Endocrine Abstracts

Introduction: Hyponatriemia is one of severe postoperative water-electrolyte disturbances. This condition is usually caused by syndrome of inappropriate secretion of antidiuretic hormone or cerebral salt-wasting syndrome which require different treatment approaches.

Case presentation: A 61-year-old woman was referred to tertiary care center with non-functioning pituitary macroadenoma. The patient had been suffering from headaches for 4 later years and had been treated with antihypertensive therapy that included ACE inhibitors and 12.5 mg of hydrochlorothiazide for several years. Macroadenoma was detected 2 years ago and in 2012 the MRI showed rapid suprasellar tumor growth.

At presentation: TSH 0.43 mIU/ml (0.25–3.5), fT₄ 15.31 pmol/l (9–20), ACTH 22.21 mg/ml (7–66), cortisol 436.6 nmol/l (123–626), FSH 19.6 U/l, LH 24.3 U/l, prolactin 214.1 mU/l (90–540), IGF1 76.67 (54–210). MRI revealed pituitary adenoma 16×20×13 mm with supra- and parasellar extensions. Intraoperatively the tumor occupied all of the sella space, infiltrated the pituitary and was closely attached to the back wall of the sella turcica.

The postsurgical period starting from 2d p.o. day was complicated by antidiuresis (fluid intake 2000–2700 ml, diuresis 1000–1200 ml), neurological disturbances (fatigue, vertigo, shaky walk). Postoperative hypothyroidism and hypocortisolism were excluded. The lab tests were only notable for hyponatriemia – 126 mmol/l (135–146). The i.v. therapy with normal saline (3% was not available), oral fluid intake restriction, increased oral salt intake, fludrocortisone 0.1 mg a day didn’t correct the clinical situation with variable electrolyte values in subsequent 4 days (Na 127–117 mmol/l, K 4.0–3.6 mmol/l, Cl 93–80 mmol/l, plasma osmolality 0.274–0.243 Osm/kg with inappropriately high urine osmolality 0.541–0.470 Osm/kg). The patient’s condition improved and Na normalization (139 mmol/l) occurred only after discontinuation of hydrochlorothiazide. After that fludrocortisone was withheld and no water-electrolyte disturbances were detected at follow-up control. Thereby, this clinical situation was considerate as thiazide-induced antidiuresis.

Conclusions: The case of our patient raises the problem of hard differential diagnosis and treatment of hyponatriemia in patients undergoing transsphenoidal surgery.