The endocrine system consists of several glands, all in different parts of the body, that secrete hormones directly into the blood rather than into a duct system. Therefore, endocrine glands
are regarded as ductless glands. Hormones have many different functions
and modes of action; one hormone may have several effects on different
target organs, and, conversely, one target organ may be affected by more
than one hormone.
Endocrinology is the study of the endocrine system in the human body.This is a system of glands
which secrete hormones. Hormones are chemicals that affect the actions
of different organ systems in the body. Examples include
thyroid hormone, growth hormone, and insulin. The endocrine system involves a number of feedback mechanisms, so that often one hormone will control the action or release of another secondary hormone. If there is too much of the secondary hormone, it may provide negative feedback to the primary hormone, maintaining homeostasis.
Although every organ system secretes and responds to hormones, the clinical specialty of endocrinology focuses primarily on the endocrine organs, meaning the organs whose primary function is hormone secretion. These organs include the pituitary, thyroid, adrenals, ovaries, testes, and pancreas.
Endocrinology also involves the study of the diseases of the endocrine
system. These diseases may relate to too little or too much secretion of
a hormone, too little or too much action of a hormone, or problems with
receiving the hormone.
Endocrine disorders may be subdivided into three category:
Endocrine gland hyposecretion (leading to hormone deficiency)
Endocrine gland hypersecretion (leading to hormone excess)
Tumours (benign or malignant) of endocrine glands
Endocrine disorders are often quite complex, involving a mixed picture
of hyposecretion and hypersecretion because of the feedback mechanisms
involved in the endocrine system.
Diabetes is due to either the pancreas not producing enough insulin, or the cells of the body not responding properly to the insulin produced. There are three main types of diabetes mellitus:
Type 1 diabetes results from failure of the pancreas to produce enough insulin due to loss of beta cells. This form was previously referred to as "insulin-dependent diabetes mellitus" (IDDM) or "juvenile diabetes".The loss of beta cells is caused by an autoimmune response.The cause of this autoimmune response is unknown.
Type 2 diabetes begins with insulin resistance, a condition in which cells fail to respond to insulin properly.As the disease progresses, a lack of insulin may also develop. This form was previously referred to as "non insulin-dependent diabetes mellitus" (NIDDM) or "adult-onset diabetes". The most common cause is a combination of excessive body weight and insufficient exercise.