Assessing Renal Function in Children with Congenital Hypothyroidism

Document Type : Original Article (s)

Authors

1 Associate Professor, Department of Pediatrics, Child Health Promotion Research Center, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran

2 Professor, Department of Pediatrics, Endocrine and Metabolism Research Center, Isfahan University of Medical Sciences, Isfahan, Iran

3 Pediatrician, Department of Pediatrics, Child Health Promotion Research Center, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran

4 Associate Professor, Department of Radiology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran

Abstract

Background: Congenital hypothyroidism is a preventable cause of mental retardation. However, less than 10% of children with congenital hypothyroidism are diagnosed at the first month of life based on clinical symptoms. Not using screening programs to diagnose patients would lead to delayed diagnosis and irreparable auditory dysfunction due to cerebral complications. Untreated congenital hypothyroidism causes growth and developmental retardation and can be associated with cardiac and skeletal complications and gastrointestinal anomalies. Renal problems are also among the complications that have been recently attributed to hypothyroidism. Since this hypothesis is still under debate, this study was designed to assess the effects of hypothyroidism on renal function and structure.Methods: This case-control study compared 36 children with congenital hypothyroidism with 38 healthy children during late April 2010 to late October 2011. The study was conducted in Alzahra Hospital affiliated with Isfahan University of Medical Sciences (Isfahan, Iran). After physical examination, blood tests were performed to measure thyroid-stimulating hormone (TSH), thyroxine (T4), creatinine (Cr), sodium (Na), calcium (Ca), potassium (K), magnesium (Mg), cystatin C, and blood urea nitrogen (BUN). Urinalysis was also employed to evaluate microalbuminuria, Cr, Na, K, Mg, and Ca. Glomerular filtration rate (GFR), proximal and distal tubule function, and loop of Henle were then determined. In addition, renal sizes were determined using ultrasound. The control group was selected from the siblings of children with congenital hypothyroidism and healthy children who referred to the pediatric endocrinology ward. The case and control groups were compared in terms of renal function and renal anatomy.Findings: The mean age of subjects in the case and control groups was 9.1 ± 4.1 and 9.2 ± 3.6 years, respectively (P > 0.05). The mean GFRs in the case and control groups were 98.28 ± 12.9 and 98.23 ± 13 ml/min, respectively (P < 0.05). The case and control groups were different in terms of Na excretion fraction (1.01 ± 0.65 vs. 0.77 ± 0.32; P = 0.04), K excretion fraction (12.47 ± 14.1 vs. 7.09 ± 3.8; P = 0.03), and urinary K/Cr ratio (0.81 ± 0.95 vs. 0.46 ± 0.26; P = 0.04).Conclusion: The results of this study showed that although congenital hypothyroidism had no effects on renal sizes in human, it could affect renal tubules. In addition, the effect of the complication on distal tubules was clearer than other tubules. Therefore, conducting further studies in this regard is recommended.

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