ESPE Abstracts

Background: Gender differences in sex steroids and IGF1 are well known from pubertal years into adulthood. Few studies report data from pre-school years.

Objective and hypotheses: To study gender specific changes in sex steroids and IGF1 at birth and at 5 years of age and correlate these with auxological measurements. There are gender differences in IGF1 levels due to differences in sex steroids already at birth and during pre-school years.

Method: Eighty prepubertal children (35 females and 45 males) born moderately preterm (gestational age 32–37 weeks) were examined with blood sampling and auxological measurements at birth and 5 years of age. Estradiol, testosterone, and IGF1 were measured with RIAs.

Results: At birth, IGF1 levels for boys were significantly lower; median (range) 38 (7–93) μg/l than for girls 54 (8–96) μg/l, P<0.05. Testosterone levels were higher for boys 3.8 (1.7–8.8) vs 3.0 (1.2–5.1) nmol/l for girls, P<0.01. There was no statistical difference in gestational age; boys 35.8 (33.0–36.9) weeks vs girls 35.6 (32.0–36.7) weeks, nor in birth weight or birth length. At 5 years of age, boys still had lower IGF1 levels; 89 (45–177) vs 105 (45–221) μg/l in girls, P<0.01. Testosterone levels were significantly lower in boys; 0.14 (<0.03–0.34) vs 0.20 (<0.03–0.36) nmol/l in girls, P<0.05.

Conclusion: Gender differences in testosterone and IGF1 were found both at birth and at 5 years of age. Boys had lower levels of IGF1 at both time points. However, there was a shift in gender differences concerning testosterone with higher levels at birth and lower levels at 5 years in boys. The higher testosterone levels seen in girls at 5 years of age may be due to a non-detected earlier adrenarche in girls.