Prolactin response to an acute bromocriptine suppression test (ABST) following surgical debulking of macroprolactinomas

Funding: None. Conflict of interest statement: The authors declare that they have no conflict of interest. Data Availability Statement: All relevant data are within the paper. Abstract Introduction: In centers with tight budgets treating macroprolactinomas with transsphenoidal surgery remains an appealing option because it may increase the efficacy of dopamine agonists (DA) postoperatively. The aim of our study was to determine whether surgical debulking of prolactinomas enhances the response to DA using the results of an acute bromocriptine suppression test (ABST) performed pre and post operatively. Methods: This retrospective case-control study included 12 patients with macroprolactinomas that underwent surgical debulking procedures (9 males; median age: 40 years). ABSTs were performed pre and postoperatively using the following protocol: 1) basal prolactin levels were measured through an indwelling cannula; 2) 2.5 mg of bromocriptine was administered; 3) prolactin levels were measured at hourly intervals for 5 hours after bromocriptine administration. Analyses were performed on log-transformed data. Results: Postoperatively, patients had lower prolactin during the ABST (mean difference-0.701, 95% CI -1.170 -.231, P=0.005), but without any difference in dynamics of prolactin decrease. Baseline prolactin levels correlated positively with prolactin levels at the end of the bromocriptine test. This was evident prior (ρ=0.715, P=0.009) and after surgery (ρ=0.909, P<0.001, P=0.009). Likewise, there was no correlation between baseline prolactin levels and absolute change in prolactin levels at the end of the bromocriptine test. Conclusion: Prolactin levels decreased significantly during the ABST both pre and postoperatively, but without any difference in dynamics of prolactin decrease. Although our results did not show that surgical debulking enhances the response to DA, further studies are required to determine whether absolute volume reduction affects this relationship. Lora Stanka Kirigin1, Mateja Strinović1, Gorana Mirošević1, Darko Stipić2, Vatroslav Čerina2, Jana Ježková 3, Ludmila Brunerova 4, Michal Kršek 4, Milan Vrkljan1