Insulin-like growth factor I (IGF-1), also known as Somatomedin C, is a polypeptide hormone similar in structure to insulin and primarily produced in the liver. It is one of the main mediators of the actions of growth hormone in promoting muscular and skeletal growth. Because of its similarity to insulin, it weakly activates the insulin receptor and has insulin-like effects when present in large quantities. Blood levels of IGF-1 are low in young children, peaking during the pubertal growth spurt and then declining steadily with age. Growth hormone (GH) stimulates IGF-1 production: unlike GH, levels of IGF-1 do not fluctuate throughout the day, and therefore IGF-1 levels reflect average daily GH levels. It is particularly important to test for IGF-1 during GH supplementation to ensure that levels are within the expected physiological range. IGF-1 production is affected by nutritional factors: low levels are seen in malnutrition or anorexia, and IGF-1 can be used as a sensitive indicator to monitor nutritional repletion. IGF-1 testing can be used by dentists to assess cervical stage of patients and determine whether a patient has attained or passed the peak pubertal growth, predict residual facial skeletal growth, and thus properly time orthodontic procedures. Low IGF-1 levels have been associated with increased cardiovascular disease risk, especially in individuals with diabetes, because of its role in vascular protection. Reference range levels in blood spot are 100—300 ng/mL, and are dependent on age.
IGF-1 Blood Spot Test Specifications