Endocrinology is a branch of biology that studies hormones and their effects on the body. As practitioners of one of the medical specialties, physicians who are endocrinologists treat patients with disorders of the endocrine system. That part of the human body includes the glands, like the pituitary, pancreas, thyroid and adrenals, that produce hormones. Now the regulation of hormones within the body is a delicate balancing of many factors, and imbalances can have enormous consequences for health, growth, and even the acquisition of the characteristics (like having a beard or developing breast tissue) that are the outward manifestations of being a grown man or woman, that is, of biological gender. Endocrinology includes the study of both the normal processes that are directed by hormones, as well as the disease states, and unusual features, that are associated with the effects of hormonal imbalances.
"The term "endocrine" denotes internal secretion of biologically active substances—in contrast to "exocrine," which denotes secretion outside the body, eg, through sweat glands or ducts that lead into the gastrointestinal tract <ref>John D. Baxter, MD, Ralff C.J. Ribeiro, MD, PhD, Paul Webb, PhD Chapter 1. Introduction to Endocrinology in Basic and Clinical Endocrinology 7th Edition, Copyright © 2004 by The McGraw-Hill Companies<ref> So, the digestive enzymes produced by the pancreas that flow into the pancreatic duct to empty into the small intestine are not considered endocrine, but exocrine secretions. On the other hand, insulin, which is produced by the islet cells of the pancreas and secreted into the bloodstream, makes the pancreas a part of the endocrine system. Diabetes, a disease that can come about because of low insulin levels, is one of the more common problems treated by endocrinologists.
History of Endocrinology in modern medicine
When William Osler (1849–1919) one of the most preeminent Internal Medicine internists of the late 19th and early 20th centuries, wrote the first edition of his famous medical textbook:Principles and Practice of Medicine Designed for the Use of Practitioners and Students of Medicine. New York: D. Appleton and Co; 1892 , the specialty of endocrinology did not yet have a name. Despite that, there were known diseases of what were then called “ductless glands” such as the thyroid and adrenal glands. "Osler's text notes disorders such as exophthalmic goiter, myxoedema, and cretinism, known then to be related to one or another disease of the thyroid gland; the text also notes Addison's disease, an affliction of the adrenal glands. He lumped these glandular diseases into the same section of his book as blood diseases; the entire section on these glandular diseases is only 9 pages long (endocrine texts today can run to thousands of pages and several volumes) reference for quote:Clark T.Sawin MD: William Osler (1849–1919) and the Treatment of Addison's Disease [Historical Note] William Osler (1849-1919) and the Treatment of Addison's Disease. Endocrinologist. 14(2):51-53, March/April 2004.." It was Osler who first hit upon empiric treatments for Addison disease,administering in 1895, glycerine extract of porcine adrenal glands. In this, he copied the earlier success of George R. Murray (1865–1939), an English physician, who used a glycerine thyroid gland extract for treatment of the symptoms of severe hypothyroidism.