Type 3 renal tubular acidosis associated with growth hormone deficiency

Background: We identified two boys with type 3 renal tubular acidosis (RTA) and growth hormone deficiency and we sought to differentiate them from children with classic type 1 distal RTA. Methods: We reviewed all children <6 years of age with RTA referred over a 13-year period and compared the growth response to alkali therapy in these two boys and in 28 children with only type 1 distal RTA. Results: All children with type 1 RTA reached the 5th percentile or higher on CDC growth charts within 2 years of alkali therapy. Their mean height standard deviation score (SDS) improved from -1.4 to -0.6 SDS and their mean mid-parental height (MPH) SDS improved from -0.6 to 0 SDS after 2 years. In contrast, the boys with growth hormone deficiency had a height SDS of -1.4 and -2.4 SDS after 2 years of alkali and the MPH SDS were both -2.6 SDS after 2 years of alkali therapy. Growth hormone therapy accelerated their growth to normal levels and led to long-term correction of RTA. Conclusions: A child with type 1 RTA whose height response after 2 years of alkali therapy is inadequate should undergo provocative growth hormone testing.