The endocrine system is a system of glands that involve the release of extracellular signaling molecules known as hormones. The endocrine system is instrumental in regulating metabolism, growth, development, puberty, tissue function, internal environment (temperature,water balance,ions) and also plays a part in determining mood.^[1] The field of study that deals with disorders of endocrine glands is endocrinology, a branch of the wider field of internal medicine.

Contents 1 Function 1.1 Types of signaling 1.1.1 Endocrine 1.1.2 Autocrine 1.1.3 Paracrine 1.1.4 Juxtacrine 2 Table of endocrine glands and secreted hormones 2.1 Hypothalamus 2.2 Pineal body (epiphysis) 2.3 Pituitary Gland (hypophysis) 2.3.1 Anterior pituitary lobe (adenohypophysis) 2.3.2 Posterior pituitary lobe (neurohypophysis) 2.3.3 Intermediate pituitary lobe (pars intermedia) 2.4 Thyroid 2.5 Parathyroid 2.6 Heart 2.7 Striated muscle 2.8 Skin 2.9 Adipose tissue 2.10 Stomach 2.11 Duodenum 2.12 Liver 2.13 Pancreas 2.14 Kidney 2.15 Adrenal glands 2.15.1 Adrenal cortex 2.15.2 Adrenal medulla 2.16 Testes 2.17 Ovarian follicle / Corpus luteum 2.18 Placenta (when pregnant) 2.19 Uterus (when pregnant) 3 See also 4 References

[edit] Function

The endocrine system is an information signal system much like the nervous system. However, the nervous system uses nerves to conduct information, where as the endocrine system mainly uses blood vessels as information channels. Glands located in many regions of the body, for example the testis, release into the bloodstream specific chemical messengers called hormones. Hormones regulate many functions of an organism, including mood, growth and development, tissue function, and metabolism.

[edit] Types of signaling

The typical mode of cell signaling in the endocrine system is endocrine signaling. However, there are also other modes, i.e., paracrine, autocrine, and neuroendocrine signaling.^[2] Purely neurocrine signaling between neurons, on the other hand, belongs completely to the nervous system.

[edit] Endocrine

The endocrine system is made up of a series of ductless glands that produce chemical messages called hormones

A number of glands that signal each other in sequence is usually referred to as an axis, for example, the hypothalamic-pituitary-adrenal axis. Typical endocrine glands are the pituitary, thyroid, and adrenal glands. Features of endocrine glands are, in general, their ductless nature, their vascularity, and usually the presence of intracellular vacuoles or granules storing their hormones. In contrast, exocrine glands, such as salivary glands, sweat glands, and glands within the gastrointestinal tract, tend to be much less vascular and have ducts or a hollow lumen. Also controls metabolism in our body system.

[edit] Autocrine

Other signaling can target the same cell, or other cells.^{[citation needed]}

This section requires expansion.

[edit] Paracrine

Paracrine signaling is where the target cell is nearby.^{[citation needed]}

This section requires expansion.

[edit] Juxtacrine

Juxtacrine signalling Juxtacrine signals are transmitted along cell membranes via protein or lipid components integral to the membrane and are capable of affecting either the emitting cell or cells immediately adjacent.^{[citation needed]}

This section requires expansion.

Diseases of the endocrine system are common,^[3] including conditions such as diabetes mellitus, thyroid disease, and obesity. Endocrine disease is characterized by dysregulated hormone release (a productive pituitary adenoma), inappropriate response to signaling (hypothyroidism), lack of a gland (diabetes mellitus type 1, diminished erythropoiesis in chronic renal failure), or structural enlargement in a critical site such as the testis (toxic multinodular goitre). Hypofunction of endocrine glands can occur as a result of loss of reserve, hyposecretion, agenesis, atrophy, or active destruction. Hyperfunction can occur as a result of hypersecretion, loss of suppression, hyperplastic or neoplastic change, or hyperstimulation.

