Pituitary gland shrinkage in bipolar disorder : the role of gender

Background: Hyperactivity of the Hypothalamic-Pituitary-Adrenal Axis (HPAA) has been consistently reported in mood disorders. However, only few studies investigated the Pituitary gland (PG) in Bipolar Disorder (BD) and the results are so far contrasting. Therefore, the aim of this study is to explore the integrity of the PG as well as the role of gender and the impact of clinical measurements on this structure in a sample of BD patients compared to healthy controls (HC). Methods: 34 BD patients and 41 HC underwent a 1.5 T MRI scan. PG volumes were manually traced for all subjects. Psychiatric symptoms were assessed by means of the Brief Psychiatry Rating Scale, the Hamilton Depression Rating Scale and the Bech Rafaelsen Mania Rating Scale. Results: We found decreased PG volumes in BD patients compared to HC (F = 24.9, p < 0.001). Interestingly, after dividing the sample by gender, a significant PG volume decrease was detected only in female BD patients compared to female HC (F = 9.1, p < 0.001), but not in male BD compared to male HC (F = −0.12, p = 0.074). No significant correlations were observed between PG volumes and clinical variables. Conclusions: Our findings suggest that BD patients have decreased PG volumes, probably due to the long-term hyperactivity of the HPAA and to the consequent strengthening of the negative feedback control towards the PG volume itself. This alteration was particularly evident in females, suggesting a role of gender in affecting PG volumes in BD. Finally, the absence of significant correlations between PG volumes and clinical variables further supports that PG disruption is a trait feature of BD, being independent of symptoms severity and duration of treatment.