Intro to Hormones

[peachfuzz]

Hormone: A chemical substance produced in the body that controls and regulates the activity of certain cells or organs.

There are two classes of hormones which can be subdivided into further categories:

-Steroid Hormones:
Steroid hormones are derived from cholesterol and are lipid-soluble molecules. Steroid Hormones cause changes within a cell by first passing through the cell membrane of the target cell. Cell membranes are composed of a phospholipid bi-layer which prevents fat-insoluble molecules from diffusing into the cell. Therefore only fat soluble steroid hormones can do this. Once inside the cell the steroid hormone binds with a specific receptor found only in the cytoplasm of the target cell. The receptor bound steroid hormone then travels into the nucleus and binds to another specific receptor on the chromatin. Once bound to the chromatin, this steroid hormone-receptor complex calls for the production of messenger RNA (mRNA) molecules through a process called transcription. The mRNA molecules are then modified and transported to the cytoplasm. The mRNA molecules code for the production of proteins through a process called translation.

-Proteins, Peptides and Modified Amino Acids:
Peptide hormones are a class of peptides that are secreted into the blood stream and have endocrine functions in living animals. The mechanisms underlying the synthesis of protein and peptide hormones are just the same as the synthesis of any other protein, involving transcription of the gene and translation of a messenger RNA (mRNA). Proteins and peptides cannot enter the cell and so act via cell membrane receptors, producing their effects by second messengers, which are activated in the cell as soon as the hormone binds to the receptor. Thus peptide hormones can produce quite rapid responses.

Cells communicate with each other by chemical signals. Three kinds of chemical signaling can be distinguished:

Autocrine- the cell signals itself through a chemical that it synthesizes and then responds to.

Paracrine- Of or relating to a hormone or to a secretion released by endocrine cells into the adjacent cells or surrounding tissue rather than into the bloodstream.

Endocrine - the chemicals are secreted into the blood and carried by blood and tissue fluids to the cells they act upon.

Like all molecules, hormones are synthesized, exist in a biologically active state for a time, and then degrade or are destroyed. Having an appreciation for the half-life and mode of elimination of a hormone aids in understanding its role in physiology and is critical when using hormones as drugs.

A simplified explanation of hormone signaling involves the following:

Biosynthesis - Formation of a chemical compound by a living organism. Protein and peptide hormone synthesis involves transcription of the gene and translation of a messenger RNA (mRNA). Steroid hormones are all synthesized from cholesterol, with a variety of enzymes mediating the transformations into the different products.

Storage – Peptide Hormones are stored in secretory granules. Steroid hormones readily cross cell membranes and therefore cannot be stored; instead they are synthesized as needed.

Secretion – Peptide Hormones are secreted through exocytosis. The membrane of the storage granule fuses with the plasma membrane, which in turn parts, allowing the contents of the granule to be discharged.

Recognition - Each hormone has its own receptor to which it binds, matching like a lock and key.

Signal Transduction – What we are referring to when speaking about our bodies negative feedback loop. When one hormone stimulates the production of a second, the second suppresses the production of the first.

Degradation and Elimination - Steroids are mainly oxidized by cytochrome P450 oxidase enzymes. This reaction introduces oxygen into the steroid ring and allows the structure to be broken up by other enzymes, to form bile acids as final products. These bile acids can then be eliminated through secretion from the liver in the bile. Peptide hormones, by contrast, disappear within an hour or so, because they are both broken down in plasma and tissues and also lost in the urine.

The effects of these powerful hormones include: (taken from wikipedia)
- Stimulation or inhibition of growth
- Induction or suppression of apoptosis (programmed cell death)
- Activation or inhibition of the immune system
- regulating metabolism
- Preparation for a new activity
- Preparation for a new phase of life
- controlling the reproductive cycle

List of Hormones and their roles:

Anterior Lobe Of The Pituitary
Thyroid-stimulating hormone (TSH)
TSH is produced by the pituitary gland and tells the thyroid gland to make and release the hormones thyroxine (T4) and
triiodothyronine (T3).
Follicle-stimulating hormone (FSH)
In women, FSH stimulates production of eggs and a hormone called estradiol during the first half of the menstrual cycle.
In men, FSH stimulates production of sperm.
Luteinizing hormone (LH)
In both sexes, LH stimulates secretion of sex steroids from the gonads. In the testes, LH binds to receptors on Leydig
cells, stimulating synthesis and secretion of testosterone . Theca cells in the ovary respond to LH stimulation by
secretion of testosterone, which is converted into estrogen by adjacent granulosa cells.
Prolactin (PRL)
The conventional view of prolactin is that its major target organ is the mammary gland, and stimulating mammary gland
development and milk production pretty well define its functions.
Growth hormone (GH) A polypeptide hormone secreted by the anterior lobe of the pituitary gland that promotes growth of the body, especially
by stimulating release of somatomedin, and that influences the metabolism of proteins, carbohydrates, and lipids.
Adrenocorticotropic hormone (ACTH)
Adrenocorticotropic hormone, as its name implies, stimulates the adrenal cortex. More specifically, it stimulates
secretion of glucocorticoids such as cortisol, and has little control over secretion of aldosterone.

Posterior Lobe Of Pituitary
Antidiuretic hormone(ADH)
Regulates water in the body. ADH acts on the kidneys to increase total body water. This increases blood volume and blood pressure.
Oxytocin
Stimulates the contraction of smooth muscle of the uterus during labor and facilitates ejection of milk from the breast during nursing.

Hypothalamus
Thyrotropin-releasing hormone (TRH)
Stimulates the release of thyroid-stimulating hormone and prolactin by the anterior pituitary.
Gonadotropin-releasing hormone (GnRH)
The release of GnRH from the hypothalamus regulates the production of gonadotropins in the pituitary and these gonadotropins are responsible for gonadal development and growth in vertebrates.
Growth hormone-releasing hormone (GHRH)
Responsible for normal body growth and development by stimulating protein production in muscle cells and energy release from the breakdown of fats.
Corticotropin-releasing hormone(CRH)
As its name indicates, its acts on cells in the anterior lobe of the pituitary to release adrenocorticotropic hormone (ACTH)
Somatostatin
Somatostatin acts on the anterior lobe of the pituitary to inhibit the release of growth hormone (GH) and inhibit the release of thyroid-stimulating hormone (TSH). Somatostatin is also secreted by cells in the pancreas and in the intestine where it inhibits the secretion of a variety of other hormones.
Dopamine
As a chemical messenger, dopamine is similar to adrenaline. Dopamine affects brain processes that control movement, emotional response, and ability to experience pleasure and pain.

Pineal Gland
Melatonin
Melatonin is a hormone secreted by the pineal gland in the brain that helps regulate other hormones and maintains the body's circadian rhythm. The circadian rhythm is an internal 24-hour time-keeping system that plays a critical role in determining when we fall asleep and when we wake up. Darkness stimulates the production of melatonin while light suppresses its activity.

Thyroid Gland
Thyroxine (T4)
A hormone made by the thyroid gland that has four iodine molecules attached to its molecular structure. T4 and other thyroid hormones help regulate growth and control the rate of chemical reactions (metabolism) in the body.
Calcitonin
Calcitonin is a hormone known to participate in calcium and phosphorus metabolism.

Parathyroid Glands
Parathyroid hormone (PTH)
PTH is the most important regulator of the body's calcium and phosphorus levels. Release of PTH is controlled by the level of calcium in the blood. Low blood calcium levels cause increased PTH to be released, while high blood calcium levels inhibit PTH release.

Adrenal cortex
Glucocorticoids (e.g. cortisol)
Glucocorticoids are naturally-produced steroid hormones, or synthetic compounds, that inhibit the process of inflammation.
Mineralocorticoids (e.g. aldosterone)
Mineralcorticoids are responsible for the reabsorption of sodium and chloride. Decreased mineralcorticoid secretion results in loss of sodium, which causes an increase of potassium in the blood. High blood levels of potassium can lead to life threatening heart problems.
Androgens (e.g. testosterone)
Any substance that promotes the development of male secondary sexual characteristics.