Endocrinopathies are classified as primary, secondary, or tertiary. Primary endocrine disease inhibits the action of downstream glands. Secondary endocrine disease is indicative of a problem with the pituitary gland. Tertiary endocrine disease is associated with dysfunction of the hypothalamus and its releasing hormones.^{[citation needed]}

As the thyroid, and hormones have been implicated in signaling distant tissues to proliferate, for example, the estrogen receptor has been shown to be involved in certain breast cancers. Endocrine, paracrine, and autocrine signaling have all been implicated in proliferation, one of the required steps of oncogenesis.^[4]

[edit] Table of endocrine glands and secreted hormones

This is a table of the glands of the endocrine system, and their secreted hormones.

[edit] Hypothalamus

Secreted hormone	Abbreviation	Produced by	Effect
Thyrotropin-releasing hormone (Prolactin-releasing hormone)	TRH, TRF, or PRH	Parvocellular neurosecretory neurons	Stimulate thyroid-stimulating hormone (TSH) release from anterior pituitary (primarily) Stimulate prolactin release from anterior pituitary
Dopamine (Prolactin-inhibiting hormone)	DA or PIH	Dopamine neurons of the arcuate nucleus	Inhibit prolactin release from anterior pituitary
Growth hormone-releasing hormone	GHRH	Neuroendocrine neurons of the Arcuate nucleus	Stimulate Growth hormone (GH) release from anterior pituitary
Somatostatin (growth hormone-inhibiting hormone)	SS, GHIH, or SRIF	Neuroendocrine cells of the Periventricular nucleus	Inhibit Growth hormone (GH) release from anterior pituitary Inhibit thyroid-stimulating hormone (TSH) release from anterior pituitary
Gonadotropin-releasing hormone	GnRH or LHRH	Neuroendocrine cells of the Preoptic area	Stimulate follicle-stimulating hormone (FSH) release from anterior pituitary Stimulate luteinizing hormone (LH) release from anterior pituitary
Corticotropin-releasing hormone	CRH or CRF	Parvocellular neurosecretory neurons	Stimulate adrenocorticotropic hormone (ACTH) release from anterior pituitary
Oxytocin		Magnocellular neurosecretory cells	Uterine contraction Lactation (letdown reflex)
Vasopressin (antidiuretic hormone)	ADH or AVP	Parvocellular neurosecretory neurons	Increases water permeability in the distal convoluted tubule and collecting duct of nephrons, thus promoting water reabsorption and increasing blood volume

[edit] Pineal body (epiphysis)

Secreted hormone	From cells	Effect
Melatonin (Primarily)	Pinealocytes	Antioxidant Monitors the circadian rhythm including inducement of drowsiness
Dimethyltryptamine		Speculated role in mystical and dream experiences

[edit] Pituitary Gland (hypophysis)

[edit] Anterior pituitary lobe (adenohypophysis)

Secreted hormone	Abbreviation	From cells	Effect
Growth hormone (somatotropin)	GH	Somatotropes	Stimulates growth and cell reproduction Stimulates Insulin-like growth factor 1 release from liver
Thyroid-stimulating hormone (thyrotropin)	TSH	Thyrotropes	Stimulates thyroxine (T4) and triiodothyronine (T3) synthesis and release from thyroid gland Stimulates iodine absorption by thyroid gland
Adrenocorticotropic hormone (corticotropin)	ACTH	Corticotropes	Stimulates corticosteroid (glucocorticoid and mineralcorticoid) and androgen synthesis and release from adrenocortical cells
Follicle-stimulating hormone	FSH	Gonadotropes	In females: Stimulates maturation of ovarian follicles in ovary In males: Stimulates maturation of seminiferous tubules In males: Stimulates spermatogenesis In males: Stimulates production of androgen-binding protein from Sertoli cells of the testes
Luteinizing hormone	LH	Gonadotropes	In females: Stimulates ovulation In females: Stimulates formation of corpus luteum In males: Stimulates testosterone synthesis from Leydig cells (interstitial cells)
Prolactin	PRL	Lactotropes	Stimulates milk synthesis and release from mammary glands Mediates sexual gratification

