Metabolic Syndrome in Hyperprolactinemia.

The metabolic syndrome (MetS) is a conglomerate of clinical findings that convey into increased morbidity and mortality from type 2 diabetes mellitus (T2D) and cardiovascular disease. Hyperprolactinemia (hyperPRL) is associated with components of MetS, especially during pregnancy. Endogenous levels of sex steroids are high during pregnancy in contrast to untreated or replaced hypogonadism in most patients with a prolactinoma and hypogonadism may confer increased risk of MetS in hyperPRL. Dopamine-D2-agonist therapy can improve MetS in patients with a prolactinoma and lower glucose levels in patients with T2D. HyperPRL is a biomarker for decreased dopaminergic tonus in the hypothalamic-pituitary circuit. Patients with a prolactinoma, patients with schizophrenia and/or T2D often have disturbances in this balance and the finding of lower prolactin (PRL) levels in polycystic ovary syndrome (PCOS) may indicate increased dopaminergic tonus. Recent studies supported that PRL levels within or above reference range may be differently related to MetS. In healthy study populations and in PCOS, PRL levels were inversely associated with metabolic risk markers. Ongoing research on PRL fragments, vasoinhibins, may help explain some of the contradicting findings between prolactin levels and metabolism. Improved knowledge about MetS in hyperPRL can characterize subgroups of patients with hyperPRL, who would not otherwise be considered as candidates for dopamine-D2-agonist therapy such as patients with postpartum cardiomyopathy and postmenopausal women with T2D.