Perimenopausal hormone therapy is associated with regional sparing of the CA1 subfield: a HUNT MRI study
Abstract
Observational studies support a neuroprotective role of hormone therapy (HT) in the perimenopause,
with hippocampal size being a widely used biomarker.We investigated the effect of HT started before the
onset of menopause and lasting for at least 3 years on hippocampal volume and shape in 80 postmenopausal
women and 80 controls matched on age and intracranial volume taken from a large
community-based sample (Nord-Trøndelag Health Studyemagnetic resonance imaging). The main effect
of hormone group showed a statistically significant difference in hippocampal volumes (p ¼ 0.028). Both
the right (3.2%) and left (2.8%) hippocampal volumes were larger in the HT group but only significant for
the right hippocampus (p ¼ 0.023). Shape analysis revealed significant regional sparing of the medial
aspect of the right hippocampal head and lateral aspect of the body extending to the tail, corresponding
to the cornu ammonis, including part of the subiculum, in the HT group. A similar nonsignificant pattern
was observed in the left hippocampus. The present study provides support for the critical window theory
demonstrating that HT initiated in the perimenopause has neuroprotective properties.