Hippocampal to pituitary volume ratio: A specific measure of reciprocal neuroendocrine alterations in alcohol dependence

Objective: Studies to date provide conflicting views of the relationship between corticosteroids and decreased hippocampal volume in alcoholism. If this were mediated through the hypothalamic-pituituy-adrenal (HPA) axis, enlarged pituitary volumes relative to hippocampal volumes might be expected and be measurable using the hippocampus to pituitary volume (H:P) ratio. Method: Using magnetic resonance imaging (MRI), we performed volumetric analysis of the pituitary and hippocampus on 10 subjects with alcohol dependence (AD) and on 10 normal control subjects. Results: Compared to normal controls, AD subjects demonstrated a trend towards decreased hippocampal volume (p < .06) and increased pituitary volume (p < .07). More importantly,H:P ratios were significantly smaller in AD subjects (P < .01). This observation persisted even when covaried for age. Conclusions: Reduced H:P ratio fits the hypothesis that ethanol stimulates pituitary corticotrophs resulting in elevated corticosteroid levels and possible injury to this hippocampus. If replicated, reduced H:P ratio may serve as a clinical measure of reciprocal neuroendocrine changes in chronic heavy ethanol use.