The thyroid-kidney connection

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Screening for congenital hypothyroidism has been nearly universal in the United States for quite some time. Recognizing affected newborns and promptly instituting therapy has saved thousands of children from the adverse developmental outcomes of late-recognition of hypothyroidism.

Most congenital hypothyroidism results from thyroid dysgenesis. Recently, defects in a number of developmentally expressed genes have been identified in thyroid dysgenesis; some of these genes are also involved in development of the urinary tract. Thus, it is reasonable to suspect that there could be an association between abnormal development of the thyroid and urinary tract abnormalities. Some brief reports have suggested this.

In the current issue of The Journal, Kumar et al report a study in which they mined a comprehensive registry of congenital malformations maintained by the New York State Department of Health. This work shows a greater than ten-fold risk of urinary tract anomalies among children with congenital hypothyroidism. Some of these (eg, hypospadius) are obvious on physical examination, and others (eg, hydronephrosis) are not always consequential. Nonetheless, some of the associations are so striking that it is hard to argue with the authors' recommendation that screening ultrasonography should become a part of the management of children with congenital hypothyroidism.