An unconventional case of hypokalemia

: Hypokalaemia is a common clinical problem. The underlying pathophysiology maybe one of them: insufficient potassium intake, excessive urinary or GI losses, and transcellular shifts. CLINICAL CASE: 36/F presented with c/o B/L lower limb weakness for 3 days. She had no respiratory or swallowing difficulty and was able to move her neck muscles. No bowel or bladder incontinence. The patient was not on diuretics. A significant past history of similar complains 4 years & 2years back. Both times, she was evaluated to have hypokalemia and was treated with oral and IV K supplements. But, cause was not determined. She was diagnosed with T2DM 4 years back when she presented with irregular menses. Her other medical problems included PCOS (on OCPS), hypertension and dyslipidemia. There is a strong family h/o diabetes, & a family h/o breast CA. There were no symptoms of recent or chronic vomiting or diarrhea. She did not have any symptoms of thyrotoxicosis and was not taking beta-adrenergic agonists. She also denied treatment with corticosteroids. O/E, the patient was obese. BMI-29.0kg/m2, HR, 90bpm, BP 150/100mmHg. Acanthosis nigricans was + around the neck. The rest of the examination was normal. Initial lab results - K level 2.0mmol/L. 24hr urinary K-21mEq/day. ABG-Ph 7.49, bicarbonate 26.2mmol/L. S. Mg 1.5mg/dl. Plasma renin 5.09ng/dl, plasma aldosterone 0.63µiu/ml, A/R ratio of 8.08. The possibility of Cushing's syndrome was considered. Further evaluation, baseline 8am cortisol 19.6µg/dl. 1mg screening overnight dexamethasone suppression test (DST) - 17.56µg/dl (<1.8µg/dl). As it was positive, a confirmatory 0.5mg low dose DST was done. The 3rd day 8am S.Cortisol was 10.8 µg/dl (43.15% suppression). S.ACTH level-196pg/ml. A 24hr urinary cortisol-1284µg/dl. To differentiate between Pituitary and Ectopic Cushing's, overnight 8mg DST done. Baseline S.Cortisol repeated, 24µg/dl. After suppression, 15.9µg/dl (33.75%). MRI pituitary performed, a well-defined heterogeneously enhancing mass lesion (measuring 15×13 x11 mm) was noted in the sella with mild suprasellar extension. Cushing's disease - ACTH producing pituitary macroadenoma with mild suprasellar extension with no compressive features, presenting as hypokalemic paralysis Treatment: Transsphenoidal resection of the tumor S.cortisol repeated after 2 months-4.80µg/dl, after 3 months - 4.19µg/dl. T. Prednisolone 5mg was started, OD. S.cortisol repeated after 5 months - 10.65µg/dl. S. ACTH repeated after 1 month of surgery 101pg/ml. 4 months later, I/v/o persistent hyperpigmentation and poor glycemic control, MRI Pituitary repeated, some residual tissue noted. Patient was subjected to a session of radiotherapy and is currently doing well. CONCLUSION: An unusual case of hypokalemia with no obvious features of Cushing's Disease, presented as hypokalemic paralysis and metabolic syndrome, with features of ACTH excess. [Figure: see text]