PUBERTAL GROWTH IN IDDM IS DETERMINED BY HBA(1C) LEVELS, SEX, AND BONE-AGE

OBJECTIVE -In cross-sectional studies of subjects with IDDM, the relat ionship between suboptimal pubertal growth, glycemic control, and abno rmal insulin-like growth factor I (IGF-I) levels has proved difficult to define. The objective of this study was to examine these relationsh ips in a longitudinal prospective study. RESEARCH DESIGN AND METHODS - A total of 46 children (23 boys) were measured every 3 months, and the ir bone age was assessed annually. Blood samples were obtained for HbA (1c), IGF-I, and C-peptide. Growth data were compared with national st andards, and IGF-I data were compared with a parallel longitudinal stu dy of normal schoolchildren. Data were analyzed as SD scores (mean +/- SD). RESULTS -The onset of puberty was not delayed, although in the g irls, bone age was advanced (bone age, 11.48 +/- 1.01 years vs. chrono logical age, 10.93 +/- 0.86 years [mean +/- SD]; P = 0.04). The timing of peak height velocity (PHV) was normal in both sexes, but the magni tude was reduced in girls (PHV SDS = -0.56 +/- 0.90, P < 0.02), and re ductions in height SDS between diagnosis and final height were observe d (P = 0.014). Al PHV IGF-I levels were reduced in both sexes, and the re were no sex differences in HbA(1c), levels and insulin doses. IGF-I SDS correlated with insulin dose (r = 0.47, P = 0.004) but not with P HV SDS, whereas HbA(1c) correlated negatively with PI-IV SDS in both s exes (r = -0.35, P = 0.03). In a stepwise multi pie regression analysi s, the major determinants of PHV SDS were HbA(1c), (P = 0.04), sex (P = 0.0007), and bone age (P = 0.01). CONCLUSIONS -We conclude that the magnitude of the pubertal growth spurt is related to HbA(1c) levels in both sexes, but it is reduced only in girls. This sexual dimorphism c annot be explained by differences in IGF-I levels and may relate to th e bone age advance at the onset of puberty in the girls.