Mexican and German scientists from the Institute of Neurobiology at the National University of Mexico (UNAM) and the General Hospital and Paracelsus Medical University Nuremberg analyzed and interpreted studies about prolactin and metabolic health and proposed a new classification for prolactin levels measured in patients which they call the “metabolic classification of prolactin levels”.
Prolactin, the pituitary hormone fundamental for lactation and colloquially referred to as the “nursing hormone”, was long believed to be diabetogenic. The view that prolactin, and all other anterior pituitary hormones, are diabetogenic was first posed by the Argentinian physiologist Bernardo Houssay, who was awarded the Nobel Prize for Physiology and Medicine in 1947 for his work on this subject.
The view that prolactin is diabetogenic and that high levels of prolactin are detrimental for metabolic health persisted until recently. Indeed, excessively high circulating prolactin levels in patients with a prolactin-producing pituitary adenoma, for example, but also very low prolactin levels, are associated with weight gain, obesity, metabolic syndrome, and type 2 diabetes. However, there is a window of prolactin levels in the high-normal and hyperprolactinemic range associated with metabolic health. This is shown by multiple epidemiologic studies and is supported by experimental models for obesity, insulin resistance, and diabetes in animals.
Mexican and German scientists from the Institute of Neurobiology at the National University of Mexico (UNAM) and the General Hospital and Paracelsus Medical University Nuremberg analyzed and interpreted these studies and proposed a new classification for prolactin levels measured in patients which they call the “metabolic classification of prolactin levels”.
After a comprehensive review of the field, circulating prolactin levels were identified that influence the metabolic outcome and their consideration recommended for clinical studies addressing prolactin levels and metabolic diseases, such as type 2 diabetes. It is argued, that PRL levels in the high-normal and hyperprolactinemic range (up to 100 µg/L) could not only be associated with metabolic health but are required to maintain metabolic homeostasis and to counteract the development of type 2 diabetes.
“Patients with high prolactin levels are often excluded from studies investigating the role of prolactin in diabetes” says Dr. Jakob Triebel, one of the authors of the study, “where precisely these patients should undergo further investigation”. “Excluding patients with high prolactin levels from studies constitutes a selection bias and should be avoided”, explains Dr. Triebel.
According to the authors, outstanding questions arising from the study include the identification of unknown factors responsible for decreased prolactin levels in patients with metabolic diseases, as well as the discovery of mechanisms regulating prolactin levels in patients maintaining a metabolically healthy state.
The study appears in the Journal “Trends in Endocrinology and Metabolism”, was published online on February 7th.
Yazmín Macotela Ph.D.
Instituto de Neurobiología
Universidad Nacional Autónoma de México (UNAM)
Queretaro, Mexico 76230
Email: macotelag@unam.mx
Jakob Triebel M.D.
Institute for Clinical Chemistry, Laboratory Medicine and Transfusion Medicine
Head: Prof. Dr. Thomas Bertsch
General Hospital and Paracelsus Medical University Nuremberg
90419 Nuremberg
Germany
Email: Jakob.Triebel@gmx.de
Website: http://jakobtriebel.de
Carmen Clapp Ph.D.
Instituto de Neurobiología
Universidad Nacional Autónoma de México (UNAM)
Queretaro, Mexico 76230
Email: clapp@unam.mx
Website: http://personal.inb.unam.mx/clapp/
https://www.sciencedirect.com/science/article/abs/pii/S1043276020300047
10.1016/j.tem.2020.01.004
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