Endocrine Abstracts

Introduction: Hypophysitis is a rare pituitary inflammatory disorder that can mimic macroadenomas, often presenting as a pituitary mass. Clinical differentiation remains a challenge; often misdiagnosed preoperatively and the definitive diagnosis established only through postoperative histopathological examination.

Case: 51-year-old lady with a history of primary hypothyroidism (on stable dose of levothyroxine for >10 years), rheumatoid arthritis (no treatment), POF, and hypertension was admitted with a 4-month history of fatigue, low-mood, persistent headache, unintentional weight loss, abdominal pain, nausea, vomiting, decreased appetite and postural symptoms. Endoscopy and CT (abdomen/pelvis) performed prior to admission did not show any significant pathology. She was misdiagnosed as depression. Blood tests on admission interestingly revealed secondary hypothyroidism (TSH-0.04mU/l), low T3-<2pmol/l, T4-8.5pmol/l). Hence, a full pituitary profile was carried out. Random cortisol(<28nmol/l) and ACTH(3.5nmol/l) were low with inadequate short Synacthen test response (basal-cortisol <28, post-synacthen cortisol-117 nmol/l) and low prolactin (34 mU/l). Hydrocortisone was initiated immediately with subsequent increased dose of levothyroxine. MRI (pituitary) revealed a heterogeneously enhancing pituitary mass (1.3x1.6x1.3 cm), suggesting macroadenoma, which was not present previously on MRI performed 14-months ago for anosmia. Further discussion at the pituitary MDT suspected hypophysitis, due to a thickened pituitary stalk and hyper-enhancing lesion. Further testing for ACE and IgG was negative. Complete resolution of the pituitary mass on interval MRI scan 3 months later confirmed the suspected diagnosis of hypophysitis, without needing a biopsy for histopathological confirmation.

Conclusion: • Prompt recognition of shift from primary to secondary hypothyroidism led to the diagnosis of hypopituitarism accounting for her presenting symptoms, and subsequent pituitary imaging. • Although rare, hypophysitis should be considered as a differential diagnosis to avoid unnecessary surgery. • MDT plays a crucial role in case of diagnostic dilemma and interval imaging is highly recommended. • This case highlights the diagnostic challenge of distinguishing hypophysitis from macroadenoma clinically.