Bromocriptine (INN; trade names Parlodel, Cycloset), an ergoline derivative, is a dopamine agonist that is used in the treatment of pituitary tumors, Parkinson's disease (PD), hyperprolactinaemia, neuroleptic malignant syndrome, and type 2 diabetes.

Amenorrhea, female infertility, galactorrhea, hypogonadism, and acromegaly may all be caused by pituitary problems, such as hyperprolactinaemia, and therefore, these problems may be treated by this drug. Since the late 1980's it has been used, off-label, to reduce the symptoms of cocaine withdrawal . In 2009, bromocriptine mesylate was approved by the FDA for treatment of type 2 diabetes under the trade name Cycloset (VeroScience). It is currently unknown how this drug improves glycemic control, but it has been shown to reduce HbA1c by ~0.5 percentage points.

Bromocriptine is a potent agonist at dopamine D2 receptors and various serotonin receptors. It also inhibits the release of glutamate, by reversing the glutamate GLT1 transporter.

Most frequent side effects are nausea, orthostatic hypotension, headaches and vomiting through stimulation of the brainstem vomiting centre. Bromocriptine can cause worsening of liver problems. Vasospasms with serious consequences such as myocardial infarction and stroke have been reported in connection with the puerperium, appears to be extremely rare event. Peripheral vasospasm (of the fingers or toes) can cause Raynaud's Phenomenon. Bromocriptine use has been anecdotically associated with causing or worsening psychotic symptoms (its mechanism is in opposition of most antipsychotics, whose mechanisms generally block dopamine). Pulmonary fibrosis has been reported when bromocriptine was used in high doses for the treatment of Parkinson's disease.

Henry George Friesen, CC OM FRSC (born July 31, 1934) is a Canadian endocrinologist, a distinguished professor emeritus of the University of Manitoba and the discoverer of prolactin, a hormone which stimulates lactation in mammary glands.

Born in Morden, Manitoba, he obtained a Bachelor of Science in medicine and a medical degree from the University of Manitoba in 1958. From 1965 to 1973 he was at McGill University and from 1973 to 1992 he was a professor and head of the department of physiology and professor of medicine at the University of Manitoba.

His research on growth hormones in dwarf children helped in developing a therapy for the treatment of this problem. In addition his work with prolactin helped to develop the drug bromocriptine, used for the treatment of infertility.

From 1991 until 1999 he was president of the Medical Research Council of Canada and helped to transform it into the Canadian Institutes of Health Research. He was president of the National Cancer Institute of Canada and president of the Canadian Society for Clinical Investigation. He is the founding chair of Genome Canada.