The endocrine system is made up of glands that make hormones. Hormones are the
body's chemical messengers. They carry information and instructions from one set of
cells to another.
The endocrine (pronounced: EN-duh-krin) system influences almost every cell, organ,
and function of our bodies.
What Does the Endocrine System Do?
Endocrine glands release
into the bloodstream. This lets the hormones travel to cells in other
parts of the body.
The endocrine hormones help control mood, growth and development, the way our
, and reproduction.
The endocrine system regulates how much of each hormone is released. This can
depend on levels of hormones already in the blood, or on levels of other substances
in the blood, like calcium. Many things affect hormone levels, such as stress, infection,
and changes in the balance of fluid and minerals in blood.
Too much or too little of any hormone can harm the body. Medicines can treat many
of these problems.
What Are the Parts of the Endocrine System?
While many parts of the body make hormones, the major glands that make up the endocrine
system are the:
The pancreas is part of the endocrine system and the digestive
system. That's because it secretes hormones into the bloodstream, and makes and
secretes enzymes into the digestive tract.
Hypothalamus: The hypothalamus (pronounced: hi-po-THAL-uh-mus)
is in the lower central part of the brain.
It links the endocrine system and nervous system. Nerve cells in the hypothalamus
make chemicals that control the release of hormones secreted from the pituitary gland.
The hypothalamus gathers information sensed by the brain (such as the surrounding
temperature, light exposure, and feelings) and sends it to the pituitary. This information
influences the hormones that the pituitary makes and releases.
Pituitary: The pituitary (pronounced: puh-TOO-uh-ter-ee) gland
is at the base of the brain, and is no bigger than a pea. Despite its small size,
the pituitary is often called the "master gland." The hormones it makes
control many other endocrine glands.
The pituitary gland makes many hormones, such as:
growth hormone, which stimulates the growth of bone and other body tissues and
plays a role in the body's handling of nutrients and minerals
prolactin (pronounced: pro-LAK-tin), which activates milk production in women
who are breastfeeding
thyrotropin (pronounced: thy-ruh-TRO-pin), which stimulates the thyroid gland
to make thyroid hormones
corticotropin (pronounced: kor-tih-ko-TRO-pin), which stimulates the adrenal gland
to make certain hormones
antidiuretic (pronounced: an-ty-dy-uh-REH-tik) hormone, which helps control body
water balance through its effect on the kidneys
oxytocin (pronounced: ahk-see-TOE-sin), which triggers the contractions of the
uterus that happen during labor
The pituitary also secretes endorphins (pronounced: en-DOR-fins), chemicals that
act on the nervous system and reduce feelings of pain. The pituitary also secretes
hormones that signal the reproductive organs to make sex hormones. The pituitary gland
and the menstrual cycle in women.
Thyroid: The thyroid (pronounced: THY-royd) is in the front part
of the lower neck. It's shaped like a bow tie or butterfly. It makes the thyroid hormones
thyroxine (pronounced: thy-RAHK-sin) and triiodothyronine (pronounced: try-eye-oh-doe-THY-ruh-neen).
These hormones control the rate at which cells burn fuels from food to make energy.
The more thyroid hormone there is in the bloodstream, the faster chemical reactions
happen in the body.
Thyroid hormones are important because they help kids' and teens' bones grow and
develop, and they also play a role in the development of the brain and nervous system.
Parathyroids: Attached to the thyroid are four tiny glands that
work together called the parathyroids (pronounced: par-uh-THY-roydz). They release
parathyroid hormone, which controls the level of calcium in the blood with the help
of calcitonin (pronounced: kal-suh-TOE-nin), which the thyroid makes.
Adrenal Glands: These two triangular adrenal (pronounced: uh-DREE-nul)
glands sit on top of each kidney. The adrenal glands have two parts, each of which
makes a set of hormones and has a different function:
The outer part is the adrenal cortex. It makes hormones called
corticosteroids (pronounced: kor-tih-ko-STER-oydz) that help control salt and water
balance in the body, the body's response to stress, metabolism, the immune
system, and sexual development and function.
The inner part is the adrenal medulla (pronounced: muh-DUH-luh).
It makes catecholamines (pronounced: kah-tuh-KO-luh-meenz), such as epinephrine (pronounced:
eh-puh-NEH-frun). Also called adrenaline, epinephrine increases blood pressure and
heart rate when the body is under stress.
Pineal: The pineal (pronounced: pih-NEE-ul) body, also called
the pineal gland, is in the middle of the brain. It secretes melatonin (pronounced:
meh-luh-TOE-nin), a hormone that may help regulate when you sleep at night and when
you wake in the morning.
Reproductive Glands: The gonads are the main source of sex hormones.
Most people don't realize it, but both guys and girls have gonads. In guys the male gonads, or testes (pronounced:
TES-teez), are in the scrotum. They secrete hormones called androgens (pronounced:
AN-druh-junz), the most important of which is
(pronounced: tess-TOSS-tuh-rone). These hormones tell a guy's body when
it's time to make the changes associated with puberty, like penis and height growth,
deepening voice, and growth in facial and pubic hair. Working with hormones from the
pituitary gland, testosterone also tells a guy's body when it's time to make sperm
in the testes.
A girl's gonads, the ovaries
(pronounced: OH-vuh-reez), are in her pelvis. They make eggs and secrete the female
(pronounced: ESS-truh-jen) and
(pronounced: pro-JESS-tuh-rone). Estrogen is involved when a girl starts
puberty. During puberty, a girl
will have breast growth, start to accumulate body fat around the hips and thighs,
and have a growth spurt. Estrogen and progesterone are also involved in the regulation
of a girl's menstrual cycle.
These hormones also play a role in pregnancy.
Pancreas: The pancreas (pronounced: PAN-kree-us) makes insulin
(pronounced: IN-suh-lin) and glucagon
(pronounced: GLOO-kuh-gawn), which are hormones that control the level of glucose,
or sugar, in the blood. Insulin helps keep the body supplied with stores of energy.
The body uses this stored energy for exercise and activity, and it also helps organs
work as they should.