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Open access

Britt J van Keulen, Michelle Romijn, Bibian van der Voorn, Marita de Waard, Michaela F. Hartmann, Johannes B. van Goudoever, Stefan A. Wudy, Joost Rotteveel, and Martijn J.j. Finken

Objective

Sex-specific differences in hypothalamic-pituitary-adrenal axis activity might explain why male preterm infants are at higher risk of neonatal mortality and morbidity than their female counterparts. We examined whether male and female preterm infants differed in cortisol production and metabolism at 10 days post-partum.

Design and methods

This prospective study included 36 preterm born infants (18 boys) with a very low birth weight (VLBW) (<1.500 gram). At 10 days postnatal age, urine was collected over a 4- to 6-hr period. Glucocorticoid metabolites were measured using gas chromatography-mass spectrometry. Main outcome measures were: (1) cortisol excretion rate, (2) sum of all glucocorticoid metabolites, as an index of corticosteroid excretion rate, and (3) ratio of 11-OH/11-OXO metabolites, as an estimate of 11β-hydroxysteroid dehydrogenase (11β-HSD) activity. Differences between sexes, including interaction with Score of Neonatal Acute Physiology Perinatal Extension-II (SNAPPE II), sepsis and bronchopulmonary dysplasia (BPD), were assessed.

Results

No differences between sexes were found for cortisol excretion rate, corticosteroid excretion rate or 11β-HSD activity. Interaction was observed between: sex and SNAPPE II score on 11β-HSD activity (p=0.04) and sex and BPD on cortisol excretion rate (p=0.04).

Conclusion

This study did not provide evidence for sex-specific differences in adrenocortical function in preterm VLBW infants on a group level. However, in an interaction model sex differences became manifest under stressful circumstances. These patterns might provide clues for the male disadvantage in neonatal mortality and morbidity following preterm birth. However, due to the small sample size, the data should be seen as hypothesis generating.

Open access

Britt J van Keulen, Conor V Dolan, Bibian van der Voorn, Ruth Andrew, Brian R Walker, Hilleke Hulshoff Pol, Dorret I Boomsma, Joost Rotteveel, and Martijn J J Finken

Objective

Sex differences in disease susceptibility might be explained by sexual dimorphism in hypothalamic-pituitary-adrenal axis activity, which has been postulated to emerge during puberty. However, studies conducted thus far lacked an assessment of Tanner pubertal stage. This study aimed to assess the contribution of pubertal development to sexual dimorphism in cortisol production and metabolism.

Methods

Participants (n = 218) were enrolled from a population-based Netherlands Twin Register. At the ages of 9, 12 and 17 years, Tanner pubertal stage was assessed and early morning urine samples were collected. Cortisol metabolites were measured with GC-MS/MS and ratios were calculated, representing cortisol metabolism enzyme activities, such as A-ring reductases, 11β-HSDs and CYP3A4. Cortisol production and metabolism parameters were compared between sexes for pre-pubertal (Tanner stage 1), early pubertal (Tanner stage 2–3) and late-pubertal (Tanner stage 4–5) stages.

Results

Cortisol metabolite excretion rate decreased with pubertal maturation in both sexes, but did not significantly differ between sexes at any pubertal stage, although in girls a considerable decrease was observed between early and late-pubertal stage (P < 0.001). A-ring reductase activity was similar between sexes at pre- and early pubertal stages and was lower in girls than in boys at late-pubertal stage. Activities of 11β-HSDs were similar between sexes at pre-pubertal stage and favored cortisone in girls at early and late-pubertal stages. Cytochrome P450 3A4 activity did not differ between sexes.

Conclusions

Prepubertally, sexes were similar in cortisol parameters. During puberty, as compared to boys, in girls the activities of A-ring reductases declined and the balance between 11β-HSDs progressively favored cortisone. In addition, girls showed a considerable decrease in cortisol metabolite excretion rate between early and late-pubertal stages. Our findings suggest that the sexual dimorphism in cortisol may either be explained by rising concentrations of sex steroids or by puberty-induced changes in body composition.