Endocrine Abstracts

A 54 year old male was referred for evaluation of Diabetes Insipidus in 2021 with a 12 month history of polyuria, polydipsia and nocturia 3-4 times per night. He always carried water with him and drank 750 ml overnight. He had a history of Ulcerative Colitis, enteropathic osteoarthritis and asthma. He was on Secukinumab monthly. Partial Central Arginine Vasopressin (AVP) deficiency was confirmed by a water deprivation test (serum osmolality >293 mOsm/kg, urine osmolality 300-750 mOsm/kg and <750 mOsm/kg post DDAVP). MRI Pituitary showed a thickened infundibulum with an absent posterior pituitary bright spot. He was trialled on 0.2 mg desmopressin nocte, titrated up to 0.1 mg BD and 0.2 mg nocte based on symptoms. The following tests were normal – sex steroid axis, morning cortisol, thyroid function, IGF-1, HbA1C, calcium, AFP, hCG and serum sodium. Autoantibody screen was negative. IgG4 was elevated at 5.998 g/l (normal range 0.039–0.864) and Serum ACE 67 U/l (normal 8–65). Following discussion with Rheumatology, a CT TAP in 2022 showed no retroperitoneal fibrosis, bilateral sacroiliitis or mediastinal lymph node enlargement. Bronchoscopy to evaluate for sarcoidosis and/or TB was negative. Repeat MRI pituitary in 2022 showed the pituitary infundibulum remained thickened although slightly improved. But in 2023 increased thickening of the infundibulum was reported consistent with progressive hypophysitis. Central AVP deficiency arises from inadequate production or secretion of arginine vasopressin, usually due to neurohypophyseal damage. The causes include trauma, neoplasm, vascular accident, granulomatous disease including sarcoidosis, infection including TB, inflammatory and autoimmune hypophysitis, drug-induced or idiopathic. The water deprivation test is the gold standard for diagnosis, and partial central AVP deficiency is confirmed if urinary concentration rises to 300-800 mOsm/kg with a greater than 9% rise after administration of DDAVP. Treatment with desmopressin aims for symptom control (Refardt J et al. Diabetes Insipidus: An Update. Endocrinol Metab Clin North Am. 2020). Hypophysitis is a rare inflammatory disorder involving the pituitary gland and infundibulum. At least 5 clinicopathologic types have been described: IgG4-related, lymphocytic infundibuloneurohypophysitis, granulomatous, xanthomatous, necrotizing disease or, more common recently, immune checkpoint inhibitor use. Pituitary biopsy is required for definitive diagnosis (Melmed S et al. Williams Textbook of Endocrinology 14th Edition). Our patient is currently clinically well and symptom-controlled on desmopressin. The risk of a pituitary biopsy is thought to outweigh the benefits of a clinical diagnosis at present. We are considering treatment with high- dose glucocorticosteroids in light of the recent progressive hypophysitis noted on MRI.