ESPE Abstracts

Background: P450 oxidoreductase (POR) is a co-factor critical for the function of type 2 microsomal cytochrome P450 enzymes. POR deficiency (PORD) results in a rare form of congenital adrenal hyperplasia, with combined attenuation of CYP21A2 and CYP17A1 steroidogenic enzymes. It is characterised by combined deficiencies of glucocorticoids and androgens postnatally. Differences in sex development can arise in both sexes due to antenatal activation of the alternative androgen pathway in affected females. Associated skeletal malformations are commonly observed. Early diagnosis is critical for optimal management. The mature urinary steroid metabolome for PORD is well described. However, newborn urine steroid metabolome is distinct due to fetoplacental and maternal contributions, involution of the foetal adrenal structure, and unique neonatal steroid metabolism. Here, we describe the urinary steroid excretion in the first week of life in three infants affected with PORD.

Methods: Case 1 and 2 were two affected siblings born three years apart who were stillborn and first-day deceased, respectively. DNA sequencing revealed a homozygous 3 bp deletion in exon 6 leading to an glutamic acid deletion (p.Glu217del). Bladder contents were obtained from case 1, and excreted urine was obtained from the case 2. Case 3, from a second family, was antenatally diagnosed carrying a homozygous p.Ala287Pro mutation. Urine was collected from the baby daily during the first week of life. Urinary steroid metabolome analysis was performed by gas chromatography-mass spectrometry.

Results: The day 1 urinary steroid metabolome for our affected infants was distinct. We observed very high concentrations of unmetabolized corticosterone. The major abundant newborn metabolites, estriol (a primary fetoplacental unit product) and 16α-hydroxylated metabolites of Δ⁵ steroids DHEA and pregnenolone, were absent due to attenuation of CYP19A1, CYP17A1 and CYP3A7. Serial measurements over the first week of life revealed a rapidly changing metabolome, with the emergence of pregnenediol (5PD, pregnenolone metabolite), a classical marker of PORD, as a dominant metabolite by day 7 of life.

Discussion: Our findings suggest that PORD can be reliably biochemically confirmed from day 7 of life using previously described urinary metabolite ratios. Prior to this, standard diagnostic ratios are compromised. Our results suggest earlier diagnosis can be established by the absence of key dominant neonatal metabolites accompanied by the vast excretion of corticosterone. We propose additional diagnostic ratios of 16αOH pregnenolone to pregnenediol, corticosterone to cortisol and corticosterone to its reduced excretory metabolites, illustrating characteristic metabolic alterations in newborns.