What is Endocrinology?
'''Endocrinology''' studies the working of the [[endocrine system]] and [[hormones]].<ref>Nussey S. & Whitehead S. 2001. ''Endocrinology: an integrated approach''. Oxford: Bios Scientific. {{ISBN|1-85996-252-1}}</ref> It is the science of the endocrine system and hormones in a wide range of animals. Endocrinology is also a [[medical specialty]]. This means that when a doctor finishes studying medicine in general, they can choose endocrinology as the part of medicine they work in. The endocrine system consists of several [[glands]] in different parts of the body. They secrete hormones directly into the blood. Hormones have many different functions and modes of action. Hormones are active in [[metabolism]], [[growth hormone|growth]] and [[developmental biology|development]], [[tissue (biology)|tissue]] function, [[sleep]], [[digestion]], [[Respiration (physiology)|respiration]], [[excretion]], [[mood]], [[Stress (biology)|stress]], [[lactation]], [[movement]], [[reproduction]], and [[perception]]. Another field is behavioral endocrinology.<ref>Nelson R.J. 2005. ''An introduction to behavioral endocrinology''. 4th ed, Sinauer.</ref><ref>{{Cite web |url=http://idea.ucr.edu/documents/flash/introduction_to_behavioral_endocrinology/story.htm |title=Introduction to behavioral endocrinology |access-date=2015-04-21 |archive-date=2016-12-02 |archive-url=https://web.archive.org/web/20161202210204/http://idea.ucr.edu/documents/flash/introduction_to_behavioral_endocrinology/story.htm |url-status=dead }}</ref><ref>{{Cite web |url=http://www-rci.rutgers.edu/~jmstern/chapter1/index.htm |title=behavioral endocrinology |access-date=2015-04-21 |archive-date=2016-11-04 |archive-url=https://web.archive.org/web/20161104075936/http://www-rci.rutgers.edu/~jmstern/chapter1/index.htm |url-status=dead }}</ref> == Medical aspects == Medical understanding of hormones began in the 19th century with [[Graves' disease]], caused by a swelling of the thyroid gland. Since the mid-19th century many medical conditions have been found caused by ho