Pituitary apoplexy is bleeding into or impaired blood supply of the pituitary gland. This usually occurs in the presence of a tumor of the pituitary, although in 80% of cases this has not been diagnosed previously. The most common initial symptom is a sudden headache, often associated with a rapidly worsening visual field defect or double vision caused by compression of nerves surrounding the gland. This is often followed by acute symptoms caused by lack of secretion of essential hormones, predominantly adrenal insufficiency.

The diagnosis is achieved with magnetic resonance imaging and blood tests. Treatment is by the timely correction of hormone deficiencies. In many cases, surgical decompression is required. Many people who have had a pituitary apoplexy develop pituitary hormone deficiencies and require long-term hormone supplementation. The first case of the disease was recorded in 1898.