Hypopituitarism is a rare condition characterized by deficient pituitary hormone resulting from damage to the pituitary gland (primary hypopituitarism) or from damage to the hypothalamus or pituitary stalk (secondary hypopituitarism). The most common cause in adults is pituitary tumors or adenomas. Other causes include sellar / parasellar tumors (usually craniopharyngiomas), inflammation, infection, surgery, radiation, traumatic brain injury, subarachnoid hemorrhage, and postpartum pituitary necrosis (also known as Sheehan syndrome). Causes of secondary hypopituitarism include inflammatory hypophysitis and germ cell tumors.

Patients usually have involvement of just one or some pituitary hormones, although they can also have deficiency of all pituitary hormones (panhypopituitarism). Onset is typically insidious and may go unrecognized by the patient. Rarely, onset may be acute and require immediate attention. Clinical signs and symptoms depend on specific pituitary hormones affected.