lymphocytic hypophysitis ( hyp ) is a rare inflammatory condition classified in adenohypophysitis ( ahyp ) , infundibulo - neurohypophysitis ( nhyp ) and panhypophysitis . ahyp mainly occurs in women , often during pregnancy or postpartum period , causing hypopituitarism , while nhyp usually presents with diabetes insipidus ( di ) . diagnosis of hyp is based on endocrine dysregulation and abnormal findings on cranial magnetic resonance imaging ( mri ) . we present the case of a patient , who was admitted to our department with a suspected diagnosis of a pituitary adenoma , diagnosed as lymphocitic infundibulo - neurohypophysitis after more accurate neuroradiological and endocrinological investigations . her urinary osmolarity and plasma osmolarity were 70.5 mosm / kg and 317 mosm / kg respectively with oral free water intake . the peak plasma antidiuretic hormone ( adh ) level measured by radioimmunoassay was 1.3 pg / ml when plasma osmolarity was 317 mosm / kg . serum sodium and potassium concentration were 144 mmol / l and 4.1 mmol / l . urinary sodium and potassium levels were 108 mmol / l and 37 mmol / l respectively . cranial mri showed a left - sided adenohypophyseal mass featuring a pituitary adenoma ( figure 1a and b ) . the mass appeared to contact both internal carotid arteries without deviation of the stalk or connection to the optic chiasm . her past history included an intracerebral hemorrhage in 1996 treated by evacuation of the hematoma , decompressive craniectomy followed by reconstructive cranioplasty . basal anterior pituitary function tests were normal except for low increase of human growth hormone ( 18.10 ng / ml ) which was probably stress - related . the clinical signs , the results of the laboratory data and the evaluation of mri were not convincing upon the diagnosis of pituitary adenoma . mri showed a left - sided distended adenohypophysis with highly intense signal in the t2-weighting , without contrast enhancement in the t1-weighting . predominantly remarkable was the loss of signal intensity in the t1-weighted sequences of the neurohypophysis ( figure 1c ) . combining our test results we drew the diagnosis of nhyp as our conclusion and abstained from surgical procedure . the patient was discharged and was treated with 50 mg corticosteroid twice a day and desmopressin spray . six months later her condition was stable , but the symptoms were not declining . 
 figure 1(a ) t1 weighted magnetic resonance imaging : coronar section of the pituitary showing a thick pituitary stalk . ( b ) t2 weighted mri : in the transversal section section an adenoma of the left pituitary gland is suspected . ( c ) on the sagittal section of this t1 mri the neurohypophysis which is normally hyperintense is hypotintense . ( a ) t1 weighted magnetic resonance imaging : coronar section of the pituitary showing a thick pituitary stalk . ( b ) t2 weighted mri : in the transversal section section an adenoma of the left pituitary gland is suspected . ( c ) on the sagittal section of this t1 mri the neurohypophysis which is normally hyperintense is hypotintense . ahyp is considered to be an autoimmune reaction in the anterior pituitary gland frequently associated with female gender , pregnancy or presenting during the postpartum period . however , according to different autopsy series occurrence of ahyp could also been shown in males . ahyp most commonly presents with symptoms of sellar mass with or without varying degrees of hypopituitarism , whereas di is uncommon . nhyp is a distinct entity , first reported by imura , in which inflammation is confined to the hypothalamic - neurohypophysial system frequently presenting with di . di is a clinical syndrome , characterized by polyuria and polydipsia , which can be divided in central ( adh deficit ) and nephrogenic type ( adh - resistant ) . central di is usually caused by head trauma , infections , inflammations ( e.g. meningitis , hypophysitis ) or neoplasms ( e.g. adenoma ) . inflammatory processes of the hypophysis can be easily misdiagnosed because of their clinical and radiological features mimicking tumors in the sellar or parasellar region . hyp usually presents as symmetrical enlargement of the pituitary gland while it is asymmetrical in patients with adenoma . the stalk is thickened but non - deviated while deviation of the stalk is observed commonly in adenomas . patients with hyp show an intense and homogenous enhancement of the mass after gadolinium contrast and also a strip of enhanced tissue along the dura mater ( dural tail ) while patients with adenoma show a slightly delayed and inhomogenous enhancement . the neuroimaging findings that could lead in particular to the diagnosis of nhyp are the absence of abnormalities in anterior pituitary gland , the thickening of the pituitary stalk and the enlargement of the neurohypophysis . apart from these schematic differences it is important to note that some variants of nhyp may form a mass not localized in the neurohypophysial space but involving the adenohypophysis , thus resembling adenomas and other tumours . in these particular cases it is important to perform a high resolution mri focussed on the sellar region to notice the thickness of the stalk and the signal intensity of the neurohypophysis , that are the two cardinal signs that can lead to the correct diagnosis . in patients with the radiological findings mentioned above , presence of di and normal anterior pituitary gland function , if clinical and neuroimaging findings are typical of this disease , surgical intervention including biopsy should be avoided since it does not improve the diabetes insipidus and can also lead to further endocrine disturbance . spontaneous remission of this disease can occur but a treatment with immunosuppressive drugs like glucocorticoids is generally recommended , even if this therapy seems to be effective in only about 30% of all treated patients the patients should be examined in follow - up - examinations including mris closely to register the success of therapy and to avoid dysregulation of the endocrine system . hyp is a rare constellation with special clinical characteristics . despite defined radiological features to differentiate between hyp and adenoma the possibility of a misdiagnosis , and consequently unnecessary surgical procedures ,
a rare case of infundibulo - neurohypophysitis mimicking a pituitary adenoma is presented . a 69-years - old female patient developed polyuria and polydipsia . 
 laboratory analysis revealed central diabetes insipidus . no hormonal abnormalities . 
 cranial - magnetic resonance imaging ( mri ) showed a left sided mass in the adenohypophysis presuming a pituitary adenoma . 
 the mass had contact to both internal carotids . 
 admission to our department for neurosurgical treatment followed . 
 ophthalmologic examination and neurological examination yielded normal findings . 
 a second mri focussing on the sellar - region showed a left - sided ( t2-mri.hyperintense ) , distended adenohypophysis , without contrast enhancement in t1 . 
 the stalk appeared thickened . 
 t1-weighted sequences of the neurohypophysis showed loss of signal intensity . 
 we diagnosed an infundibulo - neurohypophysitis and abstained from surgical removal . 
 the patient was discharged under treatment with corticosteroids and desmopressin . 
 hypophysitis is rare and shows special clinical characteristics . despite defined radiological features to differentiate between hypophysitis and adenoma the possibility of misdiagnosis , and unnecessary surgical procedures , 
 should always kept in mind .