Rapid and dramatic glucose-lowering effect of bromocriptine in an inadequately controlled type 2 diabetes patient with prolactinoma.

Dopamine receptor agonists are typically used to treat Parkinson's disease and certain pituitary tumors, such as prolactinoma or a growth hormone-producing tumor. A 53-year-old woman with a history of prolactinoma was referred to Kumamoto University Hospital (Kumamoto, Japan) with poorly controlled type 2 diabetes. Her glycated hemoglobin and serum prolactin levels were increased (8.8% and 160.3 ng/mL, respectively). Bromocriptine, a dopamine D2 receptor agonist, was administered to reduce her serum prolactin level. Because bromocriptine-QR (quick release) has been approved for the treatment of type 2 diabetes mellitus in the USA, a continuous glucose monitoring system, FreeStyle Libre Pro, was utilized to examine the effect of bromocriptine on glycemic control. After the initial administration of bromocriptine, glucose levels were rapidly and dramatically ameliorated, and the time in range (70-180 mg/dL) improved from <50% to >90% between 1 week before and after the initial administration of bromocriptine.