Endocrine Hormones and Disorders

Hyposecretion of Anti-Diuretic Hormone - Diabetes insipidus

Due to decreased production of anti-diuretic hormone in the supraoptic nucleus of the hypothalamus. Often associated with a head injury.

Symptoms:  Excessive diuresis and thirst (polyuria and polydipsia).

Hyposecretion of Growth hormone - Pituitary dwarfism

Due to decreased production of growth hormone from the somatotropic cells of the anterior pituitary.  Generally due to a nonmalignant adenoma of the non-somatotropic tissue of the anterior pituitary.

Symptoms:

1.  hypoglycemia

2.  In Lorain dwarfism:
     a.  arrested sexual
     b.  stunted growth
     c.  normal intelligence
3.  In Frolich's dwarfism:
     a.  arrested sexual
     b.  stunted growth
     c.  mental retardation









Hypersecretion of growth hormone - Giantism and Acromegaly
Pituitary giantism is due to overproduction of growth hormone during childhood.  Usually caused by an adenoma of the somatotropic cells.
Symptoms:  Excessive growth, hyperglycemia, diabetes mellitus, osteoporosis and high basal metabolic rate (BMR).
Acromegaly excessive appositional growth of the skeleton resulting in thickening of the digits and facial features ("lantern jaw" and protruding brow ridges). Increase in height does not occur since at the time of the onset of acromegaly the epiphyseal plates have calcified.  Except for growth in height, symptoms are the same as those for giantism.

Hyposecretion of thymus or absence of gland
DiGeorge syndrome occurs in children born without a thymus gland.  As a result, there is a lack of thymosin production.  Thymosin is needed to stimulate the differentiation of T lymphocytes.
Symptoms:
1.  Little or no immune response.
2.  Inability to resist bacterial, viral or fungal infections.
3.  A lack of cancer cell surveillance.
4.  Inability to reject foreign tissues.






Hyposecretion of thyroid hormone
Myxedema occurs in the adult due to low thyroxine production.  This can be produced by an adenoma of non-thyrotropic cells in the anterior pituitary, low iodine in the diet or autoimmune destruction of the thyroid (Hashimoto's thyroiditis).

Symptoms:
1.  Low BMR and lower body temperature.
2.  Increased fat deposition and lethargy
3.  Low blood pressure, heart rate and respiratory rate
4.  Goiter due to low levels of iodine in blood.
    Cretinism is due to hypothyroidism in infants or children.  In addition to the symptoms seen in myxedema, the patient exhibits stunted growth, mental deficiency and immature sexual development.

Hypersecretion of thyroid hormone
Overproduction of thyroid hormone can be due to adenoma of the thyrotropic cells of the anterior pituitary, a thyroid tumor or an autoimmune reaction to TSH receptors on thyrotropic cells (Graves' disease).
Symptoms:
1.  High BMR & body temperature with profuse sweating.
2.  Increased appetite with weight loss.
3.  Increased heart rate, blood pressure and respiratory rate.
4.  Muscular tremor and nervousness
5.  Cardiac arrhythmias.
6.  Toxic goiter and exophthalmia (Graves' disease).

Hypersecretion of parathyroid hormone
An excess of parathyroid hormone production is due to a tumor of the parathyroid gland.

Symptoms:
1.  High blood calcium.
2.  Decalcification of bone which leads to fractures
3.  Cardiac arrhythmias.
4.  Tetany in skeletal muscles.



Hyposecretion of parathyroid hormone
The non-function of the parathyroid glands produces below normal levels of calcium in the blood.
Symptoms:
1.  Spontaneous nerve depolarization cause convulsions.
2.  Cuffing the arm leads to irreversible flexion of fingers.

Hyposecretion of insulin - Diabetes mellitus
Due to a lack of insulin from nonfunctioning beta cells of the pancreatic islets.  There are two primary forms of this disease:
1.  Type I or juvenile onset diabetes mellitus generally occurs in people younger than 20 years (insulin dependent diabetes).  This is the consequence of an autoimmune destruction of islet beta cells.
2.  Type II or late onset diabetes mellitus usually occurs in people who are over the age of 40 and overweight.  In many cases, diet and exercise can reverse symptoms.

