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The endocrine system is a network of glands that produce and secrete hormones involved in controlling many functions of the body. This includes growth and development, stability of internal bodily systems (homeostasis), metabolism and sexual function.

Glands and hormones are the primary features of the endocrine system. Glands are collections of cells that produce and secrete hormones. Hormones act as chemical messengers in the body, moving information and instructions from one group of cells to another by traveling through the blood.

The major glands of the endocrine system include:

• Pituitary gland. Located at the base of the brain, this “master gland” controls and regulates most of the functions of the other endocrine system glands.
  
  
• Hypothalamus. Located in the lower central part of the brain just above the pituitary gland. It regulates bodily systems such as breathing, hunger, thirst and temperature.
  
  
• Adrenal glands. Two triangular-shaped glands located above each kidney that are responsible for controlling a host of functions, including regulation of salt and water balance in the body. They also are partly responsible for controlling blood pressure.
  
  
• Thyroid gland. A small gland located in the lower front part of the throat, that produces thyroid hormones that regulate the body’s metabolism, weight, bone growth and development of the brain and nervous system.
  
  
• Parathyroid glands. Two pairs of tiny glands located behind the thyroid gland that are essential to regulate the balance of calcium in the body.
  
  
• Pancreas. Located behind the stomach, the pancreas serves two functions: digestive (exocrine) and hormonal (endocrine). The hormones it makes include insulin and glucagon.
  

  

• Pineal body. Located in the base of the brain, it is involved in regulating the body’s wake-sleep cycle.
  
  
• Thymus. Located in children in the chest above and in front of the heart, this gland is present in infancy and early childhood and provides immune system functioning for the growing child.
  
  
• Gonads. Located in the lower portion of the trunk of the body, the reproductive organs produce steroid hormones specific to the sexual characteristics and reproductive functions of males and females beginning at puberty.

Each of the endocrine glands produces certain types of hormones used by the body. The release of these hormones causes specific reactions to occur in the body. For example, the hypothalamus produces hormones such as growth hormone-releasing hormone (GHRH) and the pituitary gland produces hormones including prolactin and endorphins.