Parturition itself is the basis for fetal adrenal involution.

Context: Newborn infants show a postnatal decline in androgen levels as the fetal adrenal glands involute.

Hypothesis: Placental factors up-regulate dehydroepiandrosterone sulfate (DHEA-S) generation. Hence, regardless of age, parturition will result in fetal adrenal involution and decline in DHEA-S levels.

Subjects And Methods: Premature neonates (n = 30) with gestational age 26-35 wk were studied. Adrenal volume by ultrasonography and serum DHEA-S, cortisol, and androstendione levels were followed weekly between d 1 and 28 of life.

Results: Serum DHEA-S was high on d 1 of life, declining rapidly regardless of gestational age during the first week of life (P < 0.001), and serum androstenedione and cortisol levels followed a similar pattern. Androstenedione levels showed a rise as of d 21 of life in boys but not in girls. The adrenals decreased in ultrasonographic volume from d 1 to 14 of life (P < 0.001), regardless of gestational age.

Conclusions: Involution of the adrenal is faster than previously reported and, regardless of gestational age, occurs within the first week of life in terms of hormone secretion and within 2 wk in adrenal size. Involution involves a decline in DHEA-S but also in androstenedione and cortisol secretion, with a change in enzymatic activity. Males and females differ in their androstenedione levels and enzymatic activity. Parturition itself is the basis for fetal adrenal involution, supporting a key role for placental factors in maintaining the fetal adrenal and generating adrenal androgens.