Context: Estrogens and androgens play key roles for pubertal onset and sexual maturation. Most currently used immunoassays are not sensitive enough to accurately measure the low circulating levels of sex steroids in children without any signs of puberty. However, this does not exclude that sex steroids have important biological roles in prepubertal children.
Objectives: To accurately determine levels of sex steroid hormones and their metabolites in serum of healthy children before any physical signs of puberty and to evaluate possible sex differences.
Main outcome measures: Total (unconjugated plus conjugated) serum levels of 17beta-testosterone, 17alpha-testosterone, 5alpha-dihydrotestosterone, 5beta-dihydrotestosterone, androsterone, etiocholanolone, estradiol, and estrone measured by an ultrasensitive method based on gas chromatography-tandem mass spectrometry in samples from 81 healthy schoolchildren (42 boys) without any signs of puberty. For comparison, 48 pubertal children were studied.
Results: 17beta-Estradiol levels in prepubertal boys were undetectable or extremely low (median < 3.7 pmol/liter), whereas levels in prepubertal girls were significantly higher (median 9.6 pmol/liter, P < 0.001). Among the older prepubertal children (>8 yr), girls had significantly higher androsterone (4.07 vs. 1.45 nmol/liter, P < 0.05), etiocholanolone (5.45 vs. 1.95 nmol/liter, P < 0.0001), 5alpha-dihydrotestosterone (0.11 vs. <0.10 nmol/liter, P < 0.01), and 17beta-testosterone concentrations (0.69 vs. 0.47 nmol/liter, P < 0.05) compared with similarly aged prepubertal boys.
Conclusion: Using an accurate and sensitive method, we found significantly higher levels of estrogens as well as androgen metabolites in prepubertal girls compared with age-matched boys. The higher prepubertal sex steroid levels in girls may contribute to their earlier onset of puberty including pubic hair development.