Growth hormone/insulin-like growth factor-1 system and vitamin D content in children with growth hormone deficiency

Abstract

In a significant number of patients with short stature, the presence of disorders in the growth hormone/growth factor system has been established. First of all, this concerns such a disease as growth hormone deficiency (GHD), in which there is a sharp decrease in the levels of growth hormone (GH), insulin-like growth factor-1 (IGF-1) and its binding protein. It cannot be ruled out that vitamin D deficiency can affect the growth of a child at different stages of development. The role of vitamin D in the pathogenesis of various forms of pathology of growth and physical developmen has not been studied. The aim — to study the state of the GH/IGF-1 system and the vitamin D content in children with GHD. Material and methods. 66 prepubertal children (44 boys, 66.7%) with GHD were examined. Isolated GHD was established in 54 children (81.82%), 32 children (59.26%) had the full form of GHD, 22 children (40.74%) — the partial form of GHD. Multiple pituitary hormone deficiency (MPHD) was diagnosed in 12 children (18.18%). The levels of GH and IGF-1 were studied by the method of solid-phase immunoenzyme analysis using «Immulate 2000 XPi Immunoassay System» («Siemens», Germany). The level of 25-hydroxyvitamin D in blood serum was determined with immunochemiluminescence method on microparticles («Abbott», USA). An evaluation of the results was carried out according to the recommendations of the International Society of Endocrinologists: ≤50 nmol/L — vit. D deficiency; 50-75 nmol/L — vit. D insufficiency; >75 nmol/L — the norm, >100 nmol/L — hypervitaminosis D. Results. All the examinees had a significant growth retardation: height-standard deviation score was minus 2.34±0.10. Peak of GH response to provocative testing in children with MPHD was significantly lower than in children with an isolated form of GHD (p<0.05), however both indicators showed the presence of a significant deficit of GH. In patients with MPHD, the average level of IGF-1 was 63.71±17.58 ng/mL which significantly differed from that in the isolated form of GHD (p<0.05). 71.21% of the examined had hypovitaminosis D (63.70±3.98 nmol/L), which corresponded to the degree of this vitamin insufficiency. 83.33% of children with MPHD and 68.49% with isolated form of GHD had hypovitaminosis D. Against the background of vitamin D deficiency, patients with MPHD had significantly lower level of IGF-1 than those with isolated GHD (p<0.05). Conclusions. It was found that in most cases (71.21%) children with GHD had hypovitaminosis D; vitamin D deficiency was observed in 37.88%, vitamin D insufficiency — in 33.3% of patients. Hypovitaminosis D was observed more often in patients with MPHD (83.33%) than in those with isolated GHD (68.49%) due to a greater proportion of people with vitamin D deficiency (58.33%). Existing deficiency of vitamin D in children with GHD was associated with the lowest indicators of IGF-1, which confirms the close relationship between vitamin D and IGF-1. With MPHD against the background of severe vitamin D deficiency, a significantly (p<0.05) smaller peak of GH response to provocative testing and a significantly lower IGF-1 content were observed. Diagnosis and therapy of GHD require a preliminary evaluation and monitoring of 25-hydroxyvitamin D content in the blood serum of patients in order to obtain a correct picture of the state of the GH/IGF-1 system.