[edit] Posterior pituitary lobe (neurohypophysis)

Secreted hormone	Abbreviation	From cells	Effect
Oxytocin		Magnocellular neurosecretory cells	Uterine contraction Lactation (letdown reflex)
Vasopressin (antidiuretic hormone)	ADH or AVP	Parvocellular neurosecretory neurons	Increases water permeability in the distal convoluted tubule and collecting duct of nephrons, thus promoting water reabsorption and increasing blood volume

Oxytocin and anti-diuretic hormone are not secreted in the posterior lobe, merely stored.

[edit] Intermediate pituitary lobe (pars intermedia)

Secreted hormone	Abbreviation	From cells	Effect
Melanocyte-stimulating hormone	MSH	Melanotropes	Stimulates melanin synthesis and release from skin/hair melanocytes

[edit] Thyroid

Secreted hormone	Abbreviation	From cells	Effect
Triiodothyronine	T3	Thyroid epithelial cell	(More potent form of thyroid hormone) Stimulates body oxygen and energy consumption, thereby increasing the basal metabolic rate Stimulates RNA polymerase I and II, thereby promoting protein synthesis
Thyroxine (tetraiodothyronine)	T4	Thyroid epithelial cells	(Less active form of thyroid hormone) (Acts as a prohormone to triiodothyronine) Stimulates body oxygen and energy consumption, thereby increasing the basal metabolic rate Stimulates RNA polymerase I and II, thereby promoting protein synthesis
Calcitonin		Parafollicular cells	Stimulates osteoblasts and thus bone construction Inhibits Ca2+ release from bone, thereby reducing blood Ca2+

[edit] Parathyroid

Secreted hormone	Abbreviation	From cells	Effect
Parathyroid hormone	PTH	Parathyroid chief cell	Calcium: Stimulates Ca2+ release from bone, thereby increasing blood Ca2+ Stimulates osteoclasts, thus breaking down bone Stimulates Ca2+ reabsorption in kidney Stimulates activated vitamin D production in kidney Phosphate: Stimulates PO4= release from bones, thereby increasing blood PO4= Inhibits PO4= reabsorption in kidney, so more PO4= is excreted Overall, small net drop in serum PO4=

[edit] Heart

Secreted hormone	Abbreviation	From cells	Effect
Atrial-natriuretic peptide	ANP	Cardiac myocytes	Reduce blood pressure by: reducing systemic vascular resistance, reducing blood water, sodium and fats
Brain natriuretic peptide	BNP	Cardiac myocytes	(To a lesser degree than ANP) reduce blood pressure by: reducing systemic vascular resistance, reducing blood water, sodium and fats

[edit] Striated muscle

Secreted hormone	From cells	Effect
Thrombopoietin	Myocytes	stimulates megakaryocytes to produce platelets[5]

[edit] Skin

Secreted hormone	From cells	Effect
Calcidiol (25-hydroxyvitamin D3)		Inactive form of Vitamin D3

[edit] Adipose tissue

Secreted hormone	From cells	Effect
Leptin (Primarily)	Adipocytes	decrease of appetite and increase of metabolism.
Estrogens[6] (mainly Estrone)	Adipocytes

[edit] Stomach

Secreted hormone	Abbreviation	From cells	Effect
Gastrin (Primarily)		G cells	Secretion of gastric acid by parietal cells
Ghrelin		P/D1 cells	Stimulate appetite, secretion of growth hormone from anterior pituitary gland
Neuropeptide Y	NPY		increased food intake and decreased physical activity
Somatostatin		D cells	Suppress release of gastrin, cholecystokinin (CCK), secretin, motilin, vasoactive intestinal peptide (VIP), gastric inhibitory polypeptide (GIP), enteroglucagon Lowers rate of gastric emptying Reduces smooth muscle contractions and blood flow within the intestine.[7]
Histamine		ECL cells	stimulate gastric acid secretion
Endothelin		X cells	Smooth muscle contraction of stomach[8]

