OR25-06 Pituitary gigantism: how much different from acromegaly? A comparison of clinical features and mortality in 3244 Patients

Abstract Disclosure: S. Kaniuka-Jakubowska: None. M. Kaszubowski: None. J. Davis: None. D. Abeyaratne: None. S.A. Akker: None. N. Archer: None. J. Ayuk: Ipsen. W. Drake: None. A. Grossman: None. M. Gurnell: Ipsen, Pfizer, Inc., Recordati. C.E. Higham: None. S.J. Hunter: None. D. Iacovazzo: None. N. Karavitaki: None. T. Kearney: None. P.B. Loughrey: Esteve, Recordati. R.D. Murray: Pfizer, Inc., Ipsen, Sandoz. A. Pal: None. Z. Plummer: None. P. Abraham: Pfizer, Inc., Recordati, HRA Pharmaceuticals, Pharmanovia. Y.H. Mamoojee: None. J.A. Wass: None. M. Korbonits: Ipsen, Sandoz, Novo Nordisk, Pfizer, Inc., Corcept, ONO. Background: Pituitary gigantism has rarely been studied in appropriate numbers due to its rarity. The aim of this study was to evaluate patients with pituitary gigantism, compare them to patients with acromegaly and assess their mortality. Methods: The pituitary gigantism group (PGG, n=290, from the UK Acromegaly Register (UKAR) and the International Familial Isolated Pituitary Adenoma Consortium) was compared to UKAR patients with acromegaly (acromegaly group, AG, n=2,954). Data collection period: 1936 to 2017. Findings: Patients with pituitary gigantism represent 7.8% of growth hormone (GH)-excess patients. We found male predominance in PGG (61% vs. 50% in AG). Males in PGG present their first symptoms (22.6 vs 27.7 yr) and diagnosis (26.9 vs 31.0 yr) earlier than females, resulting in greater final height (3.1 vs 2.6 SD). From the genetically-tested PGG patients, 41.7% harboured an AIP mutation. No clinical differences were observed in the disease course and treatment between AIP mutation positive vs AIP/GPR101 mutation negative patients. PGG patients presented more aggressive features expressed by a higher prevalence of macroadenomas (75.9% vs. 69.2%), extrasellar extension (46.8% vs 33.9%), more surgical interventions (88.9% vs 83.7%), repeat surgery (23.3% vs 8.4%), and transcranial surgery (12.6% vs 5.0%), and more axis deficiencies per patient (1.5 vs 1.0) at post-treatment assessment. Disease control was achieved with the same frequency in PGG and AG patients; however, the time from diagnosis to disease control was longer in PGG. PGG have a shorter life expectancy compared to patients with acromegaly (65.0 vs 73.6 yr). Mortality in PGG is significantly higher compared to AG (adjusted hazard ratio 2.09, 95% CI 1.46-3.04) and twice as high as in the general population (standardised mortality ratio 1.94 vs 1.53). Summary: This large GH excess patient group with long follow-up provided a unique opportunity to assess mortality rates. PGG have decreased survival not only compared to the general population but even in comparison with adult-onset patients. They present a more aggressive disease course needing more treatment modalities, with a greater burden of hypopituitarism. They have more treatment interventions and take longer to achieve biochemical disease control compared to acromegaly. These data emphasise that early diagnosis and aggressive treatment are critical on reducing morbidity and improving survival in patients with pituitary gigantism. Presentation: Monday, July 14, 2025