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.