Symptoms: 
1.  Hyperglycemia
2.  Polyuria, polydipsia and polyphagia.
3.  Ketoacidosis which can lead to diabetic coma and death.

Hypersecretion of insulin - hyperinsulinism
A tumor of the islet beta cells will cause an overproduction of insulin.  This will produce a pronounced hypoglycemia.  There is a very low incidence of this condition.
Symptoms:
1.  Anxiety and sweating.
2.  Body tremors
3.  Elevated body temperature
4.  Disorientation
4.  The patient can go into Insulin shock due to brain hypoglycemia. 









Hyposecretion of glucagon - chronic hypoglycemia

A decreased ability to secrete glucagon from pancreatic alpha cells has been associated with chronic hypoglycemia.  

Other contributing factors to this condition would be:
1.  A beta cell tumor
2.  Defect in the mechanism releasing glucose from the liver.
3.  Addison's disease - low levels of corticosteroids which enhance glucose production.
4.  Hyposecretion of growth hormone 

Hyposecretion of adrenal steroids - Addison's disease
This is an uncommon disease since both adrenal glands must suffer a 90% loss of function before symptoms appear.  In 25% of the cases, degeneration of the adrenal cortex is due to chronic TB.  Autoimmune destruction of the cortical tissue is believed to be another cause.

Symptoms:
1.  Hypoglycemia, hyponatremia and hyperkalemia
2.  Severe dehydration leads to hypovolemia.
3.  Gastrointestinal disorders
4.  Low tolerance to stress or trauma
5.  Hyperpigmentation due to elevated levels of ACTH in blood.

Hypersecretion of adrenal steroids - Cushing's syndrome
Chief causes of Cushing's syndrome:
1.  Hypersecretion of ACTH - Pituitary Cushing's syndrome is responsible for 60 to 70% of these cases.  This condition is brought on by a pituitary adenoma.2.  Hypersecretion of adrenal steroids due to an adenoma of the adrenal cortex (20% of the cases) produces low levels of ACTH by negative feedback.  This is called adrenal Cushing's syndrome.
3.  Hypersecretion of ACTH by a non-endocrine cancer, e.g., lung carcinoma.  This is called paraneoplastic Cushing's syndrome and is responsible for 10 to 15% of the cases.
4.  Iatrogenic Cushing's syndrome is due to the long term use of glucocorticoids to control inflammation and edema or autoimmune diseases like rheumatoid arthritis.

Symptoms:
1.  Hyperglycemia due to enhanced gluconeogenesis.
2.  Easy bruising and muscular weakness.
3.  Decreased immunity.
4.  Hypernatremia leading to excessive water retention.
5.  Hyperkalcemia and high blood pressure.
6.  Shifting "moon face" and "Buffalo hump".
7.  In a male child - Muscular hypertrophy
8.  In a female child or adult - Virilsm (bearded lady).

Source: 
http://faculty.ucc.edu/biology-potter/Endocrine%20hormones%20and%20disorders.htm

Mechanism of Hormone Action

The endocrine system acts by releasing hormones that in turn trigger actions in specific target cells. Receptors on target cell membranes bind only to one type of hormone. More than fifty human hormones have been identified; all act by binding to receptor molecules. The binding hormone changes the shape of the receptor causing the response to the hormone. There are two mechanisms of hormone action on all target cells.

Nonsteroid Hormones

Nonsteroid hormones (water soluble) do not enter the cell but bind to plasma membrane receptors, generating a chemical signal (second messenger) inside the target cell. Five different second messenger chemicals, including cyclic AMP have been identified. Second messengers activate other intracellular chemicals to produce the target cell response.

The action of nonsteroid hormones. Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com).

Steroid Hormones

The second mechanism involves steroid hormones, which pass through the plasma membrane and act in a two step process. Steroid hormones bind, once inside the cell, to the nuclear membrane receptors, producing an activated hormone-receptor complex. The activated hormone-receptor complex binds to DNA and activates specific genes, increasing production of proteins.

