Increased signal on T1-weighted images of the residual normal anterior pituitary gland following medical treatment of pituitary prolactinoma

Purpose. To illustrate that residual normal pituitary gland may show hyperi ntense signal on T1-weighted image after medical treatment of pituitary pro lactinoma. Material and methods. Three patients treated with bromocriptine for a prola ctinoma and showing hyperintense signal of the residual normal pituitary ti ssue on T1-weighted images were studied. In all patients, measurements of t he anterior pituitary gland signal (APGS) and the temporal lobe white matte r signal (TLWMS) were obtained by a "region of interest" (ROI) on coronal T 1-weighted images. The APGS/TLWMS ratios were calculated and compared to th ose of a control group of 30 normal subjects. Results. In the three patients, the measurements obtained by ROI confirmed the visual impression of high signal of the residual normal pituitary tissu e. Ratios were ranging from 1.15 to 1.21, while they were ranging, in the c ontrol group from 0.92 to 1.09. Conclusion. In patients with prolactin-secreting adenoma seen after medical treatment, high signal of the residual normal pituitary tissue can be obse rved, probably due to cellular hyperactivity as it can be noticed during so me physiological states. This pattern has to be differentiated from other p ituitary abnormalities demonstrating T1 hyperintensity such as hemorrhagic changes of a prolactinoma.