Pituitary Stalk Lesions: Causes and Diagnostic Challenges.

The pituitary stalk (PS) is a funnel-shaped structure that connects the hypothalamus to the pituitary gland. It contains some anterior pituitary cells, the hypophyseal vessels, and the axons of neurons whose bodies are located in the hypothalamus and terminate in the posterior pituitary gland, where they store and release arginine vasopressin and oxytocin. The PS is best visualized by magnetic resonance imaging. PS thickening (PST) is often associated with arginine vasopressin deficiency, but it can also present with anterior pituitary hormones deficits or normal pituitary function. PST can be an isolated finding, or be expression of a multisystem infectious, inflammatory, or neoplastic process. Accordingly, these cases are best managed with the input of pituitary specialists from different disciplines. Although PS biopsy can provide a pathologic diagnosis, this is an invasive procedure that requires an experienced neurosurgeon and carries significant risks. This review discusses the causes and symptoms of PST, and addresses the demographic, history, physical examination, biochemical and radiological features that can help the endocrinologist in identifying the most likely cause of PST in any given patient, and to decide when biopsy is needed.