Endocrine Abstracts

Introduction: The overall incidence of pituitary involvement in leukaemia is reported to be 0.6%, and it is considered extremely rare in Acute Myeloid Leukaemia (AML) with unknown frequency. Literature search identified few published cases of pituitary AML involvement causing hypopituitarism and Arginine Vasopressin deficiency (AVP-D), but there are no case reports of SIADH.

Case Presentation: 29 years male presented with tonic-clonic seizures and euvolemic hyponatremia with sodium of 122mmol/l, and biochemistry supporting SIADH (plasma osmolality 258 mmol/kg, urine osmolality 318 mmol/kg, urine sodium 28 mmol/l). He has underlying complicated AML diagnosed 2 years earlier and he underwent allogenic stem cell transplantation 3 months prior to presentation. His pituitary MRI showed enhancing lesion infiltrating sella and suprasellar cistern, with nodular enhancement within infundibulum and right side of hypothalamus. His posterior pituitary bright spot was absent, but he had no symptoms of AVP-D. His lumbar puncture showed blast cells, confirming CNS infiltration. His pituitary profile showed raised prolactin 2867mu/l (56-278), testosterone 5.3nmol/l (10-27.6), LH 2.6iu/l (1.2-8.6), and FSH1.1iu/l (1.3-19.3), normal IGF-1and thyroid function. His cortisol was considered reasonable at 363nmol/l and he did not require hydrocortisone cover. His imaging was in keeping with leukemic pituitary infiltration. He was treated with cytarabine-venetoclax chemotherapy and intrathecal cytarabine, followed by cranio-spinal and pituitary radiotherapy. He showed immediate clinical, radiological and biochemical response to treatment within two weeks including rapid reduction in pituitary mass, normalization of sodium and prolactin and recovery of hypothalamic-pituitary-gonadal (HPG) axis in 4 months.

Discussion: Mechanism of SIADH and hyperprolactinemia in our case is likely due to infiltration of pituitary stalk, with hyperprolactinemia causing HPG axis suppression. This is the first case report of co-existing AML, SIADH, and partial hypopituitarism reflecting the importance of coordination between Endocrinology, Haematology and Pituitary MDT to promptly diagnose and treat such cases.