Imaging the pituitary in psychopathologies: a review of in vivo magnetic resonance imaging studies

The pituitary gland (PG) is a key component of the essential endocrine systems in humans and animals, including the hypothalamic-pituitary-adrenal, hypothalamic-pituitary-gonadal, and hypothalamic-pituitary-thyroid axes. Structural changes in the PG are observed in a number of psychiatric disorders. Psychiatric disorders are typically characterized by subtle, time-dependent anatomical changes in the brain, and their study necessitates highly powered, longitudinal investigations. Structural magnetic resonance imaging (MRI) is a non-invasive technology that is ideally suited to detect changes in anatomical structures over time. In this paper, we will review the main findings on pituitary function and structure in the context of healthy development and of psychiatric disorders, with particular emphasis on MRI studies. The latter have not always succeeded in providing a clear theoretical framework of mental disorders, which may be explained by low resolution and differences in preprocessing methods, imprecise segmentation rules that do not account for the anatomical and functional specificity of the anterior and posterior lobes of the PG, and inadequate categorization of clinical subjects. We review those limitations and propose solutions for future research.