Endocrine SystemEndocrine System

Endocrine SystemEndocrine System

This system helps to regulate all the This system helps to regulate all the body's functions. body's functions.

It is made up of ductless (without tubes) It is made up of ductless (without tubes) glands which produce and release glands which produce and release hormones directly into the bloodstream.hormones directly into the bloodstream.

Endocrine GlandsEndocrine Glands

These are the major hormone-producing These are the major hormone-producing organs of the endocrine system. They organs of the endocrine system. They release hormones directly into the release hormones directly into the bloodstream.bloodstream.

HormoneHormone

A chemical substance secreted by an A chemical substance secreted by an endocrine gland or group of endocrine endocrine gland or group of endocrine cells that acts to control or regulate cells that acts to control or regulate specific physiological processes, including specific physiological processes, including growth, metabolism, and reproduction.growth, metabolism, and reproduction.

THE ENDOCRINE THE ENDOCRINE GLANDSGLANDS

Pituitary GlandPituitary Gland

The pituitary gland is called the master gland.The pituitary gland is called the master gland. The hormones of the pituitary gland are called The hormones of the pituitary gland are called

““tropic hormonestropic hormones”” . . It is located within the brain. It hangs from the It is located within the brain. It hangs from the

hypothalamus. It is just about the size of a pea.hypothalamus. It is just about the size of a pea. The pituitary is broken down into two parts, theThe pituitary is broken down into two parts, the

anterior lobeanterior lobe and theand the posterior lobeposterior lobe..

Hormones controlled by the Hormones controlled by the anterior lobeanterior lobe of of

the pituitary include:the pituitary include:

Human Growth Hormone Human Growth Hormone (Somatotropin)(Somatotropin) stimulates cell division and the growth of stimulates cell division and the growth of

the muscles and bones. the muscles and bones. Thyroid Stimulating HormoneThyroid Stimulating Hormone

stimulates the thyroid gland to produce stimulates the thyroid gland to produce hormones. hormones.

Adrenocorticotropic HormoneAdrenocorticotropic Hormone stimulates the adrenal cortex of the adrenal stimulates the adrenal cortex of the adrenal

glands. glands. ProlactinProlactin

stimulates the production of breast milk in stimulates the production of breast milk in females. females.

Follicle Stimulating HormonesFollicle Stimulating Hormones stimulates the development of eggs in the stimulates the development of eggs in the

ovaries and sperm in the testes. ovaries and sperm in the testes. Luteinizing HormoneLuteinizing Hormone

causes sex hormone secretion in both males causes sex hormone secretion in both males and females and also causes ovulation in and females and also causes ovulation in females. females.

Hormones controlled by the Hormones controlled by the posterior lobeposterior lobe of of

the pituitary include:the pituitary include:

Antidiuretic Hormone/Vasopressin Antidiuretic Hormone/Vasopressin helps the body to conserve water by helps the body to conserve water by

promoting the reabsorption of water from promoting the reabsorption of water from the kidneys. the kidneys.

Oxytocin Oxytocin causes contraction of the uterine muscles causes contraction of the uterine muscles

and promotes the release of milk from the and promotes the release of milk from the breast.breast.

Pineal GlandPineal Gland

It is an outgrowth of the brain. It produces It is an outgrowth of the brain. It produces melatoninmelatonin..

The The melatoninmelatonin forms part of the system forms part of the system that regulates the that regulates the circadian cycle (body’s (body’s day-night cycles). day-night cycles).

Normally, the production of melatonin by Normally, the production of melatonin by the pineal gland is inhibited by the pineal gland is inhibited by light and and permitted by permitted by darkness. For this reason . For this reason melatonin has been called melatonin has been called ""the hormone the hormone of darknessof darkness"". .

The secretion of melatonin peaks in the The secretion of melatonin peaks in the middle of the night, and gradually falls middle of the night, and gradually falls during the second half of the night. during the second half of the night.

If the melatonin is low, the body becomes If the melatonin is low, the body becomes active.active.

At the end of the day, when there is high At the end of the day, when there is high melatonin in the body, the overall level of melatonin in the body, the overall level of activity reduces in preparation for sleep.activity reduces in preparation for sleep.

Thyroid GlandThyroid Gland

It is located at the base of the neck.It is located at the base of the neck.It produces It produces thyroxinthyroxin that controls the that controls the

rate at which the body cells use food to rate at which the body cells use food to release energy.release energy.

It also produces It also produces calcitonincalcitonin which which reduces blood calcium levels by causing reduces blood calcium levels by causing calcium to be deposited in the bones.calcium to be deposited in the bones.

Thyroid hormones also help in Thyroid hormones also help in regulating body growth and regulating body growth and development.development.

Differences in metabolic rate determine Differences in metabolic rate determine how alert and energetic people are and how alert and energetic people are and how fat or thin they tend to be.how fat or thin they tend to be.

