ESPE Abstracts (2018) 89 P-P2-303

Foot Length Growth is a Novel Marker of Early Puberty

Ben Balzera,b, Hoi Lun Chengb, Frances Gardenc,d, Georgina Luscombea, Karen Paxtona, Catherine Hawkea, David Handelsmane & Katharine Steinbecka,b

aUniversity of Sydney, Sydney, Australia; bThe Children’s Hospital at Westmead, Sydney, Australia; cUniversity of New South Wales, Sydney, Australia; dIngham Institute of Applied Medical Research, Liverpool, Australia; eANZAC Research Institute, Sydney, Australia

Introduction: Pubertal growth is hormone dependent. The anthropometric (height, weight) and sexual (Tanner stage (TS)) changes are accompanied by growth in foot length. However, the relationship between changes in foot length and other anthropometry remains unclear. Our aim was to determine how changes in foot length relate to growth parameters (height and weight), self-rated TS and serum sex steroids.

Methods: We used data from the Adolescent Rural Cohort study of Hormones, health, Education, environments and Relationships (ARCHER); a community sample of adolescents (aged 9–14 y at baseline) who were followed for three years. Annual data collection included: anthropometry (height, weight, foot length), self-rated TS, date of menarche and blood samples. Blood was analysed using LC-MS/MS for oestradiol (E2), testosterone (T) and dehydroepiandrostenedione (DHEA). Insulin-like growth factor 1 (IGF1) was measured via radioimmunoassay. Pre-puberty was defined by baseline T <0.5 nmol/l for males or E2 <40 pmol/l for females.

Results: Data were available for 293 subjects. 13% (17/128) of females and 43% (71/165) of males were pre-pubertal at baseline. In the three years from baseline to final follow-up, both sexes showed expected increases in anthropometry, TS and most serum hormones. Average annual % increase in foot length was greater for adolescents classified as pre-pubertal compared to pubertal (F:2.7% vs 1.5% P<0.001; M:4.2% vs 2.9%, P<0.001). Increased foot length was associated with increases in height, weight and TS (all P<0.05; β (95% CI) Height: F:5.78 cm (5.32–6.23), M:6.71 cm (6.50–6.93), Weight: F:6.64 kg (5.93–7.35), M:6.20 kg (5.87–6.53), TS: F:0.50 (0.42–0.59), M:0.54 (0.50–0.59)). In males, increases in T, E2, and IGF-1, respectively, were associated with increases in foot length (all P<0.05; T 0.18 cm (0.16–0.20), E2 0.017 cm (0.012–0.022), IGF1 0.03 cm (0.02–0.04). In females, increases in T, E2 and IGF-1 in pre-menarcheal girls were associated with increased foot length (all P<0.05; T:0.74 cm (0.09–1.4), E2:0.004 cm (0.001–0.006), IGF1:0.03 cm (0.01–0.05)) but not post-menarcheal girls.

Discussion: We provide the first longitudinal evidence that foot length is related to conventional pubertal changes in physical characteristics and serum sex steroids using highly accurate LC-MS/MS methodologies, with more foot growth in pre-pubertal adolescents. Change in foot length is a novel, cost-effective and easily demonstrable marker of early pubertal changes, something of utility to adolescents, parents and clinicians alike. We postulate that early foot growth provides a physical base to support the future pubertal growth spurt.

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