General description

Lymphocytic hypophysitis (LYH) is a chronic inflammatory condition characterized by the infiltration of lymphocytes and plasma cells, involving T and B cells, into the pituitary gland and hypothalamus. This infiltration leads to pituitary insufficiency.

Clinically, patients with LYH often present with symptoms including headaches, visual field disturbances, and hyperprolactinemia. Additionally, manifestations such as hypopituitarism and central diabetes insipidus are commonly observed.

Radiographic features

Differentiating lymphocytic hypophysitis (LYH) from pituitary adenoma can indeed be challenging due to overlapping imaging features. In LYH, a common finding is the loss of the characteristic T1WI high signal in the posterior pituitary. Additionally, pituitary enlargement is a frequent feature of LYH; however, this enlargement tends to be more symmetrical compared to the often asymmetrical enlargement seen in pituitary adenomas. The contrast enhancement in LYH is generally more uniform.

Another distinctive feature reported in LYH is the presence of a low signal around the pituitary gland on MRI scans, similar in intensity to that of the bony cortex. This is referred to as a "dark signal" and is believed to reflect the fibrosis resulting from chronic pituitary inflammation.