Endocrine Abstracts

JOINT2122

Context: Age at puberty has declined concomitant with a tendency to become taller. This paradox – becoming taller despite diminished total growth period – may rely on faster linear growth during childhood and puberty in boys, which has previously been shown for girls.

Objective: Growth velocity, skinfold thickness (SFT), IGF-I and fasting insulin levels in relation to pubertal timing; A) early: below median age for testicular volume enlargement (TV) >3 ml and B) late pubertal onset (above the median age) in healthy boys.

Design and setting: Longitudinal study with biannual assessment of TV, SFT, growth velocity, IGF-I and fasting insulin levels. Peak height velocity (PHV) was determined by a statistical model.

Participants: 105 boys (947 examinations) at a median of 9.0 years at first examination. Age at pubertal onset was available in 62 boys.

Results: Early maturing boys had significantly higher growth velocity (mean δ 0.45 (0.17 – 0.72) cm/yr; P < 0.001) compared with late maturing boys evaluated over the peri-pubertal period (-/+ 3 years before/after pubertal onset). However, the late maturing boys were taller than the early maturing boys (mean δ 6.4 (1.0 – 11.8) cm; P = 0.023) 3 years after pubertal onset. IGF-I and fasting insulin levels were similar between early and late maturing boys when evaluated in relation to age at pubertal onset. Independent of puberty, the changes in IGF-I were associated with the changes in height (P < 0.001) evaluated over the first 2 years after pubertal onset.

Conclusion: Early maturation was associated with increased growth velocity and PHV. However, it was not sufficient to compensate for the shorter total growth period, as seen for girls. Changes in IGF-I were related to growth but were independent of pubertal timing.