Adrenal Medulla
Adrenaline
released into the bloodstream in response to physical or mental stress, as from fear or injury. It initiates many bodily responses, including the stimulation of heart action and an increase in blood pressure, metabolic rate, and blood glucose concentration. Also called adrenaline.
Noradrenaline
A substance that acts both as a neurotransmitter and hormone, secreted in the central nervous system, at the nerve endings of the sympathetic nervous system, and by the adrenal gland. Norepinephrine is similar to epinephrine in its physiological effects but acts to regulate regular physiologic activity rather than being released in response to stress.

Ovarian Follicle
Estrogens (e.g., estradiol)
Any of various natural steroids (as estradiol) that are formed from androgen precursors, that are secreted chiefly by the ovaries, placenta, adipose tissue,and testes, and that stimulate the development of female secondary sex characteristics and promote the growth and maintenance of the female reproductive system

Corpus luteum and placenta
Progesterone
A steroid hormone that prepares the uterus for pregnancy, maintains pregnancy, and promotes development of the mammary glands. The main sources of progesterone are the ovary and the placenta.

Trophoblast and Placenta
Human chorionic gonadotropin (HCG)
Its role is to prevent the disintegration of the corpus luteum of the ovary and thereby maintain progesterone production that is critical for a pregnancy in humans. hCG may have additional functions; for instance, it is thought that hCG affects the immune tolerance of the pregnancy. In males, hCG mimics LH and helps restore and maintain testosterone production in the testes. As such, hCG is commonly used during and after steroid cycles to maintain and restore testicular size as well as endogenous testosterone production. However, if hCG is used for too long and in too high a dose, the resulting rise in natural testosterone will eventually inhibit its own production via negative feedback on the hypothalamus and pituitary.

Testes
Androgens (e.g. testosterone)
Any substance that promotes the development of male secondary sexual characteristics.

Pancreas
Insulin
A polypeptide hormone secreted by the islets of Langerhans and functioning in the regulation of the metabolism of carbohydrates and fats, especially the conversion of glucose to glycogen, which lowers the blood glucose level.
Glucagon
The protein hormone secreted by the pancreas which is known to influence a wide variety of metabolic reactions. Glucagon, along with insulin and other hormones, plays a role in the complex and dynamic process of maintaining adequate supplies of sugar in the blood. Glucagon has often been called the hyperglycemic-glycogenolytic factor because it causes the breakdown of liver glycogen to sugar (a process known as glycogenolysis) and thereby increases the concentration of sugar in the bloodstream
Somatostatin
Somatostatin acts on the anterior lobe of the pituitary to inhibit the release of growth hormone (GH) and inhibit the release of thyroid-stimulating hormone (TSH). Somatostatin is also secreted by cells in the pancreas and in the intestine where it inhibits the secretion of a variety of other hormones.
Amylin
Although amylin's complete function may not yet be known, it has been shown to slow gastric emptying, promote satiety, inhibit secretion of glucagon during hyperglycemia, and therein reduce the total insulin demand

Kidney
Erythropoietin (EPO)
Calcitriol

Skin
Calciferol (vitamin D3)

Heart
Atrial-Natriuretic Peptide (ANP)

Stomach and Intestine
Gastrin
Secretin
Cholecystokinin (CCK)
Incretins peptides
Somatostatin
Neuropeptide Y
Ghrelin
PYY3-36

Liver
Insulin-like growth factor-1 (IGF-1)
Angiotensinogen
Thrombopoietin

Adipocytes
Leptin
Retinol Binding Protein 4
Adiponectin

[stallion_1]

[one8nine]

are you going to expand on these?

[peachfuzz]

There was a thousand different directions I could have taken this but I tried to keep it as simple as possible. Open to suggestions or changes. I realize i still need to list the roles of each hormone and ill get to that when i have more time.

[stallion_1]

nice job on the copy/paste

[peachfuzz]

nice job on the copy/paste

yes much of this is from other sources which I can reference if it pleases you. However i didnt feel the need to sit and map out every hormone when its already done for me.

[stallion_1]

good job buddy

[peachfuzz]

tis been updated a wee bit.

[peachfuzz]

to the top!

[peachfuzz]

bizump

[Garbanzo Dude]

Good stuff.....fuzz man!

[peachfuzz]

thank you kind sir

[peachfuzz]

bump

[peachfuzz]

never finished this but ill bump it anyway....