Natural History of Idiopathic Advanced Bone Age Diagnosed in Childhood: Pattern of Growth and Puberty

Background: Significant idiopathic bone age (BA) advancement is defined as BA >2 SD above the mean chronological age (CA) with no underlying etiology. BA advancement due to endocrinopathies is associated with early puberty and compromised adult height (AHt), necessitating treatment. The natural history of idiopathic BA advancement is not well-established. Aim: To determine the pattern of growth and puberty, and validity of AHt prediction in idiopathic BA advancement. Methods: Fifty-five prepubertal patients (20 boys aged 6.7 +/- 2.2 years, 35 girls aged 6.4 +/- 2.0 years) evaluated between 1985 and 2008 were found to have idiopathic BA advancement. Assessed during follow-up were: BA, height (Ht), weight (Wt), pubertal course and predicted AHt (PAHt). Attained AHt was compared to PAHt and to mid-parental Ht (MPHt). Results: Throughout follow-up, BA-SDS (SD score) significantly declined (p < 0.001), Ht-SDS significantly decreased (p = 0.006) and Wt-SDS did not change. Pubertal onset, duration and growth were within the normal range. Attained AHts did not differ significantly from MPHts (boys: 172 +/- 6.7 vs. 171 +/- 6.1 cm; girls: 160.5 +/- 6.5 vs. 159.0 +/- 6.8 cm). PAHts using the 'accelerated' tables of Bayley and Pinneau were accurate. Conclusion: Idiopathic BA advancement differs from BA advancement with underlying endocrinopathy in evolution of BA progression (decline in BA-SDS), growth pattern, validity of AHt prediction and uncompromised AHt. This indicates that it requires minimal clinical monitoring and usually does not mandate treatment. Copyright (C) 2010 S. Karger AG, Basel