Endocrine System: Function, Hormones, and Diseases

Part II: The Endocrine System

Endocrine System Function

The endocrine, or hormonal, system is another system of coordination within the body. This system is closely related to the nervous system, and they are dependent on each other. In some cases, the nervous system stimulates or inhibits the secretion of hormones, and in others, the hormones stimulate or inhibit the action of the nervous system.

The endocrine system consists of a series of glands located throughout the body. These glands, called endocrine glands, are not anatomically connected to each other. They pour their secretions directly into the bloodstream.

Endocrine glands are formed by specialized secretory cells that synthesize chemicals called hormones. Once produced, hormones are discharged into the blood and transported to all parts of the body through blood vessels. However, they only exert their action on certain cells or organs, called target cells or target organs.

Hormones are "chemical messengers" that have the following characteristics:

• They perform their function at a distance from where they have been synthesized.
• The reactions are slow but more durable.
• They work in very small quantities.

Hormonal System Operation

Endocrine glands do not secrete hormones continuously. There is a mechanism that regulates their production. Usually, it is the proper amount of hormone in the blood or the actions of this hormone that disrupts the release. This regulatory mechanism is called negative feedback and is controlled by the Central Nervous System. This helps maintain adequate levels of hormones in the blood for the duration of the stimulus that caused the discharge.

Endocrine Diseases

The main conditions associated with the endocrine system are:

• Diabetes: A chronic, incurable disease due to a shortage or lack of insulin, causing blood sugar to remain in excess of normal levels. There are several types, most notably:
  • Type 1 (insulin-dependent), in which no insulin is produced.
  • Type 2 (non-insulin-dependent), in which cells are unable to utilize insulin effectively.
• Thyroid disease: Hyperthyroidism and hypothyroidism are due to alterations in thyroid hormone production. In the first case, the metabolic activity of the individual increases, and in the second, the reverse is true.
• Pituitary dwarfism and gigantism: Caused by problems in the production of growth hormone during the developmental period.