A 33-year-old Bruneian male presented with sudden onset polyuria and polydipsia. A water deprivation test confirmed central diabetes insipidus. Anterior pituitary function showed hypogonadotrophic hypogonadism. A magnetic resonance imaging (MRI) brain demonstrated enlargement of the pituitary stalk with a maximum diameter of 6.01mm. Investigation for secondary causes included a lumbar puncture which demonstrated mildly elevated cerebrospinal fluid hCG (11.4 IU/L), however other investigations including a testicular ultrasound and computed tomography of the chest, abdomen and pelvis, were unremarkable. Serial MRI brain showed reduction in size of the pituitary stalk, and he was diagnosed with likely lymphocytic hypophysitis.
The approach to a patient with pituitary stalk thickening consists assessment of anterior and posterior pituitary function and determining the cause, which could be neoplastic, inflammatory or congenital.
Lymphocytic hypophysitis is an autoimmune condition with infiltration of the pituitary with lymphocytes and eventual fibrosis. Definitive diagnosis can only be made via pituitary stalk biopsy, but there is no consensus on the indications for biopsy. In a study of 37 patients with pituitary stalk thickening no patients with lymphocytic hypophysitis had pituitary stalk thickening of >6.5mm initially or on serial imaging.1 In contrast, all cases of germinoma were either greater than 6.5mm initially or developed other abnormalities on serial imaging, and only one case of histiocytosis remained <6.5mm during follow-up. A suggested approach therefore is to perform pituitary stalk biopsy if the gland is >6.5mm in size, or enlarges to this value on serial imaging.
There is no evidence based guidelines on the management of lymphocytic hypophysitis. Options include monitoring alone as spontaneous resolution has been documented, or glucocorticoids. Surgery and radiation are reserved for mass effect. Overall, an individual approach is warranted, with regular monitoring of pituitary function and neuroimaging and consideration of biopsy if the lesion progresses.