ESPE Abstracts

Background: Subjects born small for gestational age (SGA) are at higher risk for metabolic, hormonal and reproductive problems later in life and about 2–10% of children born SGA do not catch-up in height. All these changes may influence bone mineral density (BMD).

Aim: To evaluate hormonal profile and BMD in adolescents born SGA in comparison to their peers born appropriate for gestational age (AGA).

Methods: 103 children were examined from prospective cohort followed from birth (47 SGA and 56 AGA). At the time of current examination, the mean age of children was 12.5±0.1 years, median Tanner pubertal stage 3 (2–3). Serum calcium, phosphate, parathormone (PTH), vitamin D, insulin-like growth factor 1 (IGF-1) and leptin concentrations were evaluated in all adolescents. BMD was determined by dual-energy X-ray absorptiometry (DXA) (Hologic Discovery). Fat mass percent was measured using bioelectric impedance (Jawon Medical BODYPASS X SCAN BIA). Analyses were adjusted for sex, age, pubertal stage and current BMI. Vitamin D and PTH analyses were additionally adjusted for the month of the year when blood samples were taken. Pearson correlation coefficients and hierarchical multiple regression model were used to analyze associations between BMD Z-score and perinatal and postnatal factors.

Results: There were no differences in calcium, phosphate, PTH, vitamin D, IGF-1, leptin levels and fat mass percent between SGA and AGA groups, even when SGA children with or without catch-up growth (CU+/CU−) were analyzed separately. BMD Z-score was comparable in SGA and AGA groups. However, SGA CU- children had lower BMD Z-score compared to AGA (−0.75±0.36 vs. 0.18±0.11, P=0.018). There was no significant difference in BMD Z-score in SGA CU+ compared to SGA CU- and AGA children (−0.06±0.12, P=0.071 and P=0.146, respectively). BMD Z-score correlated directly with birth length, birth weight, birth BMI (P=0.001, P=0.001 and P=0.005, respectively), height, weight and BMI standard deviation scores (SDS) up to 6 years (all P<0.05), weight gain from birth to 2 years, waist circumference, waist to height ratio, leptin concentration and fat mass percent in adolescence (P<0.001, P=0.001, P=0.024, P=0.001 and P=0.027, respectively). In the multiple regression model, birth length, birth weight, BMI at birth, BMI at 2 years of age, waist to height ratio and fat mass percent in adolescence were the most significant factors related to adolescents’ BMD Z-score (P=0.012, P=0.004, P<0.001, P=0.008, P=0.004, P<0.001, P<0.001 and P<0.001, respectively).

Conclusion: In adolescence, parameters related to BMD did not differ between SGA CU+ and AGA children. However, SGA CU- children had lower BMD Z-score compared to AGA. BMD Z-score in adolescence was directly related to size at birth, BMI at 2 years of age, waist to height ratio and fat mass percent in adolescence.