Adrenal gland adaptation in response to chronic intrauterine stress on Prenatal 2D Ultrasound and Doppler: Study
Fetal growth restriction (FGR) is defined as a pathological
in utero growth disorder primarily caused by factors related to the fetus, the
mother, or the placenta. Neonatal mortality rates are higher in FGR compared to
cases in which there is normal growth. Additionally, FGR is associated with
increased risks of both short- and long-term neonatal morbidities, such as
intraventricular hemorrhage, infections, respiratory distress, delayed brain
development, impaired endocrine function, and cardiovascular disease. The
principal cause of placenta-related FGR is insufficient remodeling of the
uterine spiral arteries that supply the placenta.
The maintenance of blood supply to vital organs such as the
brain, myocardium, and adrenal glands requires redistribution of fetal
circulation, primarily through the hypothalamus-pituitary-adrenal axis (HPA).
Glucocorticoid (GC) hormones, particularly cortisol, are crucial in managing
stress responses during fetal development and in regulating the growth and
maturation of fetal tissues and organs. In contrast, studies of placental
vascular diseases associated with FGR have reported elevated plasma cortisol
levels and decreased levels of adrenocorticotropic hormone (ACTH) in affected
fetuses compared to those with normal growth.
The fetal adrenal glands, appearing early at 28–30 days
postfertilization, are among the largest organs when the fetus is near term.
The fetal adrenal cortex undergoes rapid growth during the prenatal period and
divides into three zones: the fetal zone (FZ), the definitive zone (DZ), and
the transitional zone (TZ). The fetal adrenal medulla, however, is not recognizable
until delivery. The FZ is responsible for the synthesis of
dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEA-S),
which are crucial for facilitating placental estrogen production. Meanwhile,
the DZ and TZ, also known as the “neocortex,” are involved in the production of
cortisol and aldosterone during pregnancy.
The fetal adrenal glands comprise a highly vascularized
organ, which receives blood from several primary arteries: the superior adrenal
artery (SAA), middle adrenal artery (MAA), and inferior adrenal artery (IAA),
which originate from the inferior phrenic artery, abdominal aorta, and renal artery,
respectively. The superior and inferior portions of the DZ are primarily
supplied by the SAA and IAA, respectively, while the FZ is predominantly
supplied by the MAA. Theoretically, chronic fetal hypoxia and stress could
trigger the activation of the HPA axis, potentially affecting both the adrenal
vessels and the adrenal glands. The aim of this study was to compare the
differences in Doppler indices of the adrenal artery and adrenal gland sizes
between fetuses with growth restriction and those with normal growth.
A multicenter, cross-sectional study was conducted from
February to December 2023. Authors compared 34 FGR to 34 with normal growth in
terms of inferior adrenal artery (IAA) Doppler indices and adrenal gland
volumes.
The IAA peak systolic velocity (PSV) in the FGR group was 14
9±2 9 cm/s compared to 13 5±2 0 cm/s in the normal group, with a mean
difference of 1.4 cm/s (95% confidence interval [CI]: 0.27–2.65; p value =
0.017).
There were no significant differences between groups in
terms of IAA pulsatility index (PI), resistance index (RI), or
systolic/diastolic (S/D), with p values of 0.438, 0.441, and 0.658,
respectively. The volumes of the corrected whole adrenal gland and the
corrected neocortex were significantly larger in the FGR group, with p values
of 0.031 and 0.020, respectively.
The Doppler study of the IAA in fetuses with growth
restriction revealed a significant increase in PSV, while no changes were
observed in the PI, RI, and S/D compared to those with normal growth.
Additionally, both the corrected WAG volume and the corrected neocortex volume
were significantly enlarged in FGR.
Both increased IAA PSV and enlarged volumes of the corrected
WAG and neocortex were found in fetuses with FGR, suggesting significant
adrenal gland adaptation in response to chronic intrauterine stress.
Source: Suphawan Pattamathamakul,1 Chatuporn Duangkum , 1
Sukanya Chaiyarach; Wiley Journal of Pregnancy Volume 2024, Article ID 9968509,
10 pages https://doi.org/10.1155/2024/9968509
