Borderline congenital hypothyroidism in the neonatal period

Neonatal thyroid function born to mothers living with long-term excessive iodine intake from drinking water

OBJECTIVE

The effects of long-term excessive maternal iodine intake on neonatal thyroid function are less known. This study aimed to assess the effects of maternal excessive iodine intake from drinking water on thyroid functions of both mothers and their neonates.

DESIGN AND METHODS

This observational study was performed in high iodine (HI) areas and adequate iodine (AI) intake areas, including 384 healthy pregnant women in late gestation (mean week 39·3 ± 1·6 weeks) and their newborns. Blood and urine samples were obtained from pregnant women, while cord blood samples were obtained from neonates. Urinary iodine concentration (UIC) and thyroid function were evaluated.

RESULTS

The median maternal UIC was 1241 and 217 μg/l in HI and AI areas, respectively (P < 0·001). The concentrations of serum thyroid-stimulating hormone (TSH), free triiodothyronine (FT3) and free thyroxine (FT4) in neonates in HI areas were 7·33 mIU/l (range 5·47, 11·06 mIU/l), 2·93 ± 0·59 and 15·03 ± 1·92 pmol/l, respectively, while that were 4·71 mIU/l (range 3·96, 6·04 mIU/l), 2·31 ± 0·28 and 16·50 ± 1·35 pmol/l in AI neonates (P < 0·05). Similar changes were also observed in neonates in HI areas when excluding the effect of maternal thyroid autoimmunity. Cord blood TSH concentration (r = 0·31, P = 0·001) and FT3 concentration (r = 0·43, P = 0·001) were positively correlated with maternal UIC. Cord blood FT4 concentration was negatively correlated with maternal UIC (r = -0·25, P = 0·001). Mothers living in HI areas (β = 0·296, 95% CI: 0·163, 0·255) and with subclinical hypothyroidism (β = 0·360, 95% CI: 0·034, 0·175) contributed to elevated cord blood TSH concentration in neonates, while male neonates were more likely to present with higher TSH concentration compared with female infants (β = -0·760, 95% CI: -0·119, -0·033).

CONCLUSIONS

Excessive iodine intake during pregnancy was associated with an increased rate of hyperthyrotropinaemia in neonates and their mothers, especially in male neonates.

Correlation between unconjugated bilirubin and total cholesterol in the sera of 1-month-old infants

AIM

To investigate why breastfed infants are more likely to have prolonged jaundice than formula-fed infants.

METHODS

Serum unconjugated bilirubin (UCB), total cholesterol (TC) and triglyceride (TG) were measured for 102 infants of 1 month. Enrolled infants were 42 breastfed, 40 mixed-fed and 20 bottle-fed infants. Statistic analyses for relationship among UCB, TC, TG, perinatal factors and post-natal factors were performed for these infants.

RESULTS

In correlation analyses UCB was correlated with peak transcutaneous bilirubin value in neonatal period (TcBn) (r = 0.612, P < 0.0001) and with TC (r = 0.383, P < 0.0001). When analyses of covariance (ANCOVA) for UCB were performed using TcBn as the covariate, the results indicated that there was neither significant main nor interaction effect of feeding method on UCB, and that main and interaction effects of TC on UCB were significant when TC was categorised into two groups (≤150 mg/dL and >150 mg/dL).

CONCLUSIONS

It is suggested that both neonatal hyperbilirubinemia and subsequent higher plasma TC are associated factors for prolonged jaundice.

L-thyroxin treatment in infants with hyperthyrotropinaemia: 4-year experience

Hyperthyrotropinaemia, in which normal levels of T4 occur in association with raised thyroid stimulating hormone (TSH), is usually picked up on neonatal screening. High TSH level can continue for a long time in some of the cases. There is no consensus concerning the follow-up or treatment plan for hyperthyrotropinaemia. In this study, results of a 4-year follow-up of 36 cases who had been medically treated are discussed. Low-dose (5 microg/kg/day) L-thyroxin treatment was carried out in 36 cases that had 5 mU/l or higher TSH and showed exaggerated response to TRH test. Dose was decreased to 2-3 microg/kg/day in 24 of these patients during 6 months follow-up. The drug was stopped in three cases because of the development of biochemical hyperthyroidism. Denver developmental assessment test was applied to all cases at the end of the third year. All patients showed a normal development in relation to their age. According to our results, cases with hyperthyrotropinaemia need to be followed regularly for a long time and a need for low-dose L-thyroxin treatment may exist at ages varying from patient to patient.

Congenital hypothyroidism: a review of current diagnostic and treatment practices in relation to neuropsychologic outcome

Because thyroid hormone is essential for normal brain development, children born with congenital hypothyroidism who lack thyroid hormone during a circumscribed period of early development are at risk of brain damage and mental retardation. Since the advent of newborn screening programs in the 1980s, the diagnosis and treatment of this condition are now provided in the first 2-3 weeks of birth in most regions. While this is usually sufficient to prevent mental retardation, the children so identified attain mildly reduced IQs from expectation, and may still experience subtle and specific neurocognitive deficits. Their particular deficits are related to the brief period of thyroid hormone insufficiency they undergo, especially factors reflecting the severity of hypothyroidism at the time of diagnosis, the duration of hypothyroidism in infancy, and thyroid hormones at time of testing. In this article, we review the specific kinds of deficits demonstrated by children with congenital hypothyroidism who were diagnosed by screening and treated early, as well as the factors associated with their disease and its management that contribute to these deficits. The disease-related factors that will be reviewed will include the etiology of hypothyroidism and severity of disease at the time of diagnosis, while the treatment-related factors will include age at onset of therapy, starting and subsequent dose levels, compliance, and treatment-adequacy issues. Also examined will be the effects of hormone levels at the time of testing. In addition, the role of moderating variables such as social, genetic, and environmental influences, as well as the child's gender, will be discussed. Furthermore, several new issues including the quality of subsequent management, ultimate outcome, and pregnancy will be additionally reviewed. In conclusion, while outcome in congenital hypothyroidism is substantially improved by screening, affected children do still experience mild neuropsychologic deficits. To reduce the impact of persisting deficits, further research is needed to determine the optimal starting dose for the different etiologies, guidelines for subsequent management, and alternative therapies. Moreover, now that the original samples are reaching adulthood and, in females, childbearing age, further research is also needed regarding treatment during pregnancy in women with congenital hypothyroidism, as is research to determine how this population ultimately fares in adulthood.