[edit] Duodenum

Secreted hormone	From cells	Effect
Secretin	S cells	Secretion of bicarbonate from liver, pancreas and duodenal Brunner's glands Enhances effects of cholecystokinin Stops production of gastric juice
Cholecystokinin	I cells	Release of digestive enzymes from pancreas Release of bile from gallbladder hunger suppressant

[edit] Liver

Secreted hormone	Abbreviation	From cells	Effect
Insulin-like growth factor (or somatomedin) (Primarily)	IGF	Hepatocytes	insulin-like effects regulate cell growth and development
Angiotensinogen and angiotensin		Hepatocytes	vasoconstriction release of aldosterone from adrenal cortex dipsogen.
Thrombopoietin		Hepatocytes	stimulates megakaryocytes to produce platelets[5]

[edit] Pancreas

Secreted hormone	From cells	Effect
Insulin (Primarily)	β Islet cells	Intake of glucose, glycogenesis and glycolysis in liver and muscle from blood intake of lipids and synthesis of triglycerides in adipocytes Other anabolic effects
Glucagon (Also Primarily)	α Islet cells	glycogenolysis and gluconeogenesis in liver increases blood glucose level
Somatostatin	δ Islet cells	Inhibit release of insulin[9] Inhibit release of glucagon[9] Suppress the exocrine secretory action of pancreas.
Pancreatic polypeptide	PP cells	Unknown

[edit] Kidney

Secreted hormone	From cells	Effect
Renin (Primarily)	Juxtaglomerular cells	Activates the renin-angiotensin system by producing angiotensin I of angiotensinogen
Erythropoietin (EPO)	Extraglomerular mesangial cells	Stimulate erythrocyte production
Calcitriol (1,25-dihydroxyvitamin D3)		Active form of vitamin D3 Increase absorption of calcium and phosphate from gastrointestinal tract and kidneys inhibit release of PTH
Thrombopoietin		stimulates megakaryocytes to produce platelets[5]

[edit] Adrenal glands

[edit] Adrenal cortex

Secreted hormone	From cells	Effect
Glucocorticoids (chiefly cortisol)	zona fasciculata and zona reticularis cells	Stimulates gluconeogenesis Stimulates fat breakdown in adipose tissue Inhibits protein synthesis Inhibits glucose uptake in muscle and adipose tissue Inhibits immunological responses (immunosuppressive) Inhibits inflammatory responses (anti-inflammatory)
Mineralocorticoids (chiefly aldosterone)	Zona glomerulosa cells	Stimulates active sodium reabsorption in kidneys Stimulates passive water reabsorption in kidneys, thus increasing blood volume and blood pressure Stimulates potassium and H+ secretion into nephron of kidney and subsequent excretion
Androgens (including DHEA and testosterone)	Zona fasciculata and Zona reticularis cells	In males: Relatively small effect compared to androgens from testes In females: masculinizing effects (ie. excessive facial hair)

[edit] Adrenal medulla

Secreted hormone	From cells	Effect
Adrenaline (epinephrine) (Primarily)	Chromaffin cells	Fight-or-flight response: Boost the supply of oxygen and glucose to the brain and muscles (by increasing heart rate and stroke volume, vasodilation, increasing catalysis of glycogen in liver, breakdown of lipids in fat cells) Dilate the pupils Suppress non-emergency bodily processes (e.g., digestion) Suppress immune system
Noradrenaline (norepinephrine)	Chromaffin cells	Fight-or-flight response: Boost the supply of oxygen and glucose to the brain and muscles (by increasing heart rate and stroke volume, vasoconstriction and increased blood pressure, breakdown of lipids in fat cells) Increase skeletal muscle readiness.
Dopamine	Chromaffin cells	Increase heart rate and blood pressure
Enkephalin	Chromaffin cells	Regulate pain

