Growth Pattern in Juvenile Idiopathic Arthritis in Relation to Insulin Growth Factor-1 and S100A8/9 Protein.

Abstract

Impairment of Growth can result in JIA, which is defined as body height in the lowest third percentile of the population, or body height more than two standard deviations below the mean for the population. Normal growth is a complex interrelation of factors, including genetic, hormonal, and nutritional requirements. In the presence of normal thyroid function, the secretion of pituitary growth hormone and the growth hormone dependent insulin-like growth factors (IGF), particularly IGF-1, form the predominant hormonal axis of postnatal growth. Insulin-like growth factor 1 (IGF1) is an important determinant of muscle mass because it promotes growth and suppresses protein degradation. IGF1 is decreased in rheumatoid arthritis and juvenile idiopathic arthritis because its synthesis is inhibited by inflammation. IGF-1, also called somatomedin C is a protein that acts as a primary mediator of the effects of growth hormone GH, it stimulates systemic body growth, and has growth promoting effects on almost every cell in the body, especially skeletal muscle, cartilage and bone. In addition to insulin like effects, IGF-1 can also regulate cell growth and development especially in nerve cells as well as cellular DNA synthesis. IGF-1 is produced throughout life. The highest rates of IGF-1 production occur during the pubertal growth spurt, the lowest level occur in infancy and old age. S 1008/9 protein also known as Calprotectin is proinflammatory and Ca++ binding protein. This protein is complex and secreted after activation of phagocyte and endothelial cells and it is associated with acute and chronic inflammatory disorder. The S100 A8/9 protein has recently been proposed as "alarmins" which is the endogenous molecule that signal the early phase of tissue and cell damage.