Head injury (major cause)Read More

• Brain surgery
• Radiation treatment to the head or neck
• Lack of blood flow to the brain or pituitary gland (stroke) or bleeding (hemorrhage) into the brain or pituitary gland
• Certain medications, such as narcotics, high-dose corticosteroids such as prednisone, or certain cancer drugs called checkpoint inhibitors
• Inflammation of the pituitary gland caused by an abnormal immune system response (hypophysitis)
• Pituitary tumours, or tumours/diseases of the hypothalamus, a part of the brain above the pituitary. The hypothalamus produces hormones that directly affect the activity of the pituitary gland.
• Infections of the brain, such as meningitis, or infections that can spread to the brain, such as tuberculosis or syphilis
• Infiltrative diseases, which affect multiple parts of the body, including sarcoidosis, an inflammatory disease occurring in various organs; Langerhans cell histiocytosis, in which abnormal cells cause scarring in numerous parts of the body; and hemochromatosis, which causes excess iron deposits in the liver and other tissues
• Severe loss of blood during childbirth, which may cause damage to the front part of the pituitary gland (Sheehan’s syndrome or postpartum pituitary necrosis.
• An inherited genetic mutation, which affects the pituitary gland’s ability to produce one or more of its hormones. This can start at birth or in early childhood.
• Hematopoietic stem cell transplants

In some cases, the cause of hypopituitarism is unknown.

Source: Hypopituitarism – Symptoms and causes – Mayo Clinic