Kidney growth in children with congenital hypothyroidism.

The effect of hypothyroidism on kidney size has not been studied in children. The aim of this study was to examine the role of congenital hypothyroidism and levothyroxine (L-thyroxine) treatment on renal growth. Forty children with congenital hypothyroidism and 37 healthy controls were prospectively included. The mean age of patients was 8.2+/-4.7 years. Patients had lower height and weight standard deviation scores compared with controls. The mean L-thyroxine initial age and treatment duration were 37.0 and 60.5 months, respectively. In 62.5% of patients, L-thyroxine was initiated after 6 months of age, and 60.0% of patients had severe hypothyroidism. Patients had lower kidney length and total kidney volume compared with controls (P < 0.05). No significant differences were found in kidney volume/body weight and kidney volume/ body height ratios between patients and controls (P > 0.05). Multiple regression analysis showed significant relationship between relative kidney volume and average free thyroxine level (P < 0.05). No significant differences in kidney sizes were found between patients who had L-thyroxine initiated before and after 6 months of age or between mild/moderate and severe hypothyroidism at diagnosis (P > 0.05). In conclusion, normal renal growth can be accomplished with L-thyroxine replacement despite considerable delay in treatment initiation and/or severe hypothyroidism.