Acid-base Homeostasis in Children With Growth Hormone Deficiency

Abstract

Background. Although the primary use of growth hormone (GH) is to promote linear growth, it is also known to affect many metabolic processes and to influence renal function. In laboratory animals, growth hormone deficiency (GHD) causes a mild metabolic acidosis that is corrected by GH treatment. We observed a patient with GHD who initially presented with acidosis of unclear etiology and corrected the acidosis with GH treatment. Objectives. To determine: 1) whether children with GHD have lower mean serum bicarbonate concentrations than do children with short stature because of other causes; and 2) whether the presence of a low serum bicarbonate concentration increases the probability of GHD among children with short stature. Methods. We collected data from the medical records of 143 children with short stature who had serum electrolyte concentrations measured as part of their initial evaluations, 66 with GHD and 77 with short stature as a result of other causes. We compared mean serum bicarbonate concentrations and bicarbonate standard deviation scores (SDS) between these two groups and determined the probability of GHD for patients according to bicarbonate SDS. Results. The mean serum bicarbonate concentration was significantly lower in patients with GHD (mean standard deviation [SD]; 23.9 [0.4] mEq/L vs 25.2 [0.3] mEq/L) as was the bicarbonate SDS (−0.12 [0.14] SD vs 0.38 [0.10] SD). Twelve (75%) of 16 patients with bicarbonate SDS ≤−1 SD had GHD compared with 7 (28%) of 25 patients with bicarbonate SDS >1 SD. Patients with bicarbonate SDS between −1 SD and 1 SD had an intermediate probability of GHD, 46/102 (45%), similar to the overall prevalence of GHD in the study population (46%). Mean bicarbonate concentrations and bicarbonate SDS increased significantly in 9 patients who had repeat electrolyte measurements during treatment with GH (mean bicarbonate; 21.7 [1.1] mEq/L vs 26.9 [0.59] mEq/L, mean bicarbonate SDS; −1.24 [0.43] SD vs 0.55 [0.27] SD). Conclusions. Serum bicarbonate concentrations are lower in patients with GHD than in patients with short stature as a result of other causes. In addition, serum bicarbonate concentrations rise with GH treatment in patients with GHD. The probability of GHD is increased for patients with bicarbonate SDS ≤−1 SD and decreased for patients with bicarbonate SDS >1 SD. These findings indicate a role for GH in maintaining normal acid-base homeostasis and suggest that GHD should be considered in children whose growth failure is attributed to other causes of acidosis.