Endocrine Abstracts

Introduction: The data on giant prolactinomas (the rare (3%) subtype of lactotroph PitNET (≥40 mm) ), often causing clinical and therapeutic difficulties are scarce.

Aim: We studied clinical/biochemical and treatment outcomes differences between giant and macroprolactinomas.

Materials and methods: Consecutive patients with giant prolactinomas ≥40 mm (GP) and macroprolactinomas >10 mm<40 mm (MP) treated in the tertiary clinical center in 2022-2023 were included.

Results: There were 41 patients with macroprolactinomas: 15 GP (87% men) and 26 MP (65, 4% men). The age at the diagnosis was 41 in GP vs 48 in MP (P=0.265). In GP and MP groups the most frequent symptoms included headaches (10/66, 7% vs 15/57, 7%, P=0.640), vision disturbances (10/66, 7% vs 6/23, 1%, P=0.021) and hypogonadism (14/93, 3% vs 18/69, 2%, P=0.267). Hypogonadism, TSH and ACTH deficiency were significantly more frequent in patients with GP than MP (8/53, 3% vs 5/19, 2%, P=0.013). In GP group FSH concentration was markedly lower than in MP (average 1,12 ulU/ml vs 3,09 ulU/ml, P=0.005). The baseline prolactin levels were relevantly higher in GP than in MP group (172026 ulU/ml vs 14224 ulU/ml, P<0.001). The optic chiasm compression was more common in GP than in MP (12/80% vs 9/34, 6%, P=0.021, respectively). The apoplexy occurred only in two patients with GP. Cabergoline was the most common dopamine agonist administered in 24 cases of MP and 12 cases of GP (P=0.512). The surgery was performed in 4/26, 8% of GP vs 4/15, 2% of MP (P= 0.565). Among GP patients one underwent the surgery 2 times and another one 3 times. Other therapeutical options implemented only in GP subgroup included Lanterotide (two cases), with no biochemical and clinical effecty in one case Pasireotide with a remarkable analgetic effect. In one case of aggressive tumour Temozolomide was implemented with a disease stabilization. Cabergoline resistance was observed in 5/33% of GP vs 1/3, 85% of MP, P=0.327). The tumour decrease was observed in 11/73, 3% of GP and 13/50% of MP cases. The percentage of tumour shrinkage was significantly higher in patients with GP compared to MP (average 57% vs 32%, P=0.040).

Conclusions: The majority of GP and MP patients are men. Pituitary axis deficiencies and visual deficits occur more frequently in GP group. The incidence of tumour shrinkage is similar in GP and MP, however in GP the tumour decrease is higher. Cabergoline resistance and surgery procedures are more common in GP group. Further studies are needed to understand the biology and natural course of GP and MP.