Comparison of leptin levels, body composition and insulin sensitivity and secretion by OGTT in healthy, early pubertal girls born at either appropriate- or small-for-gestational age.

BACKGROUND: Small for gestational age (SGA) has been associated with decreased insulin sensitivity (IS). A possible mechanism is the postnatal development of a metabolically disadvantageous body composition (BC). AIM: To determine whether there are differences between IS and BC in girls in early puberty who were SGA (birth weight < 10th percentile) or appropriate for gestational age (AGA, 10th-90th percentile). METHODS: Age-matched (SGA/AGA) early pubertal girls (Tanner II) were recruited from local schools. We determined waist circumference (WC), the sum of four skinfolds (S4S), and per cent fat mass (fat %) by impedanciometry. Leptin and OGTT assays were performed. The insulinogenic index (I-In), HOMA-IR (homeostasis model assessment of insulin resistance) and WBISI (whole body insulin sensitivity) were calculated. RESULTS: Median age (interquartile range) for 30 SGA and 35 AGA girls was 10.2 (1.1) vs. 9.8 (0.9), respectively (P = NS). BMI percentiles were 62.6 (56) vs. 67.4 (39); WC 60.5 (9.5) vs. 62.2 (6.5) cm; S4S 52 (30) vs. 52.2 (29.5) cm, and fat %[26.2 (6.7) vs. 28.5 (6.3)] was similar in both groups. SGA girls had higher leptin levels [15.4 (9.7) vs. 9.6 (11) ng/ml; P = 0.01] and I-In [2.05 (1.86) vs. 1.47 (1.27) microU/ml* mg/dl; P = 0.02]. No differences between HOMA-IR [2.07 (1.26) vs. 2.04 (1.4)] and WBISI [5.3 (3.3) vs. 5.1 (3.1)] were found between groups. CONCLUSION: The higher leptin level and I-In in girls born SGA at the beginning of puberty may be early indicators of an underlying subtle degree of insulin resistance, despite similar BMI and BC to AGA girls.