Combined ultrasound and isotope scanning is more informative in the diagnosis of congenital hypothyroidism than single scanning

Abstract

Background: Thyroid imaging is helpful in confirming the diagnosis of congenital hypothyroidism and in establishing the aetiology. Although isotope scanning is the standard method of imaging, ultrasound assessment may be complementary. Aim: To determine the strengths and weaknesses of thyroid ultrasound and isotope scanning in neonates with thyroid stimulating hormone (TSH) elevation. Methods: Babies from the West of Scotland with raised capillary TSH (.15 mU/l) on neonatal screening between January 1999 and 2004 were recruited. Thyroid dimensions were measured using ultrasonography, and volumes were calculated. Isotope scanning was carried out with a pinhole collimator after an intravenous injection of 99m-technetium pertechnetate. Results: 40 infants (29 female) underwent scanning at a median of 17 days (range 12 days to 15 months). The final diagnosis was athyreosis (n = 11), ectopia (n = 12), hypoplasia (n = 8; 3 cases of hemi-agenesis), dyshormonogenesis (n = 5), transient hypothyroidism (n = 2), transient hyperthyrotropinaemia (n = 1) and uncertain status with gland in situ (n = 1). 6 infants had discordant scans with no isotope uptake but visualisation of thyroid tissue on ultrasound. This was attributed to TSH suppression from thyroxine (n = 3); maternal blocking antibodies (n = 1); cystic degeneration of the thyroid (n = 1); and possible TSH receptor defect (n = 1). Conclusions: Isotope scanning was superior to ultrasound in the detection of ectopic tissue. However, ultrasound detected tissue that was not visualised on isotope scanning, and showed abnormalities of thyroid volume and morphology. We would therefore advocate dual scanning in newborns with TSH elevation as each modality provides different information.

Etiological evaluation of primary congenital hypothyroidism cases

“…The prevalence of PCH is 1/2000-4000 in neonatal screening programs (1-3). The female/male ratio is 1.1-2:1 (3,8,9,(17)(18)(19)(20). In Turkey, the prevalence of PCH was found as 1/650 as a result of screening programs performed between 2008 and 2010 and the female/male ratio was similar (17).…”

“…The mean age at the time of diagnosis in various studies was 11-12 days. In our country, the mean age at the time of diagnosis was found 19.2 days in 2008, whereas it decreased to 15.7 days in 2010 (17,19,20). The most common clinical finding in cases of primary congenital hypothyroidism is prolonged jaundice (2,16).…”

Space–time clustering of elevated thyroid stimulating hormone levels

“…The sensitivity and specificity of tests such as isotope scanning is suboptimal with potentially misleading information generated by factors such as early thyroxine therapy [18]. 4.…”

“…There is no definitive test or tests that can identify the underlying thyroid gland abnormality in this condition. Even the combination of isotope scanning and ultrasonography does not reveal an underlying diagnosis in all infants [16,18].…”

Contribuição da dosagem de tireoglobulina e de exames de imagem para o diagnóstico de hipotireoidismo congênito: pesquisa dos genes PAX8 e receptor do TSH na disgenesia tireoidiana

“…O valor de corte para definir um teste de perclorato positivo permanece duvidoso e variável de acordo com os trabalhos. Pode-se também dividir o defeito na organificação do iodo em parcial ou completo de acordo com o resultado do teste [69]. O defeito é considerado parcial quando a descarga de iodo encontra-se entre 10 a 90% e total quando é maior que 90% [70].…”