The endocrine system is composed of different glands that regulate hormones in the body. Hormones are chemicals that communicate to different cells to regulate body functions like growth and metabolism. Some organs that are part of the other systems in the body also act as endocrine organs. Examples of such organs are liver which secretes thrombopoietin and kidney which secrete renin.
Bones are made of hard materials that protect the internal organs and provide support to the body. In between the bones are the marrows where blood is produced. Recently, it was discovered that the bone is also an endocrine organ that helps regulate metabolism. Scientists looked into the bones' role in regulating blood sugar and lipid production. This is very important to people who have diabetes.
In an article in the 'Endocrine Society' journal in 2001, Dr. Gerard Karsenty wrote about how leptin, a hormone responsible for the production of fat cells, has a role in bone formation by inhibiting it through some signals from hypothalamus. Because of this findings, researchers together with Dr. Karsenty hypothesized that there must be some signals from the bones to the fat cells. Thus, in the research by scientists from the Columbia University Medical Center entitled “Endocrine Regulation of Energy Metabolism by the Skeleton”, experiments were conducted on mice. By genetically mutating mice, researchers were able to observe how osteocalcin affects pancreatic beta-cells, insulin and adiponectin. Osteoblasts that are needed in bone formation also produce a hormone called osteocalcin. Pancreatic beta cells produce the insulin which is the hormone responsible in controlling blood sugar. Adiponectin is another hormone that regulates lipids and glucose. Results of this research show that there is an increase insulin secretion and sensitivity which protected mice from developing diabetes. There is also an increase in insulin and adiponectin expression when the osteoblasts were co-cultured with adipocytes (fat cells). These results show the endocrine function of the bone.
This research has great impact on people with type-2 diabetes. Osteocalcin levels in people with diabetes are low. Thus, if osteocalcin can be injected to a person with diabetes, it might be a way to regulate the insulin levels. Further research is underway to find a solid link between osteocalcin and type-2 diabetes.
Because of this research, bones now have three important functions: support and structure, blood production and metabolism. Thus, it plays a role in the musculo-skeletal system, circulatory system and endocrine system.
Columbia University Medical Center (2007, August 10). Skeleton Is An Endocrine Organ, Crucial To Regulating Energy Metabolism.
ScienceDaily. Retrieved March 12, 2011, from http://www.sciencedaily.com /releases/2007/08/070809130039.htm