Newborn Screening for Congenital Hypothyroidism, Victoria, Australia, 1977-1997. Part 1: The Screening Programme, Demography, Baseline Perinatal Data and Diagnostic Classification

Abstract

Clinical, demographic and laboratory data from infants with congenital hypothyroidism (CH) born in the Australian state of Victoria from the commencement of neonatal screening in mid-1977 until December 1988 are reported. These provide a baseline for a 12-year prospective longitudinal study on physical and neuro-psychological outcome until mid-1997, the subject of a second paper. Infants with CH were detected using a primary TT4 screening test. Demographic data were collected prospectively using a clinical assessment protocol. Nearly all affected infants underwent 99m Tc pertechnetate scanning at the initial assessment to determine the underlying aetiology of their hypothyroidism. 704,723 infants were screened and 199 with permanent primary hypothyroidism (one in 3,541) were identified. The most common aetiologies were thyroid ectopia (46%), thyroid aplasia (33%), and 'dyshormonogenesis' (11%). The clinical abnormalities classically described in CH were more evident in infants with aplasia, and the striking female preponderance in infants with thyroid dysplasia (syn. dysgenesis) was confirmed. Other features included increased frequencies of 'dyshormonogenesis' in infants of parents of Middle-Eastern origin and of labour induction in infants with dysplasia. A closed posterior fontanelle was not found in any infant with thyroid aplasia.

Biochemical severity of thyroid ectopia in congenital hypothyroidism demonstrates sexual dimorphism

“…Due to the retrospective nature of our study, we were unable to accurately determine the proportion of children in our study who had familial forms of thyroid dysgenesis. Based on the reported frequency of approximately 2% of familial thyroid dysgenesis (16,24), we would only expect 2 patients in our series of 117 patients with ectopia and athyreosis to have a familial basis, thus making any form of statistical analysis of the familial cases impossible even if we were able to identify them.…”

“…Many questions remain regarding the molecular contributions to the dimorphic physiologies of males and females. It has been suggested that only 2% of patients with thyroid dysgenesis incorporating the spectrum of ectopia and athyreosis have a familial basis (16,24). The female preponderance was observed in sporadic forms of thyroid dysgenesis with almost thrice the number of girls affected (3,6).…”

Factitious Increase in Thyrotropin in a Neonate Caused by a Maternally Transmitted Interfering Substance

“…As per the standard newborn screening procedure (1,2 ), the neonatal screening test was repeated on day 17, and although lower than the previous measurement, the TSH was again above the URL (TSH, 19.6 mIU/L; URL, 10.0 mIU/L). On day 21 of life, the child was euthyroid, had thrived since birth with a current weight of 3600 g, and was feeding well.…”

Hypothyroidism

“…An Australian study has reported that 62% of infants diagnosed with CH have jaundice, 54% have an umbilical hernia, 41% have edema, and 21% have a protruding tongue, whereas only 6% show an enlarged thyroid on palpation. 48 In addition, approximately 15% of CH children also show an increased incidence of major congenital malformations, 48 particularly cardiac (7%) and urogenital (3%) abnormalities.…”