Bone functions as a novel endocrine organ in energy metabolism

The classic endocrine concept is a matter of dispute. The term "endocrine" denotes internal secretion of bioactive substances,in contrast to "exocrine," which denotes secretion outside the body.Traditionally,the endocrine organs refer to classic organs,such as the thyroid,gonadal,or adrenal glands;however,some non-classic endocrine organs have been shown to have endocrine functions.For example,fat is thought to be inert;the main function of fat is to provide protection for the internal organs and store energy.In 1994,leptin was reported to be secreted from adipocytes.Since then, additional adipokines and factors,such as adiponectin,