A 36-year-old man was admitted to the hospital with polyuria, nycturia, polydipsia
            (he drank 8 – 10 liters a day yet he still felt thirsty) as well as headache, dizziness,
            fatigue and loss of efficiency since 4 weeks. His medical history was otherwise normal.
            Clinical examination revealed no abnormalities. The polydipsia in combination with
            low urine osmolality (102 mosm/kg) were highly suggestive of diabetes insipidus. Therefore
            we performed a water restriction test. With water deprivation, diuresis and low urine
            osmolality persisted and serum sodium levels rose from 145 mmol/l to 154 mmol/l. Oral
            desmopressin resulted in normalisation of serum sodium as well as urine osmolality,
            confirming the diagnosis of central diabetes insipidus. Further endocrine examinations
            were consistent with a secondary hypogonadism (Testosteron 6,98 nmol/l, LH 3,4 mIU/ml,
            FSH 1,9 mIU/l). The other hypothalamic-pituitary axes were not affected. Pituitary
            MRI revealed a contrast-pooling pituitary lesion (8 × 7 x 6 mm), suitable for either
            a pituitary adenoma, a craniopharyngeoma or a lymphocytic hypophysitis. A diagnostic
            biopsy was performed. The histology demonstrated an active vasculitis of the small
            vessels without depositions of complement or IgG or granulomas. All immunological
            tests (e.g. ANCA, IL-2, ACE, neopterin, immunglobulins) were normal. We found no other
            manifestations of systemic vasculitis. In the CT scan of the thorax we found no indication
            for sarcoidosis. The patient started treatment of high-dose steroids and azathioprine.
            He also requires testosterone and desmopressin substitution. In summary, we report
            the rare case of a patient presenting with diabetes insipidus and secondary hypogonadism
            due to restricted vasculitis of the pituitary gland without signs of systemic vasculitis.