The action of steroid hormones. Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com).

Classes of Hormones

Hormones are classified into 2 categories depending on their chemical make-up and solubility: water soluble and lipid soluble hormones. Each of these classes of hormones has specific mechanisms for their function that dictate how they affect their target cells.

Water-Soluble Hormones

The water soluble hormone include the peptide and amino-acid hormones such as insulin, epinephrine, HGH, and oxytocin. As their name indicates, these hormones are soluble in water, they unable to pass through the phospholipid bilayer of the plasma membrane and are therefore dependent upon receptor molecules on the surface cell. When a water-soluble hormone binds to a receptor molecule on the surface of the cell, it triggers a reaction inside of the cell. This reaction may change a factor inside of the cell such as the permeability of the membrane or the activation of another molecule. A common reaction is to cause molecules of cyclic adenosine monophosphate (cAMP) to be synthesized from adenosine triphosphate (ATP) present int the cell. cAMP acts as a second messenger within the cell where it binds to a second receptor to change the function of the cell's physiology.

Lipid-Soluble Hormones

Lipid soluble hormones include the steroid hormones such as testosterone, estrogens, glococorticoids, and mineralocorticoids. Because they are soluble in lipids, these hormones are able to pass directly through the phospolipids bilayer of the plasma membrane and bind directly to receptors inside the cell nucleus. Lipid soluble hormones are able to directly control the function of a cell from these receptors, often triggering the transcription of particular genes in the DNA to produce messenger RNA (mRNA) that are used to make proteins that affect the cell's growth and function.

Source: http://www.innerbody.com/image/endoov.html

Part of Endocrine System

Hypothalamus

The hypothalamus is a part of the brain located superior and anterior to the brain stem and inferior to the thalamus. It serves many different functions in the nerveous system, and is also responsible for the direct control of the endocrine system through the pituitary gland. The hypothalamus contains special cells called neurosecretory cells (neurons that secretes hormones-red), that's some hormones that released by these cells:

1. Thyrotropin-releasing hormone (TRH)

2. Growth hormone-releasing hormong (GHRH)

3. Growth hormone-inhibiting hormone (GHIH)

4. Gonadotropin-releasing hormone (GnRH)

5. Corticotropin-releasing hormone (CRH)

6. Oxytocin

7. Antideuretic hormone (ADH)

Pituitary Gland

The pituitary galnd also known as the hypophisis, is a small pea-sized lump of tissue connected to he inferior portion of the hypothalamus of the brain. Many blood vessels surround the pituitary gland to carry the hormones it releases through out the body. Situated in a small depression in the sphenoid bone called tha sella turcica, the pituitary glands is actually made of 2 completely separate structure: the posterior and anterior pituitary gland.

Posterior Pituitary
This gland is actually not glandular tissue at all, but nerveous tissue instead. In posterior gland also has neurosecretory cell, these cells create 2 hormones in the hypothalamus that are stored and released by the posterior pituitary: 
1. Oxytocin: triggers uterine contraction during childbirth and release of milk 
2. Antidiuretic hormone (ADH): prevents water loss in body by increasing re-take up water

Anterior Pituitary
The anterior glands is the true glandular part of the pituitary gland, the function of the anterior pituitary gland is controlled by releasing and inhibiting hormones of the hypothalamus. The anterior produces 6 important hormones:
1. Thyroid Stimulating Hormones (TSH), responsible for stimulation of the thyroid glands
2. Adrenocorticotropic Hormones (ACTH), stimulated adrenal cortex to produce its hormone
3. Follicle Stimulating Hormones(FSH), stimulate follicle cell to produce gametes
4. Luteinizing Hormones (LH), stimulate gonads to produce sex hormones
5. Human Growth Hormones (HGH), affect many target cell to stimulate their growth
6. Prolactin (PRL), stimulated the mmary glands of the breast to produce milk.


