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The diagnosis of pituitary microprolactinomas is often obscured by relatively low levels of elevated prolactin compared to macroprolactinomas. This may lead to varying patterns of medical therapy versus observation. We sought to correlate prolactin levels in suspected microprolactinomas with tumor volumes and clinical outcomes. This was a multicenter retrospective study of patients with pituitary microadenomas with baseline prolactin levels > 18ng/ml for males and > 30ng/ml for females. A linear-mixed model was used to depict changes in tumor volume over time. There were 65 patients with a mean tumor volume of 95.9mm 3 and mean prolactin level of 59.4ng/ml. There were significantly higher prolactin levels in patients with tumors above the mean volume versus below (74.0 versus 53.4ng/ml, p = 0.027). 26 patients were observed, 31 were treated with anti-dopaminergic therapy, and 8 had surgery. There were significantly greater baseline prolactin levels for patients who were treated surgically (mean 86.4ng/ml) than those treated medically (mean 61.7 g/ml) or observed (mean 48.5ng/ml) (p = 0.02). Among the 26 patients who were surveilled, 13 patients demonstrated spontaneous tumor shrinkage, 12 remained stable, and 1 patient's tumor grew but was lost to follow-up. Linear mixed modeling demonstrated a statistically significant rate of tumor shrinkage over time of 3.67mm 3 /year (p = 0.03). When analyzing patients who were observed versus those requiring surgery after initially being surveilled, there were significantly greater baseline PRL/volume ratios in surgical patients versus those observed (8.1 ng/ml/mm 3 versus 2.4 ng/ml/mm 3 , p = 0.025). Suspected microprolactinomas may demonstrate more convincingly elevated prolactin levels when measuring over 95.9mm 3 . Tumors with baseline prolactin levels over 50ng/ml may be more inclined to undergo medical treatment. In tumors with levels below 50ng/ml, it may be reasonable to undergo surveillance as these tumors tend to spontaneously shrink over time. In tumors that are surveilled, an elevated baseline PRL/volume ratio of > 8 ng/ml/mm 3 may be indicate serial tumor growth that may necessitate medical and/or surgical intervention., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Introduction: Prolactinoma account to the most common pituitary adenomas and current therapy regime constitutes of dopamine agonist therapy (DA) and surgery in selected cases [17]. Due to tumor fibrosis induced by previous DA therapy, surgical removal can be challenging though. Therefore, this study investigates how preoperative DA usage influences perioperative treatment and surgical outcome in prolactinoma and aims to ascertain whether a specific subgroup of prolactinoma patients could derive greater benefit from exclusive surgical intervention., Methods: We retrospectively analyzed n = 159 surgically treated and histologically confirmed prolactinomas in the sella region from 2013-2022 in our institution. Clinical, radiological and surgical features were analyzed. Univariate and multivariate analyses were performed., Results: Out of total of 159 prolactinoma patients, 83.6% received previous treatment with DA followed by surgery, while only 16.4% received exclusive surgery. Both groups presented similar initial tumor volumes (1.9cm 3 vs. 1.5cm 3 , p = 0.59) and equal preoperative prolactin levels (PRL) (199.7 µg/l vs. 191.0 µg/l, p = 0.44). Surgical procedures took significantly longer when patients received prior DA treatment (79 min. vs. 70 min., p = 0.0479). Six months after surgery, pretreated patients revealed significantly higher PRL compared to non-treated (107 g/l vs. 8.64 µg/, p = 0.0009). Additionally, untreated microprolactinoma presented a remission of 100%, whereas pretreated exhibited a remission rate of 88.75%., Conclusion: The current study demonstrates that prior DA treatment is associated with significantly longer surgeries, higher recurrence rates and lower rates of normalization of PRL levels after surgery, particularly in microprolactinomas and support the latest recommendations of the Pituitary Society's Consensus Statement 2023, which favors the option of surgery alone as first-line therapy for microprolactinomas., (© 2024. The Author(s).)