studies on the incidence of convulsive disorders in children with thyroid diseases are needed to clarify the effects of thyroid hormones on brain excitability.     

早期治疗对先天性甲状腺功能减低症患儿智力及体格发育的影响

目的：比较治疗开始时间不同的先天性甲状腺功能减低症（congenital hypothyroidism, CH）患儿治疗后智力发育、体格发育水平的不同,以寻求改善患儿预后的最佳治疗时间。方法：对2008年9月至2011年9月经新生儿疾病筛查确诊为CH,并在出生后3个月内开始应用甲状腺激素治疗的CH患儿49名,按开始治疗时间分为两组：生后1个月内治疗组（n=26）及1～3个月治疗组（n=23）。分别于6个月、1岁、2岁时,检测两组患儿体格发育情况,应用Gessell 发育量表评估智力发育商（DQ）及采用免疫荧光法测定甲状腺功能。结果：两组经甲状腺激素长期治疗,6个月、1岁、2岁时游离三碘甲状腺原氨酸（FT3）、游离甲状腺素（FT4）及促甲状腺素（TSH）水平差异无统计学意义（P>0.05）,但1个月内治疗组患儿的身长、体重均明显高于1～3个月治疗组,差异有统计学意义（P0.05）。结论：CH开始治疗时间影响患儿智力发育和体格发育;生后1个月内开始治疗者,智力及体格发育优于1～3个月开始治疗者。     

Height prognosis in children with late-diagnosed congenital hypothyroidism.

It is a general belief that early and adequate thyroid hormone replacement achieves normalization of growth as well as disappearance of clinical sings and symptoms of hypothyroidism. Due to the lack of comprehensive growth studies, height prognosis has remained controversial in late-diagnosed hypothyroidic children. The limited number of previous studies have suggested permanent height deficit in these children. In this study we present longitudinal growth and final height of 20 children (14 females and 6 males) in whom the duration of hypothyroidism before onset of therapy varied from three to 12.6 years. The etiological distribution of cases revealed ectopic thyroid tissue in nine cases, agenesis in seven, and dyshormonogenesis in four cases. At the time of the diagnosis all hypothyroidic children had severe growth retardation (mean height SDS +/- SD -3.95+/-1.07) due to prolonged hypothyroidism. Although the catch-up spurt corrected an important part of the initial height deficit in all patients, only nine patients reached or exceeded their target height, and the final height of five patients remained below 2 SD of mean. Despite treatment, prolonged hypothyroidism may result in compromised adult height in some patients. The contributing factors to this height deficit may include the duration of hypothyroidism, the height deficit at the time of the diagnosis, etiological differences and the diminished potential for catch-up growth in late-diagnosed hypothyroidism.