Thyroid and Parathyroid Gland

The thyroid gland is a butterfly-shaped gland located at the base of the neck and wrapped around the lateral sides of trachea. The thyroid gland produces 3 major hormones: calcitonin, triodothyronine (T3), and Thyroxine (T4). The parathyroid glands are 4 small masses of glandular tissue found on the posterior side of the thyroid gland. The parathyroid gland produces the hormone parathyroid hormone (PTH), which is involved in calcium ion homeostasis. PTH is stimulates the osteoclast to breakdown the calcium containing bone matrix to release free calcium ion into the blood stream.


Adrenal Glands
The adrenal glands are a pair of roughly triangular glands found immediately superior to the kidney. The adrenal glands are each made of 2 distinct layers, each with their own unique function:

Adrenal Cortex

Produces many cortical hormones in 3 classes:
1. Glucocortocoids have a diverse function, breakdown protein and lipids to produce glucose.
2. Mineralocorticoids, help to regulate the concentration of mineral ions in the body
3. Androgens, to regulate the growth and activity of cells that receptive to male hormones

Adrenal Medula
Produces the hormones epinephrine and norepinephrine under stimulation by the sympathetic division of the autonomic nerveous system. Both of hormones helps to increase the flow of the blood to the brain and muscles to improve the "fight-or-flight" response to stress. These hormones also work to increase heart rate, breathing rate, and also blood pressure.


Pancreas Gland
The pancreas is alrge gland located in the abdominal cavity just inferior and posteror to the stomach. The pancreas is considered to be a heterocrine gland as it contains both endocrine and exocrine tissues. The endocrine cell of the pancreas make up just 1% of the total mass of the pancreas and found in small groups throughout the pancreas called islets of langerrhans. Within these islet are 2 types of cell, alpha and beta cells. The alpha cells produce the hormone glucagon, which responsible for raising blood glucose level. The beta cells produce the insuline hormone, which is responsible for lowering blood glucose levels after a meal. 



Thymus

The thymus is a soft, triangular-shaped organ found in the chest posterior to the sternum. The thymus produced hormones called thymosins that help to train and develop T-lympocytes during fetal development and childhood. T-lympocytes to protect the body pathogens throughout a person's entire life.


Gonads
The gonads are the main source of sex hormones. In males, they are located in the scrotum. Male gonad or testes, secrete hormones called androgens, the most important of which testosterone. These hormones regulate body changes associated with sexual deveopmnet, including enlargement the penis, the growth spurt that occur during puberty, and the appearance of the other male secondary sex characteristic.
The female gonads, the ovaries are located in the pelvis. They produce eggs and secrete the female hormone estrogen and progesterone. Estrogen is involved in the development of female sexual features such as breast growth, the accumulation of body fat around hips and thighs, and the growth spurt that ossurs during puberty. Both of these hormones also involved in pregnancy and the regulation of the menstrual cycle.

Source: innerbody.com

About Endocrine System

Although we rarely think about them, the glands of the endocrine system and the hormones they release influence almost every cell, organ, and function of our bodies. The endocrine system is instrumental in regulating mood, growth and development, tissue function, and metabolism, as well as sexual function and reproductive processes.

In general, the endocrine system is in charge of body processes that happen slowly, such as cell growth. Faster processes like breathing and body movement are controlled by the nervous system. But even though the nervous system and endocrine system are separate systems, they often work together to help the body function properly.

The foundation of the endocrine system are the hormones and gland. As the body's chemical messagers, hormones transfer information and instruction from one set of cells to another. Although many different hormones circulate through out he bloodstream, each one affects only the cells that are genetically programmed to receive and respond to its message. Hormones  levels can be influenced by factor such as stress, infection, and changes in the balance of fluid and minerals in blood.

A gland is a group of cells that produces and secretes, or gives off, chemicals. A gland selects and removes materials from blood, processes them, and secretes the finished chemical product for use somewhere in the body.

Some types of glands release their secretions in specifics areas. For instance, exocrine glands, such as the sweat and salivary glands, release secretion in the skin or inside of the mouth. Endocrine gland, on the other hand, release more than 20 major hormones directly into the bloodstream where they can be transported to cells in other parts of the body.

Source: kidshealth.org