Late presentation of acromegaly in medically controlled prolactinoma patients

Co-secretion of growth hormone (GH) and prolactin (PRL) from a single pituitary adenoma is common. In fact, up to 25% of patients with acromegaly may have PRL co-secretion. The prevalence of acromegaly among patients with a newly diagnosed prolactinoma is unknown. Given the possibility of mixed GH and PRL co-secretion, the current recommendation is to obtain an insulin-like growth factor-1 (IGF-1) in patients with prolactinoma at the initial diagnosis. Long-term follow-up of IGF-1 is not routinely done. Here, we report two cases of well-controlled prolactinoma on dopamine agonists with the development of acromegaly 10-20 years after the initial diagnoses. In both patients, a mixed PRL/GH-cosecreting adenoma was confirmed on the pathology examination after transsphenoidal surgery (TSS). Therefore, periodic routine measurements of IGF-1 should be considered regardless of the duration and biochemical control of prolactinoma. LEARNING POINTS Acromegaly can develop in patients with well-controlled prolactinoma on dopamine agonists.The interval between prolactinoma and acromegaly diagnoses can be several decades.Periodic screening of patients with prolactinoma for growth hormone excess should be considered and can 
lead to an early diagnosis of acromegaly before the development of complications.