Pituitary volume in psychosis: the first review of the evidence.

The pituitary gland regulates hypothalamic-pituitary-adrenal (HPA) axis activity by secreting adrenocorticotropic hormone (ACTH), and HPA axis abnormalities have been described in psychosis. Moreover, the pituitary gland secretes prolactin, and some antipsychotics increase the secretion of this hormone. Therefore, it is possible that psychosis is associated with an abnormal volume of the pituitary, as a consequence of a dysfunction in either or both these hormonal systems. The present review of the studies conducted so far clearly indicates that the pituitary is a dynamic organ, which changes differently at different stages of the psychotic disorder, in response to both the disorder itself and the treatment with antipsychotics. Specifically, the pituitary is larger in the months immediately preceding or following the psychosis onset, independently from antipsychotic treatments. However, following this initial enlargement, the pituitary tends to become smaller, as suggested by studies in patients with psychosis of at least two years of duration. On top of these dynamic changes that are linked to the course of the disorder, antipsychotics, and especially antipsychotics inducing hyperprolactinaemia, exert additional enlarging effects on pituitary volume. We suggest that the increased pituitary volume associated with the development of psychosis is due to activation of the hormonal stress response and, specifically, to an increase in the size and number of corticotroph cells producing ACTH, while the increased pituitary volume induced by antipsychotics is linked to the stimulating effects of these drugs on lactotroph cells producing prolactin. Future studies should address these issues that are relevant in improving the care of patients with psychosis.