Lymphocytic hypophysitis (LH) is a condition in which the pituitary gland becomes infiltrated by lymphocytes, resulting in pituitary enlargement and impaired function. It most often occurs in women in late pregnancy or the postpartum period, but can also occur in prepubertal or post-menopausal women, and in men. Symptoms of LH may include headache, visual field impairment and more rarely, double vision (diplopia). The exact cause is unknown but is thought to be autoimmune-related. Although some cases resolve on their own or after a short course of steroids, other cases cause persistent problems even with aggressive medical or surgical treatment.

Other features that occur more rarely and are related to alterations in pituitary secretions may include:

• hypoprolactinemia (deficiency of prolactin)
• subclinical hypopituitarism (decreased production of pituitary hormones with no symptoms)
• ACTH deficiency
• acute adrenal crisis
• hypogonadotropic hypogonadism (usually diagnosed only in males)
• isolated growth hormone (GH) deficiency

The exact cause of lymphocytic hypophysitis (LH) is still under debate and remains unclear. It has been suggested that LH has an autoimmune etiology. This has generally been supported by the frequent postpartum occurrence and the lymphocytic infiltration, as well as several histopathological, laboratory and clinical findings.

Many affected individuals only have headaches as a manifesting symptom, and there have been multiple reports of these individuals improving with glucocorticoids alone. Although the use of glucocorticoids or other anti-inflammatory and immunosuppressive drugs have been suggested as medical treatment, their long-term efficacy still needs to be confirmed. High-dose methylprednisolone pulse therapy (short, intensive administration given at set intervals) seems to be effective in about 30% of treated patients.

Transsphenoidal surgery (accessed "through the nose") to confirm diagnosis and save viable pituitary tissue may be required in individuals with symptoms or signs of severe compression. Visual improvement following decompression with this type of surgery has been reported. In some cases, pituitary biopsy is both diagnostic and therapeutic, because after this procedure a progressive recovery of pituitary function may occur.