Abstract
Introduction Oestrogen has a protective effect against neurodegenerative conditions, including glaucoma and dementia. Animal models suggest that oestrogen has a vasodilatory effect, which is a possible mechanism for this. However, the full influence of oestrogen on specific cerebrovascular functions is unclear.
Aims This study aims to investigate the influence of hormonal fluctuations across a healthy menstrual cycle on measures of retinal and cortical vascular functioning.
Methods 27 menstruating participants (age mean[SD]=22.94[3.52] years) completed a testing session during the early-follicular, late-follicular, and mid-luteal phase of their menstrual cycle. Bloods were taken to measure circulating hormones.
Retinal vasculature was assessed using a Swept-Source OCT (TOPCON healthcare), including:
Choroidal thickness – 6mm2 OCT scan
Vessel density, radius, and resistance – 3mm2 OCT Angiography
Cortical data were acquired on a Siemens MAGNETOM Prisma 3T MRI scanner and include:
Grey matter Cerebral Blood Flow (CBF) and Arterial Arrival Time (AAT) – MPLD-pCASL scan
Global Oxygen Extraction Fraction (OEF) – TRUST sequence
Linear models investigated the amount of variance explained by circulating oestradiol.
Results Oestradiol significantly decreased retinal resistance (χ2(1)=6.1218, P=0.01335), an effect which was greatest in the foveal vessels. Other retinal measures were stable across the menstrual cycle. No association was found with OEF, but oestradiol did significantly increase CBF (χ2(1)=17.801; P=2.452e-5) and AAT (χ2(1)=9.5183; P=0.002034), which was a global effect.
Conclusion Evidence for oestrogen’s vasodilatory influence was demonstrated across a menstrual cycle and in multiple vascular beds. This provides information into how oestrogen influences the cerebrovascular system and highlights possible mechanisms by which oestrogen has a protective effect against neurodegenerative conditions.
Acknowledgements The Wellcome Trust (WT224267)
