The Key Role of Newborn Thyroid Scintigraphy With Isotopic Iodide (123I) in Defining and Managing Congenital Hypothyroidism

Abstract

ABSTRACT. Background. Thyroid imaging with isotopic iodide ( 123 I) or technetium Tc 99m pertechnetate has been available for decades but is not routinely used in newborn infants diagnosed with congenital hypothyroidism (CH). Among clinicians who believe that presence, absence, or abnormal location of a thyroid does not alter management of CH, imaging is not advocated for anatomic diagnosis of CH.Objective. To define the role of thyroid scintigraphy in diagnosing and managing newborn CH.Methods. Results. Of the 210 infants with CH receiving scintigraphy, 90 (43%) had eutopic (normal-appearing) thyroid diagnosed, and 120 (57%) had ectopic or absent gland (25% ectopic, 32% absent) diagnosed. Of these 210 infants, ethnicity was known in 198; of these, 76 (38%) were Latino/Hispanic, and 122 (62%) of the infants were nonLatino/non-Hispanic. Prevalence of CH differed between ethnic groups in our population of >700 000 newborn infants; total prevalence of CH was 1 per 3139. Prevalence of CH in Latino/Hispanic infants was highest at 1 per 1750 infants (1:1357 females, 1:2463 males). Prevalence of CH in non-Latino/non-Hispanic infants was 1 per 4648 infants (1:3500 females, 1:6914 males). Given that the total Kaiser Permanente infant population was ϳ19% Latino/ Hispanic, the percentage of Latino/Hispanic infants with CH was significantly higher than expected. Dysplastic thyroid was more common in Latino/Hispanic females (69%) than in non-Latino/non-Hispanic females (52%). The female-to-male ratio of patients with CH was 1.9:1. Among the 210 infants with CH, normal thyroid was diagnosed more by 123 I scintigraphy (49% of cases) than by scintigraphy using technetium Tc 99m pertechnetate (31% of cases). Use of technetium Tc 99m pertechnetate could have diagnosed dysplastic thyroid in some cases that would be considered eutopic had 123 I been used. Eight familial cases of CH were identified.Comments. CH, a heterogeneous disorder with prevalence influenced by familial, ethnic, and gender factors, is more common in Latino/Hispanic females. When present, a eutopic thyroid is more likely to be detected by 123 I scintigraphy; this method is therefore preferred over scintigraphy using technetium Tc 99m pertechnetate for optimal management of CH. Parents can then be counseled on either the certainty of lifetime therapy (for dysplastic thyroid) or the possibility of later discontinuing therapy (for eutopic thyroid, because CH may be transient in these children). If the dysplastic thyroid gland is absent or ectopic (usually a small sublingual gland), parents can be told that the infant will need lifetime thyroid therapy. If the thyroid gland is present in the normal position (eutopic) and the condition is transient (as shown by controlled withdrawal of thyroid in older children), lifelong treatment may not be needed. Parents rightly expect this maximal clinical and laboratory information in the immediate newborn period. Some clinicians hesitate to recommend neonatal scintigraphy for children with CH because of concern about delaying ...

Trends in Incidence Rates of Congenital Hypothyroidism Related to Select Demographic Factors: Data From the United States, California, Massachusetts, New York, and Texas

“…One clue may come from the study of Schoen et al, 6 who evaluated the role of thyroid scintigraphy in diagnosing and managing CH in the newborn period. In a population of Ͼ700 000 newborns in California, there were 249 newborns with a confirmed case of CH, of which 210 received neonatal thyroid scintigraphy to determine the presence, absence, or abnormal location of the thyroid gland.…”

“…Causes of most congenital defects of thyroid location or structure are not known, but multiple epidemiologic studies have revealed several consistent trends in associated factors, particularly the newborn's race, ethnicity, sex, birth weight, and gestational age. CH has been reported as more common among Hispanic [4][5][6] and Asian and Native Hawaiian or other Pacific Islander (ANHOPI) 4,5,7 newborns and less common among non-Hispanic black newborns than among non-Hispanic white newborns. 4,5,8 CH occurs more often in girls than in boys, generally with a ratio of 2.…”

Nuclear Medicine in the First Year of Life

“…Untreated congenital hypothyroidism is one of the most common preventable causes of mental retardation (24). Causes of neonatal hypothyroidism include thyroid agenesis, dysgenesis, or ectopia (25); dyshormonogenesis due to inborn errors in thyroid hormone synthesis (26,27); and transient infantile hypothyroidism caused by maternal thyroid-blocking antibodies, maternal antithyroid medications, or iodine exposure (28). In North America, congenital hypothyroidism has an incidence of approximately 1 in every 3,000-4,000 births, with approximately a 2:1 female predominance (24,27).…”

“…Causes of neonatal hypothyroidism include thyroid agenesis, dysgenesis, or ectopia (25); dyshormonogenesis due to inborn errors in thyroid hormone synthesis (26,27); and transient infantile hypothyroidism caused by maternal thyroid-blocking antibodies, maternal antithyroid medications, or iodine exposure (28). In North America, congenital hypothyroidism has an incidence of approximately 1 in every 3,000-4,000 births, with approximately a 2:1 female predominance (24,27). Nearly all new cases of infantile hypothyroidism in North America and Europe are now detected by neonatal laboratory screening for hypothyroidism, which facilitates prompt evaluation and early institution of thyroid hormone replacement therapy to prevent neurocognitive damage.…”

Incidence and Risk Factor of Permanent Hypothyroidism in Preterm Infants

“…Several imaging studies including thyroid ultrasonography and thyroid scan can determine the underlying causes of hypothyroidism and we can expect the natural course of the thyroid function [5,22]. In addition, it can permit parents to be counseled on either the certainty of lifetime therapy.…”