Lymphocytic Hypophysitis

Etiology

Hypophysitis can be categorized based on etiology as primary or secondary.[5] Primary hypophysitis can be further categorized based on histology as lymphocytic, granulomatous, xanthomatous, IgG4 related, or mixed and based on anatomy as lymphocytic adenohypophysitis, lymphocytic infundibuluneurohypophysitis or lymphocytic panhypophysitis.[4][6] Lymphocytic adenohypophysitis affects the anterior pituitary gland, lymphocytic infundibuloneurohypophysitis affects the posterior pituitary gland, and lymphocytic panhypophysitis affects both the anterior and posterior pituitary glands.[2] 

While primary hypophysitis describes pituitary gland inflammation itself, secondary hypophysitis describes pituitary gland inflammation due to diseases such as sarcoidosis, hemochromatosis, amyloidosis, granulomatosis with polyangiitis, tuberculosis, syphilis, and pituitary gland inflammation due to medications such as immunomodulatory drugs including immune checkpoint inhibitors such as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed death 1 (PD-1) medications.[5] 

Lymphocytic hypophysitis itself was first described in 1962 by Goudie and Pinkerton when they noted it to be the most common form of primary hypophysitis and associated it with autoimmune pathogenesis.[2] It is also referred to as autoimmune hypophysitis at times.[3]

Epidemiology

The prevalence of all the types of hypophysitis is low, with an incidence of approximately 1 in 9 million.[2] However, it is thought that this may be an underestimate, especially due to the recognition of IgG4 related disease and the recent use of immune checkpoint inhibitors for cancer treatments, which have endocrine side effects affecting the pituitary gland.[4]

Lymphocytic hypophysitis itself was initially thought to be an autoimmune condition that affected women in the third trimester and the postpartum stage (first six months after delivery), however, it has now been known to occur in non-pregnant females and males as well. It is a rare condition that still affects women more frequently than men at a ratio of 8 to 1.[7]

Although cases have been reported in children and the elderly, the mean age of diagnosis for men is 44.7 years, and the mean age of diagnosis for women is 34 years. It has also been associated with other autoimmune conditions in 20 percent to 50 percent of cases.[5]

Histopathology

While histology provides a definitive diagnosis of lymphocytic hypophysitis, it requires biopsy or resection of the suprasellar or sellar tissue, which poses a high risk and therefore is not a very practical approach.[4] The histological evaluation shows the infiltration of the adenohypophysis with lymphocytes, plasma cells, and macrophages. The T and B lymphocytes that infiltrate the pituitary gland can also form lymphoid follicles with a germinal center.[2] Histological stains can also be used to identify inflammatory cells and can also be used to categorize the degree of lymphocytic infiltration.[4] 

The degree of lymphocytic infiltration corresponds to the degree of enlargement of the pituitary gland, which in turn places pressure on nearby structures, causing headaches, visual problems, and subclinical hypopituitarism. The subclinical hypopituitarism can resolve if the pituitary gland tissue is not completely destroyed. Fibrosis of the pituitary gland can also be seen as the disease progresses.[7] If the pituitary tissue is destroyed due to the extensive degree of lymphocytic infiltration, it is replaced by fibrous tissue, and symptoms of partial or complete hypopituitarism occur.

History and Physical

While lymphocytic hypophysitis was initially thought to only affect the anterior pituitary, it is now known to affect the posterior pituitary and pituitary stalk as well, causing inflammation and lymphocyte, macrophage and plasma cell infiltration of the pituitary gland.[7] Lymphocytic hypophysitis can lead to deficiencies in one or more pituitary hormones, causing central diabetes insipidus if the posterior pituitary gland is affected as well as central adrenal insufficiency and central hypothyroidism if the anterior pituitary gland is affected.[5][7] 

Other conditions that can occur due to pituitary inflammation include hypogonadotropic hypogonadism and growth hormone deficiency.[2] Enlargement of the pituitary gland can also compress the optic apparatus/chiasm and cause neuro-ophthalmic manifestations such as a decrease in vision and color perception.[8][4] 

Often times, headache is the first symptom and occurs at the onset of the disease and is usually followed by visual field defects/ophthalmoplegia and, at times, diplopia when the cavernous sinus, cranial nerves three, four and six are affected.[7] Eventually, pituitary destruction can occur due to infiltration and inflammation, and hypopituitarism can result in affecting almost all pituitary hormones.[7] Common symptoms include nausea, vomiting, fatigue, loss of libido, amenorrhea, and dizziness.[2]

Evaluation

Lymphocytic hypophysitis continues to be a diagnosis of exclusion, and histopathology with tissue biopsy is needed for a definitive diagnosis.[3] However, clinical, laboratory data, and imaging can all help with the diagnosis.[8] First and foremost, patients present with symptoms of hypopituitarism and must undergo pituitary hormone function evaluation.[7]

The hormones that need to be measured include prolactin, adrenocorticotropic hormone, cortisol, IGF-1, growth hormone, thyroid-stimulating hormone, free thyroxine, testosterone, luteinizing hormone, and follicle-stimulating hormone. Diabetes insipidus should also be evaluated by obtaining electrolyte levels, anti-diuretic hormone, serum, and urine osmolality, and water deprivation testing if needed.

