We present the case of a 40 year old man presenting at first consultation an idiopathic fast-onset and severe polyuro-polydipsic syndrome (diuresis of 10 l/24 hours, with urine osmolality of less than 50 mOsm/kg and urine gravity lower than 1001). Clinical examination showed pallor and decreased pilosity at an asthenic patient with limited lesions of vitiligo and loss of libido. Water deprivation test showed the persistence of excretion of highly diluted amounts of urine, confirming the diagnosis of diabetes insipidus. The patient responded spectacularly to therapy with sublingual desmopressin, with a decrease of diuresis to under 2500 ml/24 hours and an increase of urine gravity to 1010 under a dose of 60 μg×3/day, supporting the diagnosis of central diabetes insipidus. Serum testosterone was of 1.01 ng/ml (normal range between 2.6 and 10 ng/ml) and low-normal LH and FSH (LH=1.5 mU/l and FSH=2 mU/l) suggesting the presence of central hypogonadism. Serum fT4 was of 0.545 ng/ml (normal range between 0.9 and 1.9 ng/ml) with normal TSH (1.6 mIU/l) suggestive for central hypothyroidism. Corticotroph axis was undamaged (morning plasma cortisol of 15.5 μg/dl and ACTH of 38.9 pg/ml). Osteodensitometry revealed osteopenia. MRI investigation of the hypothalamo-pituitary region showed a small pituitary gland (7/3/6 mm) accompanied by partial empty sella without images of pituitary adenomas and absence of the native hypersignal of the neurohypophysis. The pituitary stalk was deformed, taking a nodular shape with dimensions of 4/5/6 mm. This image was highly suggestive for neuroinfundibular hypophysitis, most probably of autoimmune origin. Injections with testosterone undecanoate every three months and daily oral supplementation of thyroid hormones added to desmopressin therapy significantly improved patients quality of life. Autoimmune associations of the anterior and posterior pituitary are very rare and may raise difficulties of diagnosis and therapeutic decisions.
20 - 23 May 2017
European Society of Endocrinology