When a doctor tries to figure out the cause of a disease, they are actually trying to figure out the etiology of the disease. Etiology is the cause of a disease or the science that deals with such causes. The word etiology comes from the Greek etio-, which means 'causation' and -ology, which refers to the scientific study of something.
You might be familiar with similar terms such as biology and geology. These words also refer to the scientific study of something. Biology is the study of life (bio) and geology is the study of the earth or rocks (geo).
A disease's etiology, or cause, generally falls into three main categories; intrinsic, extrinsic and idiopathic.
First we will talk about intrinsic etiologies. Intrinsic means coming from within. Therefore, any pathological, or disease-causing, change that has occurred from inside the body has occurred as a result of intrinsic factors.
The following are examples of intrinsic factors:
- Inherited conditions, or conditions that are passed down to you from your parents. An example of this is hemophilia, a disorder that leads to excessive bleeding.
- Metabolic and endocrine, or hormone, disorders. These are abnormalities in the chemical signaling and interaction in the body. For example, Diabetes mellitus is an endocrine disease that causes high blood sugar.
- Neoplastic disorders or cancer where the cells of the body grow out of control.
- Problems with immunity, such as allergies, which are an overreaction of the immune system..
The second category of disease etiology is extrinsic etiologies. This means the cause of the disease, or pathological change, came from outside of the body.
The following are examples of extrinsic factors:
- Infectious agents like bacteria, viruses, fungi, and parasites
- Animal bites or stings
- Chemicals, electricity, and radiation
Journal of Infectious Diseases and Diagnosis