Renal and Urinary Tract Anomalies in Congenital Hypothyroidism
Newborn screening for congenital hypothyroidism (CH) is one of the major achievements of preventive medicine, as the condition occurs frequently (1/3000~4000 newborns). An early diagnosis and treatment prevents brain damage and the ensuing mental retardation. It is well known that CH has increased incidence of congenital malformations of heart, gastrointestinal, and skeletal systems. However, the prevalence of congenital renal and urologic anomalies on CH has not been well established.
Kumar et al reported that children with CH have significantly increased risk of congenital renal and urological anomalies. They investigated the prevalence of congenital renal and urologic anomalies in children with CH as compared to children without CH. Analysis of Congenital Malformation Registry data showed 980 children with CH and 3,661,585 children without CH born in New York State (1992-2005). Children with CH had a significantly increased risk of congenial renal and urological anomalies with the odds ratio (OR) of 13.2 (10.6-16.5). The other significantly increased defects and prevalence rates in patients with CH were cardiac, gastrointestinal, and skeletal (Table). Analysis of matched data (CH data from New York State newborn screening; 1,538 children with CH and 3,654,033 children without CH) also confirmed an increase of congenital renal and urologic anomalies with an OR of 4.8 (3.7-6.3). There are limitations of their study; the Congenital Malformation Registry is complied on the basis of hospital-generated data and is limited to children under 2 years of age. Therefore, there may be an underestimating of the true prevalence of congenital renal and urologic anomalies.
Hydronephrosis, UPJ obstruction, hypospadias, renal dysplasia, and renal agenesis were especially significant. Therefore, they suggested that CH children should be evaluated for the presence of congenital renal and urologic anomalies by a renal ultrasound examination.
Hydronephrosis, UPJ obstruction, hypospadias, and renal dysplasia and renal agenesis were especially significant. Therefore, they suggested that CH children should be evaluated for the presence of congenital renal and urologic anomalies by a renal ultrasound examination.
This is a very interesting article; it provides important information for physicians who care for patients with CH and elucidates the high incidence of congenital renal and urologic anomalies. Early detection of these anomalies may prevent or delay the risk of renal damage and developing end-stage kidney disease. The paper also provides data regarding the prevalence and odd risk ratios of cardiovascular, gastrointestinal, and skeletal anomalies in CH.
The causes of CH are: thyroid agenesis or hypoplasia, which accounts for 20% to 40% of the cases; ectopic thyroid, which accounts for 45% to 60%; and dyshormonogenesis, which accounts for the remaining 10% to15% of cases. However, Kumar’s observation did not discerned the association differences of congenital renal and urologic anomalies among these types of CH; they reported that mutations in PAX8, TITF1, and FOXE1 genes have been associated with CH in patients with either isolated thyroid dysplasia or thyroid dysplasia with associated malformations involving kidney, lung, forebrain, and palate.
Hydronephrosis was the major defect in CH while hypospadias was most seen in the general population. The renal and urologic anomalies except hypospadias are not found on a routine physical examination, but can be easily detected by a renal ultrasound examination. Hypospadias can be easily diagnosed on a routine physical examination. Therefore, they recommended a routine renal ultrasound examination in CH.
Yoshikazu Nishi, MD