Histological and Histochemical Analysis of Foetal Suprarenal Gland Maturation from 13-40 Weeks of Gestation: An Observational Study

Introduction: The Suprarenal Glands (SRG), a pair of endocrine glands located at the upper poles of the kidneys, originate from different developmental origins. The glands are divided into an outer cortex and an inner medulla. The cortex is further divided into the Zona Glomerulosa (ZG), Zona Fasciculata (ZF) and Zona Reticularis (ZR) while the medulla contains chromaffin cells— specialised neuroendocrine cells that synthesise and secrete catecholamines such as epinephrine and norepinephrine. These cells are also being studied for their regenerative applications in treating neurodegenerative diseases, including Parkinson’s disease. Aim: To identify the histological features of the foetal suprarenal cortex and medulla, track changes during development and measure the number of chromaffin cells at various developmental stages. Materials and Methods: This observational study was conducted from February 2024 to January 2025 in the Department of Anatomy, SRM Medical College Hospital and Research Centre, Chennai, Tamil Nadu, India. Thirty-two foetuses of gestational ages 13–40 weeks were collected. The gestational age of the foetuses was estimated by Crown–Rump Length (CRL) and they were grouped into four groups (I–IV). The tissues from each sample were collected, processed and sectioned for histology and histochemical procedures. Images of the sections were captured with an inverted microscope attached to a CCD camera and these images were analysed using ImageJ software. The parameters measured included the thickness of the ZG, ZF, ZR and the medulla and the number of chromaffin cells. Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) version 25.0. Results: The cortex becomes progressively thinner with increasing gestational age. The medulla, on the other hand, shows an increase in thickness beginning around the late second trimester and reaches its maximum by the late third trimester. The right SRG showed a gradual increase in chromaffin cells up to the late second trimester, with around a 30–35% decrease in the early third trimester. The left gland showed a gradual increase in chromaffin cells from the early second trimester, reaching around a 50% increase by the late third trimester. Conclusion: The findings suggest functional and developmental asymmetries between the foetal SRGs, with the left gland undergoing more significant changes compared to the right. This asymmetry may have implications for understanding foetal stress responses and the maturation of neuroendocrine regulation.