Endocrine Abstracts

Adipsic hypernatremia, a rare hypothalamic disorder characterized by a loss of thirst in response to hypernatremia is more often reported in children. An autoimmune mechanism has been recently demonstrated. We report two cases.

Case1: A lean 67-year-old female, with a history of multilocular sclerosis, was admitted, for severe hypernatremia (162 mmol/l) with low ADH level (0.5 pmol/l; N: 0.5-2). She did not complain of thirst, despite ideomotor slowing and a skinfold. Diuresis was 1.40 l/24 h. Pituitary assessment showed mild hyperprolactinemia, a Nugent test at 11.5 mg/dl (n <1.8 mg/dl) with low TSH level (0.08 uU/ml (n 0.4-3.6)). MRI showed pituitary stalk nodular thickening. Etiological research only showed SFOAb. Treatment with desmopressin allowed improvement of ideo-motor slowing and natremia (145 mmol/l). The pituitary stalk thickening had partially regressed one year later.

Case2: An overweighed 38-year-old lady, was referred for a first hypernatremia episode (160 mmol/l) in 2013 after an acute pancreatitis complicated with cardiovascular collapse. She had no polyuria-polydipsia, did not feel thirst, and was irregularly menstruated. Initial pituitary assessment showed gonado-somatotropic insufficiency, mild hyperprolactinemia, normal thyroid and adrenal function. Keeping diagnosis was possible pituitary ischemia. The patient was advised to drink at least 2 liters/day and remained asymptomatic except for infertility. Three other episodes of pancreatitis occurred, the only identified cause being heterozygosity for a CFTR variant. In 2021, a new work-up showed similar pituitary profile as in 2013, hypernatremia (150 mEq/l), negative autoimmune panel, and normal CRP, IgG4 and pituitary MRI. A month later, a 5^th pancreatitis with severe bradycardia (30-35/bpm), hypothermia, low blood pressure and severe hypernatremia 170 mmol/l (ADH: 0.8 pmol/l) required ICU admission. Cortisol and thyreotrope deficit were present, with persistent hyperprolactinemia and somato-gonadotropic insufficiency. She initially improved with rehydration, hydrocortisone 200 mg/day and levothyroxine. Polyuria or thirst were absent. Hypernatremia worsened as soon as rehydration/hydrocortisone were tapered. Desmopressin allowed clinical improvement with a 10 mmol/day natremia decrease. On day 3, a seizure revealed brain hematoma and CT signs of vasculitis. Vasogenic edema finally leds to death.

Conclusion: These two cases of adipsic hypernatremia in adult female patients are possibly related to an autoimmune neurohypophysitis in the context of MS in case1 and systemic inflammatory/autoimmune disease explaining both the hypothalamic and pancreatic involvement in case2 Despite the lack of polyuria-polydipsia syndrome, desmopressin treatment improved clinical status and natremia, but should perhaps be used more cautiously than usually recommended. Autoimmune causes can today be proven and may help to adjust the treatment.