Endocrine Abstracts

Background: Arginine Vasopressin (AVP), also known as antidiuretic hormone (ADH), is secreted from posterior pituitary and plays a vital role in regulating water balance and serum sodium levels. Arginine Vasopressin Deficiency (AVP-D) previously known as central diabetes insipidus is well recognized complication following pituitary surgery. Perioperative monitoring of urine out and sodium levels is essential. When patient produces excessive urine for more (>50 ml/kg/hour for more that 2 hours, AVP-D is suspected. Patient needs urgent endocrine review and treatment with desmopressin. This case illustrates a patient developed AVP Deficiency on the third postoperative days following pituitary surgery for pituitary apoplexy.

Case: A 68-year-old male was admitted under the neurosurgical team for semi urgent Trans sphenoidal surgery. He presented with sudden onset headache and bitemporal visual loss in a regional hospital ad he was diagnosed with pituitary apoplexy leading to partial hypopituitarism and development of severe hyponatremia. He was managed with levothyroxine, and his sodium was normalized at the time of review by neurosurgical team. He did not require hydrocortisone given normal morning cortisol. He had MRI guided Endoscopic trans sphenoidal hypophysectomy (ETSH) on 26/06/2025. He received glucocorticoid cover perioperatively. Surgery was uneventful. He was monitored post operatively by daily endocrine review. On post operative day three, he developed significant polyuria, producing 400-500 ml/ hours for several hours equating to >50 ml/kg/hour for three consecutive hours. The patient reported increased thirst and was allowed to self-regulate fluid intake.

Laboratory tests showed:

• Serum sodium:145 mmol/l

• Serum Osmolality: 296 mOsm/kg

• Urine osmolarity: 83 mOsm/kg and

• Urine specific gravity was <1.005

These findings were diagnostic of AVP deficiency was given a single dose of intravenous desmopressin 1.0 ug IV which resulted in rapid symptomatic and biochemical improvement. He could not wait for further monitoring and was discharged on hydrocortisone, levothyroxine and desmopressin 100 microgram with clear instructions to use only if urine output exceeds 50 ml/kg/hr for > 2 hours. with advice to monitor input and output and repeat sodium in 2-3 days. His followed up back in regional hospital demonstrated stable electrolytes, normal urine output and good recovery.

Discussion Points: AVP deficiency often rises after surgery, but it can be delayed –how long monitoring must be continued? Pituitary apoplexy cases may have variable recovery of pituitary function, including transient or permanent AVP deficiency. Should we measure co peptin post pituitary surgery as it has good but no excellent accuracy.