Endocrine Abstracts

An 82 year old lady was admitted under the general medical take with a fall and reduced consciousness. She had a history of two previous trans-sphenoidal surgeries for Cushing’s disease 30 years prior, with subsequent cranial diabetes insipidus and panhypopituitarism. Trans-sphenoidal surgery failed to control her cortisol excess, and resulted in a bilateral adrenalectomy. Medication history included full hormone replacement therapy including oral desmopressin 100 mg three times daily. Initial biochemistry revealed significant hyponatraemia with a sodium of 110 mmol/l (reference range 133-146 mmol/l). Plasma osmolality 232 mOsm/kg (275-295 mOsm/kg), with paired urine osmolality of 263 mmol/kg (50-1200 mmol/kg) and urinary sodium 97 mmol/l. Cortisol was low in keeping with known adrenalectomy, and thyroid function tests demonstrated secondary hypothyroidism with a suppressed TSH and normal T4. Clinically, the patient was hypovolaemic, and fluid replacement was initiated with slow IV 0.9% saline, and desmopressin was withheld. Due to low conscious level, a CT head was performed which revealed no acute change. A capillary blood sugar was checked and was found to be low at 2.2 mmol. Prompt treatment to reverse hypoglycaemia was given, as well as IV hydrocortisone given the history of adrenalectomy. Sodium gradually responded to fluid resuscitation and a lower dose of desmopressin was re-introduced due to polyuria, to avoid over-correction of sodium. She was admitted to the medical high dependency unit to monitor her conscious level and facilitate frequent blood sampling. A collateral history was obtained from the patient’s next of kin who explained that the patient had been suffering from polyuria, likely secondary to a urinary tract infection given raised inflammatory markers. However, she believed the polyuria to be secondary to her diabetes insipidus, treating with extra doses of desmopressin at home. The profound hyponatraemia was acute, as her biochemistry was within normal range a few months prior to admission. It was felt likely that this was a case of hypovolaemic hyponatraemia secondary to excess desmopressin. This case highlights the importance of patient education when prescribing hormone replacement, ensuring that sick day rules are followed.