Endocrine Abstracts

Cyclic Cushing’s syndrome (CCS) is a rare condition that involves recurring episodes of hypercortisolaemia, alternating with normocortisolemia at intervals ranging from a few days to several years. To diagnose CCS, it is necessary to demonstrate three cortisol peaks and two troughs. CCS is mostly seen in females and can be Adrenocorticotropic hormone (ACTH)-dependent or independent2. The common causes of CCS are Cushing’s Disease (55% ), ectopic ACTH syndrome (26%), and adrenal tumours (11% ). Around 18% of functioning adrenal incidentalomas exhibit cyclic autonomous cortisol production. We present a case of a 51-year-old marathon runner referred for evaluation of hypokalaemia (2.3 nmol/l) and bradycardia (38 beats/minute) associated with abdominal bloating, knee swelling, polyuria, lethargy, and weight loss of 2-3 kg in 1 week. The first episode was reported in July 2021, followed by further episodes in April 2022, and September 2022 each lasting for 1 week and he resumed marathon running after each episode. He was symptom-free on initial assessment without any clinical features to suggest Cushing syndrome. His potassium, and cortisol were normal with mildly elevated prolactin(420mU/l). Overnight Dexamethasone Suppression Test (ONDST), aldosterone renin ratio, and 24-hour urinary cortisol levels done while symptomatic, showed potassium 2.7 nmol/l, random cortisol level of 1728nmol/l, 24-hour urine cortisol (237 nmol/d), ACTH (453 ng/l) and post ONDST cortisol (361 nmol/l) suggesting ACTH-dependent Cushing’s Syndrome. MRI pituitary confirmed pituitary macroadenoma abutting the chiasm. He awaits transsphenoidal resection of pituitary macroadenoma with potassium supplements and thromboprophylaxis coverage for increased VTE risk associated with Cushing’s Syndrome. This case report highlights that though most patients present with typical clinical features, a minority of CCS patients present without clinical signs initially. Due to a lack of persistent high cortisol levels and variable clinical presentation, CCS is particularly challenging to diagnose.