Vitamin D and Calcium Homeostasis in Infants with Urolithiasis.

The incidence of urolithiasis in infants is unknown. The aim of this study was to investigate clinical characteristics, nutrition, calcium, phosphate, 25-hydroxyvitamin D (25(OH)D), alkaline phosphate, and parathyroid hormone in infants with urolithiasis. There were 32 infants (23 boys and 9 girls) of the mean age of 6.4 ± 3.7 months (range 2-12 months), with diagnosis of urolithiasis enrolled into the study. Boys were younger than girls (5.3 vs. 9.1 months, respectively; p < 0.05). The infants were receiving prophylactic vitamin D3. Twenty-one of them were fed with milk formula, 9 were breastfed, and 2 were on a mixed diet. The major clinical symptoms consisted of irritability in 19 (59%) and urinary tract infection in 6 (19%) infants. Hypercalcemia and hyperphosphatemia were detected in the serum in 30 (94%) and 19 (60%) infants, respectively. The serum calcium level was higher in boys than girls (10.8 vs. 9.8 mg/dL, respectively; p < 0.05). Four (12.5%) infants had increased activity of alkaline phosphatase. The serum level of 25(OH)D was high in 3 (9%), low in 2 (6%), and normal in 27 (85%) infants. Parathyroid hormone was low in eight (25%) infants. Hypercalciuria and hyperphosphaturia were found in 11 (34%) boys and 8 (25%) girls. Family history of urolithiasis was positive in eight (25%) infants. We conclude that urolithiasis occurs in infancy more often in boys fed with milk formula and in those who received vitamin D supplementation. Hypercalcemia, hyperphosphatemia, and hypercalciuria are the most common changes present in clinical metabolic tests.