Endocrine Abstracts

Beta-adrenergic receptor blockers are widely used to manage conditions including cardiovascular disease, migraines, and hyperthyroidism. Drugs like bisoprolol have demonstrated prognostic benefits in heart failure. Given their broad use, awareness of both common and rare adverse effects is essential. We present a case of bisoprolol-induced hyperhidrosis with elevated 5-hydroxyindoleacetic acid (5-HIAA) levels. A 78-year-old man with a history of atrial fibrillation, overactive bladder and haemorrhoids presented to the outpatient clinic with excessive sweating that worsened over two years. His medications included bisoprolol, edoxaban, atorvastatin, and ramipril. Hyperhidrosis episodes lasted up to 30 minutes, occurring daily, sometimes worsened with spicy food. He reported flushing but denied palpitations, dyspnoea or weight loss, gastrointestinal or urinary symptoms. He reported weight gain of 8 kg over the past two years, had a 60-pack-year smoking history, but abstained from alcohol and caffeine. Physical examination showed no signs of parkinsonism or thyroid dysfunction. Initial investigations ruled out tuberculosis, aortic regurgitation, and endocarditis. Biochemical testing revealed an elevated 5-HIAA level of 507 μmol/24 h (reference range: 0.2–118 μmol/24 h), with normal chromogranin A, thyroid function tests, plasma metanephrines, renin-aldosterone levels, and gut peptides. Following an unremarkable CT thorax/abdomen/pelvis, an octreotide scan demonstrated focal uptake in the pancreatic head. MRI identified a possible small peripancreatic nodule but no definitive lesion explaining his symptoms was found. Surveillance was recommended after multidisciplinary review. Discontinuation of bisoprolol was subsequently followed by normalisation of 5-HIAA levels and marked symptom improvement. A follow-up MRI showed no evidence of the previously noted lesion. Lifestyle advice was provided with cardiology referral for alternative rate control therapy. Beta-blocker-induced hyperhidrosis is rare, with prior reports primarily linked to non-selective beta-blockers. This case highlights the unusual association of bisoprolol with hyperhidrosis. To our knowledge, there are no previous cases reported in the literature.