About 20% to 50% of those with lymphocytic hypophysitis have been shown to have other autoimmune conditions.[5] At times, antipituitary antibodies and antihypothalamus antibodies have also been found. However, it is not always practical to obtain these antibodies.[2] However, assessment for other autoimmune and inflammatory diseases should be performed by obtaining complete blood count, complete metabolic panel, c-reactive protein, erythrocyte sedimentation rate, antinuclear antibody, and lupus antibodies at the very least.

Gadolinium-enhanced MRI of the pituitary is the imagining of choice, and it is important to distinguish lymphocytic hypophysitis from a pituitary adenoma. With a pituitary adenoma, MRI shows asymmetrical pituitary enlargement, with the pituitary stalk being deviated as well. However, in lymphocytic hypophysitis, the pituitary gland and the pituitary stalk is symmetrically enlarged, but there is no stalk deviation. MRI also shows a homogeneously intense pituitary with dura enhancement, also referred to as a dural tail along with arachnoid enhancement in lymphocytic hypophysitis.[4][7] 

In those with a pituitary adenoma, there is no enhancement of the dura or arachnoid. Despite these findings, radiological imaging cannot always distinguish between an adenoma and lymphocytic hypophysitis so easily, and in fact, at one point, 40% of patients with lymphocytic hypophysitis were misdiagnosed as having pituitary macroadenomas.[3] Often times, many of these patients are noted to have undergone surgery because a pituitary adenoma is suspected to be the cause of their symptoms.[7] However, this is not a surgical disease, and surgery should be avoided if a diagnosis can be made without histopathology. Surgery, however, is recommended if pituitary inflammation and infiltration are affecting a patient’s vision.[9]

In response to the high number of misdiagnosis, a scoring system, known as the Gutenberg scoring, was developed to correctly identify lymphocytic hypophysitis. This scoring system looks at various MRI features in an attempt to diagnose this disease prior to any surgical procedure.[3]

The scoring system and scoring are as follows:

• Age less than or equal to 30 receives a score of -1
• Current pregnancy or being less than or equal to 6 months postpartum receives a score of -4
• An increased stalk size receives a score of -5
• Increased gadolinium enhancement receives a score of -1
• Loss of pituitary bright spot receives a score of -2
• Pituitary volume greater than 6cmreceives a score of +2
• Sphenoid mucosal thickening receives a score of +2
• Heterogeneous gadolinium enhancement receives a score of +1
• Asymmetrical sellar enlargement receives a score of +3

A total score greater than 1 is suggestive of a pituitary adenoma, while a score of zero or less is suggestive of lymphocytic hypophysitis with a specificity of 99%, a sensitivity of 92%, and a positive and negative predictive value of 97%.[3]

Treatment / Management

The main goal of the treatment of lymphocytic hypophysitis is to manage any pituitary hormone deficiencies and to manage any mass-like effect that may occur due to pituitary gland enlargement. This treatment can consist of conservative management and the use of anti-inflammatory agents. Surgery or radiotherapy is rarely used. However, first and foremost, the pituitary function needs to be assessed and any pituitary hormone deficiencies need to be managed.[10] They should also be assessed for diabetes insipidus and treated accordingly if necessary. While there can be spontaneous resolution or regression of lymphocytic hypophysitis, if there is a high suspicion of lymphocytic hypophysitis steroid therapy is the mainline treatment of this condition.[4] 

However, if vision is affected, or if there is compressive mass like signs affecting nearby vital structures or if histology is needed to confirm the diagnosis, surgery becomes the main line of treatment. At times, patients require long term hormone replacement therapy, however, corticosteroid therapy, which has an anti-inflammatory response and can decrease the size of the mass lesion, can help patients regain pituitary function and decrease the need to be on lifelong replacement hormone therapy if recurrence after treatment does not occur. There is no consensus on the appropriate dosage and duration of glucocorticoid therapy and both these vary. One study in Germany had 32 patients treated with 20 to 500 mg daily of prednisolone equivalent glucocorticoids for a duration range of 4 days to a year.[11] 

