Endocrine Abstracts

An 80-year-old woman was diagnosed with malignant epithelioid mesothelioma on 26/02/2025 following presentation with a left pleural effusion. Thoracoscopy with biopsy confirmed the diagnosis, and an indwelling pleural catheter (IPC) was inserted on 26/03/2025 for recurrent effusions. She was started on combination immunotherapy with ipilimumab and nivolumab, receiving her first cycle on 15/05/2025. Following her second cycle, thyroid function tests showed initial thyrotoxicosis that later evolved into hypothyroidism with a free T4 of 6 pmol/l. She was diagnosed with immune checkpoint inhibitor (ICI)-induced thyroiditis and commenced on thyroxine replacement. After her fourth cycle on 17/07/2025, she was admitted with dizziness, confusion, and palpitations. Investigations revealed hyponatremia (Na 113 mmol/l), low cortisol (31 nmol/l), and evidence of secondary adrenal insufficiency consistent with ICI-induced hypophysitis. Pituitary profile results (FSH 3.2 IU/l, LH <0.3 IU/l, IGF-1 6 µg/l, prolactin <50 mIU/l) supported the diagnosis. She was started on hydrocortisone, resulting in clinical and biochemical improvement. A month later, she re-presented with fatigue and lethargy. She was alert and hemodynamically stable. Biochemical investigations showed blood glucose 27 mmol/l, pH 7.22, bicarbonate 17.3 mmol/l, and ketones 6 mmol/l, consistent with diabetic ketoacidosis (DKA). She was admitted to the high-dependency unit and managed according to DKA protocols, alongside intravenous hydrocortisone for adrenal insufficiency. Her C-peptide was low (7 pmol/l), confirming absolute insulin deficiency. A diagnosis of ICI-induced diabetes presenting with DKA was made. Immune checkpoint inhibitors can cause diverse endocrine immune-related adverse events, most often involving the thyroid, pituitary, adrenal, and pancreatic glands. While single gland involvement is relatively common, multiple endocrine dysfunctions are rare, affecting approximately 1–2% of patients, particularly with combination therapy. Triple endocrinopathies such as thyroiditis, hypophysitis, and diabetes mellitus are extremely uncommon, with an estimated incidence of around 0.02%.