Decreased pituitary volume in patients with bipolar disorder

Background: Neuroendocrinologic investigations in bipolar disorder have sug gested abnormalities in pituitary function. However, few imaging studies ha ve evaluated possible anatomical differences in this brain structure in moo d disorder patients. Our aim was to examine potential abnormalities in pitu itary volume in patients with bipolar and in a comparison group of patients with unipolar disorder. Methods: We measured the volumes of the pituitary gland in 23 patients with bipolar disorder (mean +/- s.d. = 34.3 +/- 9.9 years) and 13 patients with unipolar disorder (41.2 +/- 9.6 years), and 34 healthy control subjects (3 6.6 9.6 years) using 1.5 mm thick TI-weighted coronal 1.5 T MRI images. All measurements were done blindly by a trained rater. Results: Patients with bipolar disorder had significantly smaller pituitary volumes than healthy control subjects (mean volume +/- s.d. = 0.55 +/- 0.1 5 ml and 0.68 +/- 0.20 ml, respectively; ANCOVA, F = 8.66, p 0.005), and th an patients with unipolar disorder (0.70 +/- 0.12 ml, F = 5.98, p = 0.02). No differences were found between patients with unipolar disorder and healt hy control subjects (F = 0.01, p = 0.91). Conclusions: To our knowledge, this is the first study that reports smaller pituitary volumes in bipolar disorder. Our findings suggest that detectabl e abnormalities in pituitary size are present in patients with bipolar diso rder, which may reflect a dysfunctional HPA avis. (C) 2001 Society of Biolo gical Psychiatry.