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 our hospital with poorly controlled type 2 diabetes. Her HbA1c 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 United States, 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 90 % between 1 week before and after the initial administration of bromocriptine.