[Osteocalcin in children of short stature and its nocturnal variations].

Serum osteocalcin (Gla-P) was measured in 65 children with normal stature for age and in 116 children with growth retardation, excluding endocrine disorders, in matched groups according to age: 1-6 years (n = 33); 7-10 years (n = 49); 11-14 years (n = 72); 15-18 years (n = 27). Thirty of these patients were retested at 2 weeks interval. In addition, Gla-P and growth hormone (hGH) were assayed in blood samples obtained every 20 minutes during sleep in 12 children with growth retardation. In younger children, Gla-P levels were significantly lower in patients with growth retardation, when compared with normal children. In contrast, this difference was no longer significant in children above 11, with either normal or delayed puberty. However, important intra-individual variations of Gla-P levels were observed on blood samples obtained at 2 weeks interval. A nocturnal periodicity in Gla-P was found; Gla-P rose slightly during sleep in the patients studied, maximum concentration being reached between 4 and 6 AM. No correlation between integrated concentrations of hGH and Gla-P was found. Gla-P determination may be of interest in the evaluation of young children with short stature. Standardized conditions of blood sampling for Gla-P use in children remain to be determined.