Endocrine System
The endocrine system is made up of glands that produce and secrete
hormones,
chemical substances produced in the body that regulate the activity of
cells or
organs. These hormones regulate the body's growth, metabolism (the
physical and chemical processes of the body), and sexual development and
function. The hormones are released into the bloodstream and may affect
one or several organs throughout the body.
Hormones are chemical messengers created by the body. They transfer
information from one set of cells to another to coordinate the functions
of different parts of the body.
The major glands of the endocrine system are the hypothalamus,
pituitary, thyroid, parathyroids, adrenals, pineal body, and the
reproductive organs (ovaries and testes). The pancreas is also a part of
this system; it has a role in hormone production as well as in
digestion.
The endocrine system is regulated by feedback in much the same way
that a thermostat regulates the temperature in a room. For the hormones
that are regulated by the pituitary gland, a signal is sent from the
hypothalamus to the pituitary gland in the form of a
"releasing hormone," which stimulates the pituitary to secrete a
"stimulating hormone" into the circulation. The stimulating hormone then
signals the target gland to secrete its hormone. As the level of this
hormone rises in the circulation, the hypothalamus and the pituitary
gland shut down secretion of the releasing hormone and the stimulating
hormone, which in turn slows the secretion by the target gland. This
system results in stable blood concentrations of the hormones that are
regulated by the pituitary gland.
Pituitary Gland
The pituitary gland is located at the base of the brain beneath the
hypothalamus and is no larger than a pea. It is often considered the
most important part of the endocrine system because it produces hormones
that control many functions of other endocrine glands. When the
pituitary gland does not produce one or more of its hormones or not
enough of them, it is called hypopituitarism.
The pituitary gland is divided into two parts: the anterior lobe and
the posterior lobe. The anterior lobe produces the following hormones,
which are regulated by the hypothalamus:
- Growth hormone: Stimulates growth of bone and tissue (growth hormone deficiency in children results in growth failure. Growth hormone deficiency in adults results in problems in maintaining proper amounts of body fat and muscle and bone mass. It is also involved in emotional well-being.)
- Thyroid-stimulating hormone (TSH): Stimulates the thyroid gland to produce thyroid hormones (A lack of thyroid hormones either because of a defect in the pituitary or the thyroid itself is called hypothyroidism.)
- Adrenocorticotropin hormone (ACTH): Stimulates the adrenal gland to produce several related steroid hormones
- Luteinizing hormone (LH) and follicle-stimulating hormone (FSH): Hormones that control sexual function and production of the sex steroids, estrogen and progesterone in females or testosterone in males
- Prolactin: Hormone that stimulates milk production in females
The posterior lobe produces the following hormones, which are not regulated by the hypothalamus:
- Antidiuretic hormone (vasopressin): Controls water loss by the kidneys
- Oxytocin: Contracts the uterus during childbirth and stimulates milk production
The hormones secreted by the posterior pituitary are actually
produced in the brain and carried to the pituitary gland through nerves.
They are stored in the pituitary gland.
What Is Acromegaly?
Acromegaly is a growth disorder caused by excessive production of
growth hormone (GH) by the pituitary gland. The pituitary gland is a
hormone-producing organ at the base of the brain, behind the eyes, and
at the middle of the brain between the ears. Children cannot grow to
normal height if they do not have enough GH, but too much causes
prepubertal children to develop giantism, a condition in which the
entire body or any of its parts grow too large. In adults, too much GH
causes acromegaly, a disorder in which parts of the body, especially the
head, face, hands, and feet, gradually get bigger. GH affects growth by
stimulating the formation of other hormones. These hormones are mostly
made by the liver in response to GH stimulation and are called
somatomedins (somatotropin-mediating hormones or insulinlike growth
factors).
Thyroid Gland
The thyroid gland is located in the lower front part of the neck. It
produces thyroid hormones that regulate the body's metabolism. It also
plays a role in bone growth and development of the brain and nervous system
in children. The pituitary gland controls the release of thyroid
hormones. Thyroid hormones also help maintain normal blood pressure,
heart rate, digestion, muscle tone, and reproductive functions.
Thyroid Problems Symptoms
Symptoms of thyroid problems depends on the age of the person and the exact
problem with the thyroid. For example, some symptoms of hypothyroidism in
children include:
- Symptoms similar to adult symptoms
- Excessive fatigue
- Poor growth
- Poor school performance
Symptoms of hypothyroidism in adults include:
- Easy fatigue, exhaustion
- Poor tolerance to cold temperatures
- Constipation
- Carpal tunnel syndrome (pain at the wrists and numbness of the hands)
Some of the symptoms of hyperthyroidism in adults include:
- Insomnia
- Hand tremors
- Nervousness
Cushing's syndrome
Cushing's syndrome describes the signs and symptoms associated with prolonged exposure to inappropriately high levels of the hormone cortisol. This can be caused by taking glucocorticoid drugs, or diseases that result in excess cortisol, adrenocorticotropic hormone (ACTH), or CRH levels.
Cushing's disease refers to a pituitary-dependent cause of Cushing's syndrome: a tumor (adenoma) in the pituitary gland produces large amounts of ACTH, causing the adrenal glands to produce elevated levels of cortisol. It is the most common non-iatrogenic cause of Cushing's syndrome, responsible for 70% of cases excluding glucocorticoid related cases
This pathology was described by Harvey Cushing in 1932. The syndrome is also called Itsenko-Cushing syndrome, hyperadrenocorticism or hypercorticism.
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