[edit] Testes

Secreted hormone	From cells	Effect
Androgens (chiefly testosterone)	Leydig cells	Anabolic: growth of muscle mass and strength, increased bone density, growth and strength, Virilizing: maturation of sex organs, formation of scrotum, deepening of voice, growth of beard and axillary hair.
Estradiol	Sertoli cells	Prevent apoptosis of germ cells[10]
Inhibin	Sertoli cells	Inhibit production of FSH

[edit] Ovarian follicle / Corpus luteum

Secreted hormone	From cells	Effect
Progesterone	Granulosa cells, theca cells	Support pregnancy[11]: Convert endometrium to secretory stage Make cervical mucus permeable to sperm. Inhibit immune response, e.g., towards the human embryo Decrease uterine smooth muscle contractility[11] Inhibit lactation Inhibit onset of labor. Other: Raise epidermal growth factor-1 levels Increase core temperature during ovulation[12] Reduce spasm and relax smooth muscle (widen bronchi and regulate mucus) Anti-inflammatory Reduce gall-bladder activity[13] Normalize blood clotting and vascular tone, zinc and copper levels, cell oxygen levels, and use of fat stores for energy Assist in thyroid function and bone growth by osteoblasts Increase resilience in bone, teeth, gums, joint, tendon, ligament, and skin Promote healing by regulating collagen Provide nerve function and healing by regulating myelin Prevent endometrial cancer by regulating effects of estrogen
Androstenedione	Theca cells	Substrate for estrogen
Estrogens (mainly estradiol)	Granulosa cells	Structural: Promote formation of female secondary sex characteristics Accelerate height growth Accelerate metabolism (burn fat) Reduce muscle mass Stimulate endometrial growth Increase uterine growth Maintain blood vessels and skin Reduce bone resorption, increase bone formation Protein synthesis: Increase hepatic production of binding proteins Coagulation: Increase circulating level of factors 2, 7, 9, 10, antithrombin III, plasminogen Increase platelet adhesiveness Increase HDL, triglyceride, height growth Decrease LDL, fat deposition Fluid balance: Regulate salt (sodium) and water retention Increase growth hormone Increase cortisol, SHBG Gastrointestinal tract: Reduce bowel motility Increase cholesterol in bile Melanin: Increase pheomelanin, reduce eumelanin Cancer: Support hormone-sensitive breast cancers [14] (Suppression of production in the body of estrogen is a treatment for these cancers.) Lung function: Promote lung function by supporting alveoli.[15]
Inhibin	Granulosa cells	Inhibit production of FSH from anterior pituitary

[edit] Placenta (when pregnant)

Secreted hormone	Abbreviation	From cells	Effect
Progesterone (Primarily)			Support pregnancy[11]: Inhibit immune response, towards the fetus. Decrease uterine smooth muscle contractility[11] Inhibit lactation Inhibit onset of labor. Support fetal production of adrenal mineralo- and glucosteroids. Other effects on mother similar to ovarian follicle-progesterone
Estrogens (mainly Estriol) (Also Primarily)			Effects on mother similar to ovarian follicle estrogen
Human chorionic gonadotropin	HCG	Syncytiotrophoblast	promote maintenance of corpus luteum during beginning of pregnancy Inhibit immune response, towards the human embryo.
Human placental lactogen	HPL	Syncytiotrophoblast	increase production of insulin and IGF-1 increase insulin resistance and carbohydrate intolerance
Inhibin		Fetal Trophoblasts	suppress FSH

[edit] Uterus (when pregnant)

Secreted hormone	Abbreviation	From cells	Effect
Prolactin	PRL	Decidual cells	milk production in mammary glands
Relaxin		Decidual cells	Unclear in humans and animals

[edit] See also

• Releasing hormones
• Neuroendocrinology
• Nervous system
• Endocrine disruptor
• Major systems of the human body
• Endocrine disease
• Endocrinology

[edit] References

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