Long-term effects of primary hypothyroidism on renal function in children

Objectives To examine the impact of hypothyroidism on renal function in children and the effect of thyroid hormone therapy on the long-term outcome. Study design The glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were studied in 31 patients with symptomatic acquired hypothyroidism (age, 11 +/- 3.3 years) and in 50 healthy children (age, 10.5 +/- 4.5 years). Children with hypothyroidism were examined before starting thyroxine therapy and I week and 1, 3, and 6 months after starting thyroxine therapy. 13 patients were reinvestigated at 6, 12, 18, 36, and 60 months after initiating thyroxine therapy. Results GFR and ERPF were <-2 SD of control levels in 58% and 45%, respectively, of children investigated before or within 1 week after starting thyroxine therapy. 31% and 6% of the children studied I to 6 months after thyroxine therapy had a GFR and ERPF <-2 SD. Moreover, when GFR and ERPF values were analyzed as percent of control mean, both measurements were reduced to an equal extent. At the last investigation, 1 to 5 years after start of treatment, the GFR was still significantly lower in children with hypothyroidism than that in control subjects. Conclusion Acquired hypothyroidism during childhood may have a long-term impact on renal function.