The relation between the lack of the posterior pituitary bright signal on magnetic resonance images and posterior pituitary hormone in elderly subjects

Abstract The aim of this study was to clarify the morphological characteristics of the pituitary gland, especially posterior pituitary, by magnetic resonance imaging (MRI) in elderly subjects and to relate them to pituitary hormone secretion. We investigated the pituitary MRI in 99 aged (33 males, 66 females; median 82 y) and 41 young (13 males, 28 females; median 34 y) healthy subjects. Pituitary height, width and volume in the elderly subjects were less than those in the young subjects. Empty sella was more frequently observed in the elderly subjects (18%), especially women, than in the young ones. Posterior pituitary bright signal (PBS) on T1-weighted MRI was not detected in 30% of the elderly subjects, while it could be detected in all the young subjects. None of the elderly subjects showed clinical signs or symptoms of diabetes insipidus. Fasting plasma osmolality and AVP in the elderly subjects were significantly higher than those in the young subjects. Moreover, plasma AVP was significantly higher in the elderly subjects without the PBS than in those with the PBS. It is suggested that the excessive release of AVP from posterior pituitary by the continuation of plasma high osmolality in the elderly subjects may lead to depletion of the neurosecretory granules in the posterior pituitary gland and may result in disappearance of the PBS on T1-weighted MRI. These morphological changes might relate to the normal physiological occurrence of aging.