Endocrinology

Endocrinology studies the working of the endocrine system and hormones.
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 and development, tissue function, sleep, digestion, respiration, excretion, mood, stress, lactation, movement, reproduction, and perception. Another field is behavioral endocrinology.
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 hormone imbalance, that is, too much or too little of a hormone.
An endocrinologist can help people who have diseases related to their endocrine system. Diseases that an endocrinologist would treat include:
These are just examples; there are many other endocrine diseases.
An endocrinologist can find out if a person has one of these diseases by doing tests. They can test a person's blood to find out if they have too much or too little of a hormone. An example of this is Type 1 diabetes. People who have Type 1 diabetes do not have enough of a hormone called insulin. Endocrinologists usually do not treat patients directly, but give advice to physicians about what how patients might be helped.
Endocrine disorders fall into three groups: 
Most medical applications concern the lack of balance between hormones, and sometimes the complete lack of a necessary hormone. For example, most forms of hyperthyroidism are associated with an excess of thyroid hormone and a low level of thyroid stimulating hormone.
Helping transgender people.
Endocrinologists can advise on hormone treatment for transgender persons. A transgender person might want their body to look different so that they look more like their chosen gender. For example, a transgender woman might want less facial hair so that she looks less like a man to other people.
Related pages.
The main pages which explain endocrinology are: