Abstract
Introduction: The purpose of this study was to develop the use of a biologic marker, insulin-like growth factor (IGF-1), as an indicator for the timing and intensity of mandibular growth. This was done by measuring annual changes in mandibular length and studying how they relate to blood-spot IGF-1 measurements and cervical stages. Methods: Twenty-five patients (12 female, 13 male) from an orthodontic population were longitudinally evaluated for annual IGF-1 level, cervical stage, and mandibular length. The patients' follow-up periods ranged between 1 and 5 years. A total of 43 annual time intervals were gathered (17 female, 26 male). Annual mandibular growth was related to changes in blood-spot IGF-1 levels over each observation period. Results: When the whole sample was pooled into 1 group, we found a statistically significant mild to moderate correlation between the percentages of change in mandibular length and in IGF-1 levels (r = 0.4, P = 0.008). When the sample was divided based on whether the IGF-1 levels were increasing or decreasing at each yearly interval, the group with ascending IGF-1 levels had significantly more mandibular growth than did the group with descending IGF-1 levels (3.5 and 1.3 mm, respectively; P = 0.026). The ascending group had a moderate to high correlation between average IGF-1 levels and the amount of mandibular growth for each observation period. Observation periods with ascending IGF-1 levels and an average level greater than 250 mu g per liter had significantly greater annual mandibular growth than did the rest of the patients with ascending IGF-1 levels (5.6 and 2.1 mm, respectively). Conclusions: Blood-spot IGF-1 testing is a promising tool for predicting the timing and the intensity of the mandibular growth spurt without the restrictions involved with radiographic techniques for assessing skeletal maturity. More research is necessary to validate these results in a different population by using more advanced imaging tools and a larger sample size. The relationship between IGF-1 levels and mandibular growth after the pubertal growth spurt is not fully understood. (Am J Orthod Dentofacial Orthop 2012;141:694-704)