Endocrine Abstracts

Introduction: Men with prolactinoma often present with larger tumors than women. Whether giant prolactinomas (≥4 cm, GP) present differently and achieve the same outcomes as non-giant macroprolatinomas (1-3.9 cm, MP) or microprolactinomas (<1 cm, mP) is not clearly established.

Methods: We report retrospective data from a monocentric cohort of 129 men with prolactinoma and we compare baseline characteristics and treatment response in patients with different tumor sizes. We excluded patients with very small tumors (maximal diameter <5mm or PRL initially <45 mg/l).

Results: Among the 129 patients, 25 (19%) harbored a GP (median PRL 9270 mg/l; size range: 40-60 mm), 83 (64%) had MP (median PRL 776 µg/l; 10-39mm), and 20 (15%) had mP (median PRL 103 µg/l; 5-9.9mm). The mean age at presentation was similar in the three subgroups (41±17, 45±17 and 45±16 years in the mP, MP and GP groups, respectively; NS). BMI and testosterone levels also did not differ significantly between the groups. Mean testosterone concentration at diagnosis was 6.3, 6.2 and 4.7nmol/l for mP, MP and GP, respectively. Patients with GP and MP suffered from more visual field deficits (60% and 24% respectively) than those with mP (0%, P<0.001). The same was true for cavernous sinus invasion (P<0.001), ACTH deficit (P=0.036) and TSH deficit (P<0.001). However, the frequency of LH deficit was similar in the three groups (mP 94%, MP 82%, GP 96%, P=0.132). The prevalence of gynecomastia was significantly higher (P<0.01) in mP (68%) than in MP (25%) or GP men (16%), although the prevalence of decreased libido or erectile dysfunction was similar in all three groups. The need for surgery during follow-up was significantly more important in GP (44%) than MP (31%) or mP (5%, P=0.015). At last follow-up, normal prolactin was achieved in 80% of mP patients, 68% of MP patients, and in only 40% of GP patients (P=0.010). At last follow-up more patients in the GP (65%) and MP (38%) group suffered from persistent hypogonadism than mP patients (20%) (P=0.008). The same was true for TSH deficit (P<0.001) and ACTH deficit (P=0.067).

Conclusion: In men, 83% of prolactinomas at diagnosis reach a size of 1 cm or more and 19% reach or exceed 4 cm. Interestingly, patients with mP more often present with gynecomastia than those with MP or GP, despite similar age, BMI and testosterone levels, perhaps leading to earlier diagnosis. Endocrine outcomes and resistance to treatment worsen with increasing tumor diameter.