Vitamin D content in children with short stature due to intrauterine growth restriction against normosomatotropinemia

Abstract

Background. There are no data about the status of vitamin D and its effect on the growth hormone/growth factors axis in prepubertal children with intrauterine growth restriction (IGR). Of particular interest is a group of patients who remain significantly short on the background of a decrease in insulin-like growth factor 1 (IGF-1) levels and normal stimulated release of growth hormone (GH). The purpose of our study was to determine the levels of 25-hydroxycalciferol in the blood plasma of prepubertal children with short stature due to IGR on the background of normosomatotropinemia. Materials and methods. We examined 34 prepubertal children (14 girls and 20 boys) with short stature (average age — 6.95 ± 0.46 years) who had signs of IGR at birth. A symmetrical type of IGR was found in 15 (44.2 %) patients, an asymmetrical type — in 19 (55.8 %). According to the results of functional tests all patients had a normal GH peak release (> 10 ng/ml). Thyroid-stimulating hormone, free thyroxine levels in the blood plasma were determined by the immunoradiometric assay with standard Immunotech® kit (Czech Republic). At the time of examination, all patients were euthyroid. GH, IGF-1 and insulin-like growth factor binding protein 3 (IGFBP-3) levels were determined by enzyme-linked immunosorbent assay using Immulite 2000 Xi kits (Siemens, USA). 25-hydroxycalciferol level was determined by the immunochemiluminescent method (Abbott, USA). The results were evaluated according to the guidelines of the International Society of Endocrinology (2011). Results. It was found that in prepubertal children with IGR signs at birth, the average height standard deviation score (SDS) at the time of the examination was –2.83 ± 0.12. There were no significant differences between the height and body weight in patients with a symmetrical and an asymmetrical types of IGR at the time of examination (p > 0.05). Vitamin D content in the blood plasma of children with IGR signs was 49.70 ± 2.17 nmol/l in the whole group. Vitamin D insufficiency below 75 nmol/l was found in 16 (47 %) patients, and vitamin D deficiency below 50 nmol/l — in 18 (53 %). No significant differences were found between vitamin D values in girls and boys with signs of IGR (51.79 ± 3.38 nmol/l and 48.36 ± 2.86 nmol/l, respectively, p > 0.05). Height SDS in the group of patients with an asymmetrical type of IGR weakly correlates (r = 0.38) with vitamin D content. Vitamin D level significantly differed depending on IGR type (in a symmetrical type — 44.1 ± 3.2 nmol/l, in an asymmetrical type — 54.20 ± 2.56 nmol/l, p < 0.05). IGF-1 SDS in the group of patients with an asymmetrical type of IGR weakly correlated (r = 0.36) with vitamin D level. On the background of a significant decrease in IGFBP-3 content in children with an asymmetrical type of IGR compared to those with a symmetrical type (–1.32 ± 0.07 SDS and –1.00 ± 0.14 SDS, p < 0.05), there was a reduction in IGF-1 levels (–1.62 ± 0.10 SDS and –1.34 ± 0.14 SDS, p = 0.05). Conclusions. Patients born with signs of IGR, even against normosomatotropinemia, may still have significant growth deficit, a sharp decrease in IGF-1 and IGFBP-3 for a long time after birth. The results obtained indicate the presence of hypovitaminosis D in all prepubertal patients who were born with the signs of intrauterine growth restriction. No correlation was found between vitamin D level and the maximum peak of stimulated growth hormone release. However, patients with an asymmetrical type of IGR have a weak correlation (r = 0.36) between IGF-1 SDS and vitamin D content, a significant decrease in the content of IGF-1, IGFBP-3, as well as vitamin D compared to its level in a symmetrical type of IGR. It is recommended to include the determination of vitamin D level in the blood plasma irrespective of the type of disease and the state of somatotropic function in the list of studies for the examination of children with short stature who were born with signs of intrauterine growth restriction.