Endocrine system helps in the regulation and
coordination of body and body activities .
The endocrine system and nervous system work
Reacting to fear, growing taller, and developing male or
female characteristics are all activities in the body that
are partially regulated by hormones.
Hormones are substances secreted (released) by cells
that act to regulate the activity of other cells in the
Hormones act as chemical messengers, carrying
instructions that cause cells to change their activities.
Hormones act on a specific tissue called target tissue.
The processes in the body that
are regulated by hormones
Maintenance of homeostasis
Glands are organs of endocrine system specialized
for secretion of substances like hormones.
Some glands secrete their secretions into some
organs by ducts, they are called EXOCRINE
Other glands release their secretion directly into
the bloodstream that called ENDOCRINE GLANDS.
Some glands secrete their secretions both into
bloodstream and body organs, they are called as
Types of hormones
Proteinic Hormones consist of chain
of amino acids or related compounds.
Steroid Hormones are lipid like,
carbon ring compounds that are
chemically similar to cholesterol and
Regulation of hormone
The rate of hormone secretion varies with the needs
of the body.
In many cases the level of a hormone in the blood
turns production of the hormone off and on through
If high levels of a hormone stimulate the output of
even more hormone, the regulation is called positive
In negative feedback, the production of some
hormone or substance stops the production of another
The hypothalamus is the area of the brain
that coordinates the activities of the
nervous and endocrine systems. It
controls many body functions, including
body temperature, blood pressure, and
The hypothalamus receives information
about external and internal conditions
from other brain regions. The
hypothalamus responds by giving
instructions—in the form of hormones—to
the pituitary gland.
Hormones of Hypothalamus
Growth Hormone Releasing Hormone
(GRH or GH)
Adrenocorticotropic Hormone Releasing
Hormone (CRH or ACTH)
Thyroid Releasing Hormone (TRH or TSH)
Gonadotropic Releasing Hormone GnRH
(LH – FSH – LTH – RH)
The pituitary gland is an endocrine gland suspended
from the hypothalamus by a short stalk.
The pituitary gland secretes many hormones, including
some that control endocrine glands elsewhere in the
MSH (Melanin Stimulating Hormone)
ADH (Antiduretic Hormone)
These hormones stimulate the secretions of
Thyroid Stimulating Hormone (TSH): Thyroid
Adrenocorticotropic Hormone (ACTH): adrenal
Gonadotropic Hormones (LH, FSH, GTH): glands
of the reproductive system.
Follicle Stimulating Hormone (FSH): Growth and
maturation of the egg in the follicle.
In the testes, it stimulates the production of
Other name SOMATOTROPIN
A deficiency in this hormone will
result in a condition known as
An excess amount of this hormone
causes an abnormal increase in the
length. This condition is known as
MSH (Melanin Stimulating Hormone) It
stimulates production of melanocytes
MSH determines the color of the skin.
ADH (Vasopressin): Its main function is to
regulate the water balance of the body by
controlling reabsorption of water in the kidneys.
OXYTOCIN: This hormone stimulates the
smooth muscle fibers of the uterus to contract
It causes contractions of the channel cells of
the mammary glands so that milk can be
Thyroid and parathyroid gland
The thyroid gland,
located in the neck, is
wrapped around the
The parathyroid glands
are located on the back
of the thyroid gland.
Thyroid hormone thyroxin which has iodine in
Thyroid hormones regulate the body’s
metabolic rate and promote normal growth of
the brain, bones, and muscles during childhood.
Thyroid hormones also affect reproductive
functions and maintain mental alertness in
A high level of calcium in the blood stimulates the
thyroid gland to produce a hormone called
calcitonin. Calcitonin causes calcium to be
deposited in bone tissue rapidly, lowering the
Parathyroid hormone (PTH) or parathormone
released by parathyroid gland.
PTH is made and released in response to a falling
level of calcium in the blood in order to increase it.
Thyroid gland disorders
The underproduction of thyroid hormones is hypothyroidism.
The overproduction of thyroid hormones is hyperthyroidism.
The pancreas contains clusters of specialized cells,
called the islets of Langerhans. Two hormones made by
the islet cells that interact to control the level of
glucose in the blood.
Insulin, produced by β cells, is a hormone that
lowers blood glucose level by promoting the
accumulation of glycogen (glucose) in the liver. The
deficiency of insulin is known as diabetes mellitus.
Glucagon, produced by α cells, has the
opposite effect of insulin—it raises blood glucose levels.
Diabetes mellitus (2 TYPES) is a serious disorder in
which cells are unable to obtain glucose from the
blood, resulting in high blood glucose levels.
The kidneys excrete the excess glucose, and water
follows, resulting in excessive volumes of urine
and persistent thirst.
Because cells cannot take up glucose, they use the
body’s supply of fats and proteins for energy.
The human body has two adrenal glands on top of
Each almond-size adrenal gland is actually two
glands in one: an inner core, called the adrenal
medulla, and an outer shell, called the adrenal
Adrenal gland hormones
It produces epinephrine (adrenalin) and
norepinephrine (noradrenalin) as a response to stress
situations (fear, danger, cold…)
They increase heart rate, blood pressure, blood glucose
level, blood flow into heart and lungs (Fight or Flight
Produces cortisol, aldosterone, small amounts of
Cortisol makes more energy available to the body.
Aldosterone helps reabsorb sodium (Na+) ions from the
fluids removed by the kidneys so that these ions are not
lost in the urine.
The pineal gland is a
pea-sized gland located
in the brain, which
secretes the hormone
Melatonin seems to be
released by the human
pineal gland as a
response to darkness.
Therefore, the pineal
gland is involved in
The thymus is a
It is involved in the
immune system during
prenatal and postnatal
periods by stimulating
production by its
The main function of the male and female
gonads is in the development of the
reproductive system and secondary sexual
characteristics (even behavior).
They are both endocrine and exocrine glands
Male gonads TESTES, female gonads OVARIES
The ovaries secrete estrogens and
progesterone, and the testes produce
Exocrine function is in the production of
gametes (sperm and egg)