Endocrine Abstracts

A 64-year-old lady presented feeling unwell with nausea, vomiting, headaches and dizziness. She was taking sulpiride for schizophrenia and had an 8-year history of hyponatraemia. The hyponatraemia, was associated with mild hyperprolactinaemia, prompting investigation for hypopituitarism twice previously by endocrinologists in a different hospital. Secondary adrenal insufficiency had been excluded on the basis of: cortisol 576 nmol/l at 30 min after 250 mcg synacthen and cortisol 538 nmol/l at 30 mins after 1 mcg synacthen. Pituitary MRI was reported as showing no tumour. The biochemical findings were attributed to Sulpiride.

On this admission, sodium was 116 mmol/l, TSH 1.93 mlU/l, serum osmolality 252 mOsm/l, urine osmolality 566 mOsm/l, Examination, chest X-ray and admission bloods were normal. Of 09.00 a.m. cortisol was 114 nmol/l. Of 250 mcg synacthen test: cortisol 328 nmol/l at 0 min and 627 nmol/l at 30 min. Sulpiride was stopped, but she remained hyponatraemic.

On endocrine review she appeared clinically hypopituitary. Baseline pituitary function showed low fT4 (6.5 pmol/l; NR 11–26) with inappropriately normal TSH (1.93 mlU/l), low post menopausal gonadotrophins (LH 5.5 U/l, FSH 15.0 U/l), and high prolactin (1433 mU/l). Repeat 250 mcg synacthen test: cortisol 134 nmol/l at 0 min, 422 nmol/l at 30 min, and 500 nmol/l at 60 min.

A Glucagon test was stopped at 120 min due to possible adrenal crisis requiring fluids and parenteral hydrocortisone. Peak cortisol was 204 nmol/l (basal cortisol 120 nmol/l), peak GH 4.0. IGF-1 was 4.7 nmol/l (NR 6.0–36.0). Pituitary MRI revealed an empty sella.

A diagnosis of hypopituitarism of uncertain aetiology was made and treatment commenced with replacement steroids and thyroxine. Clinically she improved within weeks associated with normalisation of sodium.

A high index of clinical suspicion is often required to make a diagnosis of hypopituitarism in the elderly, presenting with euvolaemic hyponatraemia. A ‘normal looking’ 30 min cortisol during synacthen testing does not completely eliminate the diagnosis of secondary adrenal insufficiency if the clinical probability is high.