Parathyroid GlandsParathyroid Glands These are two pairs of pea-sized glands These are two pairs of pea-sized glands

found near the thyroid gland. found near the thyroid gland. The hormone produced by these glands, The hormone produced by these glands,

called called parathormoneparathormone, helps control the , helps control the level of the calcium in the blood. If the level of the calcium in the blood. If the calcium level is low, the glands increase calcium level is low, the glands increase their hormone production which causes the their hormone production which causes the bones to release more calcium into the bones to release more calcium into the blood. If the blood level of calcium is too blood. If the blood level of calcium is too high, the glands lessen their production of high, the glands lessen their production of the hormone. the hormone.

Thymus GlandsThymus Glands

It is located in the upper thorax behind the It is located in the upper thorax behind the breast bone and extends below the thyroid breast bone and extends below the thyroid gland. gland.

It forms part of the body’s immune system. It forms part of the body’s immune system. The function of the gland is to cause The function of the gland is to cause lymphocyteslymphocytes (white blood cells) to (white blood cells) to become become T cellsT cells – cells which become part – cells which become part of the body’s defense against infection.of the body’s defense against infection.

Adrenal GlandsAdrenal Glands

The adrenals are a pair of cone-shaped glands, The adrenals are a pair of cone-shaped glands, each on top of a kidney.each on top of a kidney.

An adrenal gland has two parts – the An adrenal gland has two parts – the cortexcortex or or the outer part, and the the outer part, and the medullamedulla or the inner part.or the inner part.

The The cortexcortex produces produces corticoidscorticoids that affect the that affect the body body metabolismmetabolism (is the process by which the (is the process by which the body converts food into energy).body converts food into energy).

The The medullamedulla produces produces epinephrineepinephrine (adrenaline)(adrenaline) which mimics the sympathetic which mimics the sympathetic nervous system.nervous system.

Pancreatic IsletsPancreatic Islets

Scattered throughout the pancreas are tiny Scattered throughout the pancreas are tiny glandular tissues called pancreatic islets glandular tissues called pancreatic islets (also called (also called islets of Langerhansislets of Langerhans) that ) that produce the hormones produce the hormones glucagonglucagon and and insulininsulin. .

InsulinInsulin lowers blood sugar level while lowers blood sugar level while glucagonglucagon raises blood sugar level. raises blood sugar level.

GonadsGonads

TestesTestes They produce They produce androgensandrogens

(testosterone)(testosterone) which causes the which causes the development of male secondary development of male secondary sex characteristics.sex characteristics.

OvariesOvaries They produce They produce estrogenestrogen and and

progesteroneprogesterone. . EstrogenEstrogen stimulates the development stimulates the development

of the female secondary sex of the female secondary sex characteristics, as well as the growth characteristics, as well as the growth of the inner lining of the uterus in of the inner lining of the uterus in preparation for implantation and preparation for implantation and development of a fertilized egg.development of a fertilized egg.

In support of this reproductive function, In support of this reproductive function, the the progesteroneprogesterone also promotes also promotes growth of the uterine lining. growth of the uterine lining.

Disorders of Endocrine System

A glandular disorder may be:

Functional It results in the overproduction or underproduction

of the hormones that the gland produces.

Anatomical Abnormal changes in the structure or anatomy of a

gland, such as the enlargement of the gland.

Autoimmune Abnormal functioning of the immune system that

causes your immune system to produce antibodies against your own tissues.

Hypothyroidism

It is the underproductivity of the thyroid due to lack of iodine in the diet. A symptom of hypothyroidism is goiter, or the enlargement of the thyroid gland.

If the cause of goiter is lack of iodine, a patient should have more fish and iodized salt in his or her diet. If the goiter is too large, it can be removed by surgery.

Hyperthyroidism

Graves’ disease is a form of hyperthyroidism or the overproductivity of the thyroid gland. This is caused by an autoimmune disorder. The symptoms of this disease include increased appetite, weight gain, and dry skin. In some cases, a toxic goiter develops and the eyes bulge.

A long term treatment is needed for this disease. In some cases, one-dose radioactive iodine is used as treatment or the part of the gland is removed by surgery.

Cretinism

Underproductivity of the thyroid gland results in decreased production of thyroxin. A deficiency in thyroxin during the development of a fetus can cause cretinism. A cretin is short in height and has mental retardation.

Gigantism

Overproduction of the growth hormone causes gigantism or excessive tallness (adult height of 2.4 to 2.7 meters).

Dwarfism

Underproduction of the growth hormone causes dwarfism where the body proportions are normal but adult height does not exceed 1.2 meters. Adults with this height are referred to as midgets. Dwarfs are adults who are short and with body proportions that are not normal.

Diabetes Mellitus

It is a disorder in which the pancreas produces little or no insulin. Without insulin, blood sugar level rises. Diabetes is found to run in families. Children of a diabetic parent may likely develop the disease.

Treatment of diabetes includes maintenance of normal weight, regular exercise, and proper diet. In cases where the patient is dependent on insulin, regular injection of insulin is recommended.

Hypofunction of Testes and Ovaries

Hypofunction of the testes can be the result of some abnormality in development before birth. This causes failure of the development of male secondary sex characteristics.

Hypofuntion of the ovaries may cause a female not to menstruate; it may also cause infertility.