[Results of national evaluation tests (primary schools) of CE2 and 6th classes of 73 students with congenital hypothyroidism screened at birth]

Transient hypothyroidism at 3-year follow-up among cases of congenital hypothyroidism detected by newborn screening

OBJECTIVE

To investigate the rate of transient thyroid deficiency and treatment compliance among cases with congenital hypothyroidism diagnosed and followed-up after age 3 years by newborn screening (NBS).

STUDY DESIGN

Cases detected by Michigan NBS between October 1, 2003, and December 31, 2007, and followed-up after age 3 years were included. The χ(2) and Fisher exact tests were used to test differences among followed and lost cases. Logistic regression models were used to investigate predictors of treatment cessation.

RESULTS

Roughly 45% of eligible cases were lost to follow-up, and disease state (transient or permanent congenital hypothyroidism) could not be determined for 12 cases (7.9%). Of the 72 followed cases, 34 (47%) were considered permanent congenital hypothyroidism based on thyroid imaging findings (n = 7) or an increase in medication dosage over time (n = 27). One-quarter of followed cases with congenital hypothyroidism were no longer being treated, and of these, just over 83% stopped treatment without medical supervision. Of 23 cases that underwent a medically supervised trial without thyroid hormone medication, treatment was reinstated in 20. Laboratory confirmation of euthyroidism was available for 6 of 18 cases clinically deemed transient. After adjustment, black race was the strongest predictor of treatment cessation (OR, 9.86; 95% CI, 1.82-53.31). Treatment cessation was also more common among low birth weight infants and those admitted to the neonatal intensive care unit at birth.

CONCLUSION

We recommend that NBS programs include long-term follow-up through at least age 3 years to determine treatment compliance and disease permanence. Further research is needed to determine ideal follow-up program operations and reassessment methods for congenital hypothyroidism disease permanence. Guidelines that provide evidence-based reassessment methods would be beneficial for the healthcare providers of children with congenital hypothyroidism.

Genetics, clinical management and natural history of congenital hypothyroidism

Congenital hypothyroidism has an incidence of 1:3000-4000 newborns. In the past, it was a common cause of mental retardation, although newborn screening has improved the prognosis. Several transcription factors are crucial to the early organogenesis of the thyroid, including TITF1, FOXE1, PAX8 and HHEX. Nevertheless, a small minority of humans with congenital hypothyroidism carry mutations in these genes. Long-term follow-up studies show that with appropriate therapy, the mental and physical development of congenital hypothyroidism patients is in the normal range, although somewhat delayed when compared with appropriate controls. Critical issues of treatment include early diagnosis and rapid correction of hypothyroidism by ensuring rapid initiation of treatment and rapid normalization of thyroid-stimulating hormone levels, especially in cases of severe congenital hypothyroidism. There has been recent question of the need to treat premature infants with hypothyroxinemia but no elevation of the thyroid-stimulating hormone concentration. Numerous controlled studies of the short- and long-term effects of thyroid hormone supplementation have not shown a consistent benefit in this group of patients. Future research will investigate further the genetic underpinnings of the condition. There is a worldwide need to prevent congenital hypothyroidism by ensuring adequate dietary iodine and to develop infrastructure to diagnose and treat congenital hypothyroidism in developing countries.

Neonatal screening for congenital hypothyroidism in Hessen, Germany: efficiency of the screening program and school achievement of 129 children at an age of 8-12 years

Status and school achievement of 129 children born in Hessen between 1988 and 1992 and notified by a repeatedly elevated concentration of TSH in neonatal screening were evaluated. Interviews of mothers, teachers and pediatricians were used to score the development and educational achievements, respectively. A total of 298,175 newborns were screened and the incidence of permanent congenital hypothyroidism (PCH) was 1: 3,313 (n = 90). The female/male ratio was 1.37:1. In the 69 PCH cases with complete data, athyreosis (52%), hypoplasia (32%), dyshormogenesis (9%) and ectopia (7%) were identified as etiologies. The mean age at start of therapy decreases from day 15 in 1988 to day 9 in 1992; however, 27% of PCH children showed reduced psychomotor development as scored by their pediatrician and 11% attended a special school for educationally subnormal children. Approximately 25% of the children had lower educational achievements irrespective of the school type. Our finding of a relatively high percentage of PCH children with subnormal development points to a failure in disease management. A follow-up program including repeated serum TSH monitoring and yearly examinations by pediatric endocrinologists and supervision by the regional screening center is necessary to ensure the long-term efficacy of neonatal screening for congenital hypothyroidism.

