[Phosphorus-calcium metabolism and plasma 25-hydroxycholecalciferol in intestinal malabsorption]

Abstract

One hundred and four children aged 0-15 years, with suspicion of malabsorption were studied. They had a proximal jejunal biopsy and, at the same time, the following measurements: 25-hydroxycholecalciferol (25-OH-CC), calcium, phosphorus and serum alkaline phosphatase, bone age on X-ray of the left hand and wrist, cortical thickness of the 2nd, 3rd, 4th metacarpal bones. For the analysis of the results, the patients were divided into two groups according to the season (winter vs. summer). None of the patients in either group had clinical or radiological signs of rickets. The following results were obtained: 1. The 25-OH-CC serum levels were significantly lower during the winter than during the summer months. This was observed more frequently in the cases with atrophy of the jejunal mucosa. 2. During the summer, the 25-OH-CC serum levels were not different in the cases with normal or pathological mucosa. This demonstrates the importance of the skin synthesis of vitamin D during the summer months. 3. The mean of the serum calcium levels was significantly lower in the group of children with atrophy of the jejunal mucosa than in children with normal intestinal biopsy. The serum calcium levels were not correlated with the serum 25-OH-CC levels. 4. The serum phosphorus levels were significantly lowered during the winter months in the children aged 0-3 years with pathological jejunal biopsy. 5. The serum alkaline phosphatase levels were lowered in cases of total atrophy of the jejunal epithelium cells. 6. Cortical thickness of the metacarpal bones becomes thinner with the progression of the alteration of the jejunal epithelium cells, independently of season or age. However, only the group of children aged 0-3 years studied during the winter months and with total atrophy of the jejunal mucosa have a significantly diminished cortical thickness of the metacarpal bones. The lowering of the calcium levels and the decrease of the cortical thickness are probably secondary to an impaired intestinal absorption of calcium. In the syndrome of malabsorption, the integrity of the jejunal epithelial cells seems to play a more important role than a vitamin D deficiency in the genesis of this calcium malabsorption.