Background Liquid chromatography/mass spectrometry/mass spectrometry (LCMSMS) is useful for analyzing neonatal serum levels of steroid hormones because more than 10 steroid hormones can be simultaneously analyzed in only 100 μl of serum, and it has a high sensitivity and does not cross-react with other fetal steroid hormones. Herein, we devised normative standards of term neonatal steroid hormones using LCMSMS.

Objective We assessed neonatal adrenal function by analyzing serum steroid hormones using LCMSMS, and compared the differences in gestational age and birth weight.

Method A total of 164 neonates without endocrinological abnormalities were enrolled. Ninety-nine were term appropriate for gestational age (term AGA). Twenty were term small for gestational age (term SGA). Twenty-eight were 34–36 week gestation AGA (preterm AGA). Seventeen were 34–36 week gestation SGA (preterm SGA). We measured cortisol, DHEA, and 17OH pregnenolone (17OHP5) (ng/ml) with LCMSMS using 100 μl of serum 3–6 days after birth. The Mann–Whitney U test was used for statistical analysis.

Results Cortisol was significantly lower in term SGA than in term AGA. DHEA and 17OHP5 were significantly lower in term AGA than in preterm AGA, and in term SGA than in preterm SGA. Additionally, 17OHP was significantly lower in term SGA than in term AGA.

Conclusion Basal cortisol secretion from the permanent adrenal cortex and 17OHP5 secretion from the fetal cortex was low in term SGA. The volume of the permanent adrenal and fetal cortexes in term SGA is small to account for the reduced systemic growth.