Children with congenital hypothyroidism and their siblings: do they really differ?

OBJECTIVE

Although favorable outcome is typically described in follow-up studies of children with congenital hypothyroidism (CH) identified by newborn screening, IQ reductions and persistent cognitive deficits are still reported. These findings are accounted for by disease and treatment variables as well as methodologic factors including choice of comparison group. Although siblings are ideal because they control for genetic and environmental influences, by definition they have different ages when tested, which can also introduce bias. Because we followed children with CH and their siblings over an extended period of time, there were a number of occasions when both groups were tested at the same age. The purpose of this study was to compare the results of children with CH and their unaffected siblings at the same age and with the same test.

METHODS

The sample consisted of 42 children with CH detected between 1975 and 1985 and their 42 siblings, all of whom were tested with the McCarthy or Wechsler Intelligence Scale for Children-Revised (WISC-R) intelligence tests. Nineteen pairs of children were evaluated at 6 years with the McCarthy, and 30 pairs of children were evaluated at 7 or 9 years with the WISC-R. Recorded for children with CH were disease etiology, bone age and thyroxine levels at diagnosis, age at onset of treatment, and starting dosage of levothyroxine.

RESULTS

Paired t tests revealed that the CH group scored lower than siblings by 8.1 IQ points on the McCarthy and 6.2 points on the WISC-R. Factors contributing to the size of the CH-sibling IQ difference were (1) the etiology of hypothyroidism, reflecting the larger differences by those with athyreosis or an ectopic gland than dyshormonogenesis, and (2) the starting dosage of levothyroxine, with those initially treated with >or=8.2 microg/kg per day having smaller CH-sibling differences than those given lower starting doses. There were no effects of bone age, thyroxine levels at diagnosis, or age at treatment onset.

CONCLUSION

Children with CH treated early in life due to newborn screening may have reduced IQ relative to siblings.

Congenital hypothyroidism: influence of disease severity and L-thyroxine treatment on intellectual, motor, and school-associated outcomes in young adults

OBJECTIVE

To describe intellectual, motor, and school-associated outcome in young adults with early treated congenital hypothyroidism (CH) and to study the association between long-term outcome and CH variables acting at different points in time during early development (CH severity and early L-thyroxine treatment levels [0-6 years]).

METHODS

Neuropsychological tests were administered to all 49 subjects with CH identified during the first 3 years of the Norwegian neonatal screening program (1979-1981) at a mean age of 20 years and to 41 sibling control subjects (mean age: 21 years).

RESULTS

The CH group attained significantly lower scores than control subjects on intellectual, motor, and school-associated tests (total IQ: 102.4 [standard deviation: 13] vs 111.4 [standard deviation: 13]). Twelve (24%) of the 49 CH subjects had not completed senior high school, in contrast to 6% of the control subjects. CH severity (pretreatment serum thyroxine [T4]) correlated primarily with motor tests, whereas early L-thyroxine treatment levels were related to verbal IQ and school-associated tests. In multiple regression analysis, initial L-thyroxine dose (beta = 0.32) and mean serum T4 level during the second year (beta = 0.48) predicted Verbal IQ, whereas mean serum T4 level during the second year (beta = 0.44) predicted Arithmetic.

CONCLUSIONS

Long-term outcome revealed enduring cognitive and motor deficits in young adults with CH relative to control subjects. Verbal functions and Arithmetic were associated with L-thyroxine treatment variables, suggesting that more optimal treatment might be possible. Motor outcome was associated with CH severity, indicating a prenatal effect.