Steroids should be tapered off accordingly based on the response as the number of adverse side effects has been increasingly reported. These adverse effects include weight gain, Cushing’s syndrome, edema, glaucoma, psychiatric symptoms, and diabetes mellitus. While there has been an initial good response to steroid therapy, there has also been a high rate of recurrence of approximately 38%. For those that show no improvement with corticosteroids or have relapsed after treatment with corticosteroids, immunosuppressive medications such as methotrexate, azathioprine, and cyclosporine can be used as well.[9] There have also been some cases where dopamine agonists such as cabergoline/bromocriptine have also been successfully used in those with hyperprolactinemia due to pituitary inflammation.[4]

Once again, it is important to note that surgery is only an option for those suffering from visual problems/ophthalmoplegia, have a mass like an effect from compression of nearby structures, or for those that have equivocal imagining findings and require histology for diagnosis. It does have the advantage of providing histological confirmation to correctly diagnose and manage lymphocytic hypophysitis and to exclude the diagnosis of a pituitary tumor. Surgery, which involves transsphenoidal or transcranial partial resection of the pituitary lesion or decompression of the mass, has a rate of recurrence of the lesion and associated symptoms of 11% to 25%. It was also noted that there is no relationship between the extent of the resection and the rate of recurrence. Surgical complications that have been noted include postoperative meningitis and rhinorrhea. There have also been cases where glucocorticoid therapy and surgery were both used.[11] However, if both these approaches and immunosuppressive therapy fail, fractionated radiotherapy can be used.

Differential Diagnosis

A detailed history and physical examination are helpful in diagnosing lymphocytic hypophysitis. However, without a tissue biopsy and with evidence of pituitary mass along with symptoms of hypopituitarism, the differential diagnosis continues to be large.[8] This differential diagnosis most commonly includes pituitary adenoma, however other differentials can be craniopharyngioma, Rathke cleft cyst, germinomas, pituitary apoplexy, and pituitary metastasis.[3][12][13] 

The differential diagnosis can also include infectious and inflammatory conditions as well. These include IgG4 hypophysitis, granulomatous hypophysitis which can be idiopathic or due to tuberculosis, syphilis, or sarcoidosis, Wegner’s granulomatosis and Langerhans cell histiocytosis.[4][5][6] Complete lab work and imaging need to be performed for further investigation.

Prognosis

Lymphocytic hypophysitis often has symptoms and features similar to that of a pituitary adenoma.[7] Previously, the diagnosis was made on autopsy, however, due to advancement in imaging, the number of cases that have been reported in the past three decades has increased. Because of lymphocytic infiltration of the pituitary gland and subsequent gland inflammation, hypopituitarism involving all pituitary hormones can occur. Treatment options vary based on symptoms and can include expectant observation to monitor for spontaneous remission, glucocorticoid therapy, immunosuppressive agents, partial resection of the pituitary lesion, and surgical decompression if nearby vital structures are at risk due to mass effect.[7] 

Diagnosis without definite histopathology can be difficult because some patients can present with no symptoms, however majority of them do present with headaches, visual problems, or other endocrine-related symptoms.[13] 

Diagnosis often lags behind the onset of symptoms.[14] Often, recurrence still occurs even after medical therapy and surgical therapy and this is why lifelong hormone replacement therapy is needed.[9] It is important to timely diagnose and appropriately treat hormone deficiency problems, especially adrenal insufficiency which has a high rate of morbidity and mortality associated with itself.[10] Despite the complications and difficulty diagnosing lymphocytic hypophysitis, once it has been diagnosed, it can be managed accordingly with steroids, surgery, immunosuppressive agents, continuous monitoring and the overall prognosis can remain good.[14]

Complications

It is essential to diagnose and appropriately manage lymphocytic hypophysitis as soon as possible due to the complications that follow.[14] Many patients have anterior pituitary hormone deficiencies and diabetes insipidus resulting in panhypopituitarism. Prolactin levels can also be decreased, normal or increased. It is very important to check cortisol and adrenocorticotropic hormone in order to diagnose and treat adrenal insufficiency as well which occurs as a result of lymphocytic hypophysitis.[10] 

Due to rapid development of secondary adrenal insufficiency, a cosyntropin stimulation test may be normal because there is not enough time for adrenal glands to atrophy. An insulin induced hypoglycemia test may be required to assess adrenal insufficiency early on. Other hormone deficiencies can occur and prolactin, IGF-1, growth hormone, thyroid stimulating hormone, free thyroxine, testosterone, luteinizing hormone, follicle stimulating hormone, electrolyte levels, anti-diuretic hormone and serum and urine osmolality should be measures as well.[4] 

Pituitary gland enlargement can also cause neurological symptoms such as visual field defects due to mass effect and can lead to compression of the optic nerve, optic chiasm and cavernous sinus cranial nerves III, IV and VI. Visual field defects can include poor color vision perception, ophthalmoplegia and diplopia.[4][7][8]