Background: Dopamine agonists (DAs) remain the first-line treatment for prolactinoma. However, some patients may develop resistance or intolerance to DAs. Orthostatic hypotension (OH) is a common side effect of DA therapy but the literature documenting and reporting on OH in the treatment of prolactinoma is scarce. Because the prevalence of orthostatic hypotension increases with advancing age, clinicians should pay more attention to elderly prolactinoma patients, who are treated with DAs. We aim to attract attention to orthostatic hypotension following cabergoline therapy for prolactinoma.

Case Presentation: A 68-year-old man was admitted to West China Hospital because of a pituitary tumor in the sella region for more than 8 years, and feeling nauseous and weak for more than six months. In 2016, the patient complained of fatigue and was later diagnosed with a pituitary tumor measuring 3.1x1.9x2.1cm in the sella, and PO Bromocriptine 2.5mg 6 tabs QD was taken regularly until 2021. Later, it was switched to cabergoline due to failure to achieve normoprolactinemia, and he had taken the drug regularly to the date of admission: October 2024. The most recent dose of cabergoline he had taken was 0.5mg three times a week (Monday, Wednesday, and Friday). From September 2020 to July 2024, the patient's prolactin ranged from 185ng/ml to 232ng/ml (RR: 4.6- 21.4ng/ml). Since April 2024, the patient has frequently experienced nausea, fatigue, or weakness, accompanied by dizziness, sweating, and palpitations, especially in the morning and after eating. The symptoms were relieved after lying down and resting. The bedside standing test was conducted during admission, and his supine blood pressure of 156/101 mmHg dropped to 122/98 mmHg, while his heart rate increased from 73 bpm to 81 bpm within 3 minutes of standing. Orthostatic hypotension due to the dopamine agonist was considered very likely, and Cabergoline therapy was stopped.

Analysis of the pituitary MRI imaging revealed that complete resection of the mass was not achievable through surgical intervention. Therefore, as per MDT’s recommendation and the patient’s preference, Gamma knife radiosurgery was performed with 24Gy at the 50% isodose line. The patient’s symptoms improved, and his serum prolactin level decreased.

We report a case that did not fully respond to the DAs and exhibited a series of DA-induced side effects, and discussed the pathophysiology of DA-induced OH, management strategies, alternative therapies, and potential treatment options for patients with DA intolerance.