Neurology of the pituitary

The anterior pituitary hormones are essential for reproduction, growth, metabolic homeostasis, stress response, and adaptation to changes in the external environment. Each pituitary hormone is secreted in a distinctive pulsatile manner reflecting its regulation by the central nervous system through a complex interaction between hypothalamic neuroendocrine pathways, feedback effects from peripheral target gland hormones, and intrapituitary mechanisms. While the most common cause of a pituitary mass is an adenoma, the differential diagnosis is broad and includes pituitary hyperplasia, lymphocytic hypophysitis, craniopharyngioma among others. Patients with pituitary adenomas can be asymptomatic or present with symptoms due to mass effect, pituitary hormone dysfunction, or both. Prolactinomas represent 40% of pituitary adenomas, the majority of which are microadenomas. Hyperfunction of growth hormone and ACTH are far less common, while TSH-producing tumors are exceedingly rare. Hypopituitarism in patients with pituitary adenomas can be partial or complete. The clinical picture will depend on the type, degree, and rapidity of onset of pituitary hormone deficiency. An MRI specifically focused on the sellar region is the imaging modality of choice to detect pituitary pathology. Management of pituitary tumors ranges from observation of nonfunctioning microadenomas through medical, surgical, and radiotherapeutic approaches dependent on tumor type, function, size, and invasiveness.