Diabetes insipidus and secondary hypogonadism due to vasculitis of the pituitary gland

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.