Primary hypophysitis — also called idopathic hypophysitis — is a rare inflammatory condition of the pituitary gland and is believed to be an autoimmune disorder. Immune cells (primarily leukocytes) infiltrate the pituitary gland and gather into a mass that can mimic a pituitary tumor. Like a pituitary tumor, the mass can press on the pituitary gland, causing hormonal dysfunction. It can also compress the optic chiasm, located just above the pituitary gland, and affect vision. Sometimes hypophysitis can be distinguished from a pituitary tumor on an MRI if there is no clear gland-tumor interface or if there is clinical suspicion, and these can be presumptively treated with medications. However, often the only way to obtain a definitive diagnosis is through biopsy of the mass. Inflammation can also cause destruction of pituitary gland tissue and transient or permanent endocrine dysfunction.
There are two main types of primary hypophysitis: lymphocytic hypophysitis and giant cell granulomatous inflammation. Lymphocytic hypophysitis is the more common of these two conditions and is more common in women than men. It often occurs during or just after pregnancy, and can be associated with the inability to lactate but it does not affect the fetus or pregnancy. Lymphocytic hypophysitis also frequently occurs together with other autoimmune disorders. There is no typical pattern of symptoms seen with hypophysitis, but below are some of the more common symptoms experienced by patients treated at the CCPD.
The most common symptoms of lymphocytic hypophysitis result from compression of the gland or optic structures:
- Vision problems (such as loss of vision, blurred vision or double vision)
A direct result of the autoimmune attack on the pituitary gland is a reduction several pituitary hormones, which can lead to several other conditions, such as adrenal insufficiency, hypothyroidism, hypogonadism, and diabetes insipidus. Symptoms of these conditions can include:
- Polyuria (excessive urination)
- Polydipsia (excessive thirst)
- Decreased libido
- Erectile dysfunction
- Weight loss
- Visual disturbance (such as loss of vision or double vision)
- Diabetes insipidus
Symptoms of primary hypophysitis can be relieved with medication and sometimes with surgery to reduce the size of the mass that may be causing headaches or visual disturbances. In addition to reducing the size of the mass, surgery can provide tissue for a definitive diagnosis. Radiosurgery or lympholytic drugs can also be used to reduce the size of the mass for patients who are not surgical candidates or who do not wish to undergo surgery. With primary hypophysitis, leukocytes and plasma cells often infiltrate throughout the entire pituitary gland, so the goal of surgery is not to remove the entire mass as it is with surgery for pituitary tumors. Surgery rarely improves pre-existing endocrine dysfunction and is not curative. This is especially true for patients with hyperprolactinemia, diabetes insipidus or hypopituitarism. Medical therapy is aimed at treating endocrinopathies and replacing deficient hormones.