MON-116 - Long-Term Biochemical and Radiologic Outcomes after Dopamine Agonist Therapy and Withdrawal in A Male Patient with Prolactinoma

Prolactinomas in men typically present with higher prolactin levels, larger tumor size, and a greater risk of mass effect compared with those in women. However, long-term outcomes and evidence-based criteria for dopamine agonist (DA) withdrawal in male patients remain poorly defined. We report a six-year biochemical, radiologic, and clinical follow-up of an adult male with prolactinoma treated with cabergoline, including outcomes following a structured DA discontinuation.
The patient initially presented in 2019 with galactorrhea, gynecomastia, and severe hyperprolactinemia (233.3 ng/mL). Pituitary magnetic resonance imaging (MRI) demonstrated a macroadenoma measuring 1.4 × 1.1 × 1.0 cm with cavernous sinus extension, without optic chiasm compression. Breast ultrasonography was unremarkable (BI-RADS 1), supporting an endocrine etiology. Cabergoline therapy resulted in a rapid biochemical response, with prolactin suppression to < 0.6 ng/mL within six months and marked tumor shrinkage to 10 × 6 × 7 mm by early 2020.
Over subsequent years, annual prolactin measurements remained persistently suppressed or within the low-normal range (approximately 1.0–3.9 ng/mL). Serial MRI studies demonstrated continued tumor regression and long-term stability of an 8–9 mm residual microadenoma, without suprasellar extension, optic pathway involvement, or progressive cavernous sinus encroachment. In the absence of hypopituitarism, visual compromise, or radiologic progression, a gradual DA taper was initiated in 2023, followed by complete discontinuation in 2025 after sustained biochemical and radiologic control.
Following DA withdrawal, prolactin levels initially remained within the normal range, measuring 1.24 ng/mL in July 2025. However, subsequent follow-up demonstrated biochemical recurrence, with prolactin rising to 11.32 ng/mL by October 2025. Repeat pituitary MRI obtained after DA discontinuation revealed interval growth of the residual adenoma, with an increase of approximately 3 mm in maximal diameter compared with prior imaging, indicating radiologic progression following therapy withdrawal.
This case highlights the complexity of DA discontinuation in male patients with prolactinoma and underscores the importance of cautious patient selection and close post-withdrawal surveillance. Although prolonged DA therapy achieved sustained biochemical control and significant tumor regression, measurable tumor regrowth after withdrawal emphasizes the need for individualized risk assessment and strict long-term biochemical and radiologic monitoring when considering therapy cessation.

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