RT Journal Article SR Electronic T1 Hyponatraemia and hyperpigmentation in primary adrenal insufficiency JF BMJ Case Reports JO BMJ Case Reports FD BMJ Publishing Group Ltd SP e227200 DO 10.1136/bcr-2018-227200 VO 12 IS 3 A1 Bernadette Johanna Maria Benner A1 Jelmer Alsma A1 Richard A Feelders YR 2019 UL http://casereports.bmj.com/content/12/3/e227200.abstract AB Hyponatraemia is a common electrolyte disturbance with multiple causes. We present a case of a 49-year-old Caucasian female with cholangiocarcinoma, who had a hyponatraemia which was initially assumed to be based on a syndrome of inappropriate antidiuretic hormone secretion as paraneoplastic phenomenon. At physical examination, hyperpigmentation was seen and multiple episodes with syncope were reported. Subsequent endocrine assessment with a synthetic adrenocorticotropin hormone (ACTH) stimulation test and measurement of ACTH levels revealed primary adrenal insufficiency also known as Morbus Addison. We started hydrocortisone and fludrocortisone replacement therapy, resulting in resolving of symptoms, hyponatraemia and hyperpigmentation.