Pulmonary Fibrosis in a Patient With a Prolactinoma on Dopamine Agonists: Coincidence or Consequence

Prolactinomas are the most common functional pituitary tumor and are typically managed with dopamine agonists such as bromocriptine or cabergoline. Although these agents are generally well tolerated and effective in reducing prolactin levels and often tumor size, they have been implicated in rare but serious fibrotic complications, including interstitial lung disease (ILD). We describe a 65-year-old man with a longstanding prolactinoma who received cumulative high-dose bromocriptine and cabergoline therapy over several decades. Despite initial tumor shrinkage and partial biochemical control of hyperprolactinemia with dopamine agonists, stereotactic radiosurgery, and transsphenoidal surgery, the patient developed progressive exertional dyspnea and cough, accompanied by imaging and histopathological findings consistent with "usual interstitial pneumonia" (UIP). Autoimmune and environmental causes were largely excluded, suggesting a drug-induced etiology. Following discontinuation of cabergoline, the patient has been on continued surveillance of his prolactin levels and tumor status, with symptomatic treatment of his UIP. This case underscores the potential for dopamine agonist-associated ILD, even in patients with prolactinomas who generally receive lower weekly doses than those used in Parkinson's and related diseases. Early recognition of respiratory symptoms, pulmonary function, and radiological investigations are indicated in selected symptomatic cases.