The Endocrine System

The endocrine system is an intricate collection of hormone-producing glands scattered throughout the body. As an interrelated group, these glands influence almost every cell, organ, and function of our bodies, helping to control mood, metabolism, growth, tissue function, and sexual development.

Some glands have both endocrine and non-endocrine regions. For example, the pancreas secretes digestive enzymes as well as hormones. Some organs (such as the stomach, intestines, and heart) produce hormones even though their primary function is not hormone secretion.

Major Glands of the Endocrine System and What They Do

Adrenal (Suprarenal) Glands

• Location: Top of each kidney
• Hormones produced: Catecholamines (adrenaline or epinephrine); mineralocorticoids (like aldosterone); glucocorticoids (like cortisol); steroid hormones (like androgen)
• Function: Help control metabolism, kidney function, blood pressure, cardiovascular function, the body's response to stress, the immune system, and sexual development and function. Help balance the effects of insulin in breaking down sugar for energy.

Gonads

• Location:
  • Female ovaries—On each side of the uterus
  • Male testes—In the scrotum
• Hormones produced:
  • Ovaries—Estrogen and progesterone
  • Testes—Androgens (testosterone)
• Function: regulate puberty and fertility
  • Ovaries—Induce female sexual characteristics such as breast growth, the accumulation of body fat around the hips and thighs, and the growth spurt that occurs during puberty. Both estrogen and progesterone are also involved in regulating the menstrual cycle and pregnancy.
  • Testes—Induce male sexual characteristics such as maturation of the penis, deepening of the voice, development of muscles, increase in facial and body hair and the growth spurt that occurs during puberty. They also regulate sex drive and are involved in production of sperm cells.

Hypothalamus

• Location: Lower central part of the brain
• Hormones produced: Releasing hormones for the pituitary gland
• Function: Stimulates or suppresses the release of hormones in the pituitary gland to control water balance, sleep, temperature, appetite and blood pressure. Serves as the primary link between the endocrine and nervous systems.

Pancreas

• Location: Behind the stomach
• Hormones produced: Insulin, gastrin, glucagon, somatostatin
• Function: Regulates the level of sugar in the bloodstream and keeps the muscles supplied with glucose

Parathyroid Glands

• Location: Above and below the thyroid
• Hormones produced: Parathyroid hormone
• Function: Regulate calcium and phosphorous concentrations in the bloodstream

Pineal Gland

• Location: Middle of the brain
• Hormones produced: Melatonin
• Function: Helps regulate the wake-sleep cycle

Pituitary Gland

• Location: Base of the brain under the hypothalamus
• Hormones produced: Adrenocotropic hormone (ACTH), antidiuretic hormone, corticotropin, luteinizing hormone (LH), follicle stimulating hormone (FSH), human growth hormone (hGH), oxytocin, prolactin, thyrotropin
• Function: Controls the activity of many other endocrine glands (thyroid, ovaries, adrenal). Helps with functions such as the growth of long bones, muscles, and viscera; body water balance; utilization of nutrients and minerals; sensitivity to pain. In females, it helps stimulate egg production, prepares the uterus for pregnancy, triggers contractions that occur during labor, activates milk production for breastfeeding. In men, it helps to stimulates sperm production.

Thyroid Gland

• Location: Front portion of the lower neck
• Hormones produced: Thyroxine, triiodothyronine, calcitonin
• Function: Helps to regulate metabolism (including weight control and energy levels), the body's calcium balance, muscle strength, emotions, the ability to tolerate heat or cold, and the development of the brain and nervous system in children

Thymus Gland

• Location: In the chest just under the breastbone
• Hormones produced: Thymosin
• Function: Development of the body's immune system