Endocrine system

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 Role in disease

3 Table of endocrine glands and secreted hormones

3.1 Hypothalamus

3.2 Pineal body (epiphysis)

3.3 Pituitary gland (hypophysis)

3.3.1 Anterior pituitary lobe (adenohypophysis)

3.3.2 Posterior pituitary lobe (neurohypophysis)

3.3.3 Intermediate pituitary lobe (pars intermedia)

3.4 Thyroid

3.5 Parathyroid

3.6 Heart

3.7 Striated muscle

3.8 Skin

3.9 Adipose tissue

3.10 Stomach

3.11 Duodenum

3.12 Liver

3.13 Pancreas

3.14 Kidney

3.15 Adrenal glands

3.15.1 Adrenal cortex

3.15.2 Adrenal medulla

3.15.3 Testes

3.16 Ovary

3.17 Placenta (when pregnant)

3.18 Uterus (when pregnant)

4 See also

5 References

6 External links

The endocrine system is a system of small organs that involve the
release of extracellular signaling molecules known as hormones. The
endocrine system is instrumental in regulating metabolism, growth,
development and puberty, and tissue function 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.

Major endocrine glands. (Male on the left, female on the right.) 1.
Pineal gland 2. Pituitary gland 3. Thyroid gland 4. Thymus 5. Adrenal
gland 6. Pancreas 7. Ovary 8. Testes

Function

The endocrine system is an information signal system much like the
nervous system. However, the nervous system uses nerves to conduct
information, whereas the endocrine system mainly uses blood vessels as
information channels. Glands located in many regions of the body release
into the bloodstream specific chemical messengers called hormones.
Hormones regulate the many and varied functions of an organism, e.g.,
mood, growth and development, tissue function, and metabolism, as well
as sending messages and acting on them.

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.

Endocrine

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.

Autocrine

Other signaling can target the same cell.

Paracrine

Paracrine signaling is where the target cell is nearby.

Juxtacrine

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.

Role in disease

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 or destruction of a gland (diabetes mellitus type
1, diminished erythropoiesis in chronic renal failure), or structural
enlargement in a critical site such as the neck (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.
Tertiary endocrine disease is associated with dysfunction of the
hypothalamus and its releasing hormones.

Cancer can occur in endocrine glands, such 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]

Table of endocrine glands and secreted hormones

Hypothalamus

Secreted hormone Abbreviation From cells Effect

Thyrotropin-releasing hormone TRH Parvocellular neurosecretory neurons
Release thyroid-stimulating hormone from anterior pituitary (primarily)

Stimulate prolactin release from anterior pituitary.

Gonadotropin-releasing hormone GnRH Neuroendocine cells of the Preoptic
area Release of FSH and LH from anterior pituitary.

Growth hormone-releasing hormone GHRH Neuroendocrine neurons of the
Arcuate nucleus Release GH from anterior pituitary

Corticotropin-releasing hormone CRH Parvocellular neurosecretory neurons
Release ACTH from anterior pituitary

Oxytocin

Magnocellular neurosecretory cells Contraction of cervix and vagina

Involved in orgasm, trust between people.[5] and circadian homeostasis
(body temperature, activity level, wakefulness).[6] release breast milk

Vasopressin ADH or AVP Parvocellular neurosecretory neurons Increases
permeability of distal convoluted tubule and collecting duct to water in
the nephrons of the kidney, thus increasing water reabsorbtion.

Somatostatin, also growth hormone-inhibiting hormone SS or GHIH
Neuroendocrine cells of the Periventricular nucleus Inhibit release of
GH and TSH from anterior pituitary

Prolactin inhibiting hormone or Dopamine PIH or DA Dopamine neurons of
the arcuate nucleus Inhibit release of prolactin and TSH from anterior
pituitary

Prolactin-releasing hormone PRH

Release prolactin from anterior pituitary

Pineal body (epiphysis)

Secreted hormone From cells Effect

Melatonin (Primarily) Pinealocytes antioxidant and causes drowsiness

Pituitary gland (hypophysis)

Anterior pituitary lobe (adenohypophysis)

Secreted hormone Abbreviation From cells Effect

Growth hormone GH Somatotropes stimulates growth and cell reproduction

Release Insulin-like growth factor 1 from liver

Prolactin PRL Lactotropes milk production in mammary glands

sexual gratification after sexual acts

Adrenocorticotropic hormone or corticotropin ACTH Corticotropes
synthesis of corticosteroids (glucocorticoids and androgens) in
adrenocortical cells

Lipotropin

Corticotropes lipolysis and steroidogenesis,

stimulates melanocytes to produce melanin

Thyroid-stimulating hormone or thyrotropin TSH Thyrotropes stimulates
thyroid gland to secrete thyroxine (T4) and triiodothyronine (T3)

Follicle-stimulating hormone FSH Gonadotropes In female: stimulates
maturation of Graafian follicles in ovary.

In male: spermatogenesis, enhances production of androgen-binding
protein by the Sertoli cells of the testes

Luteinizing hormone LH Gonadotropes In female: ovulation

In male: stimulates Leydig cell production of testosterone

Posterior pituitary lobe (neurohypophysis)

f ing Secreted hormone Abbreviation From cells Effect

Oxytocin

Magnocellular neurosecretory cells Contraction of cervix and vagina

Involved in orgasm, trust between people.[5] and circadian homeostasis
(body temperature, activity level, wakefulness).[6] release breast milk

Vasopressin or antidiuretic hormone AVP or ADH Magnocellular
neurosecretory cells retention of water in kidneys

moderate vasoconstriction

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

Intermediate pituitary lobe (pars intermedia)

Secreted hormone Abbreviation From cells Effect

Melanocyte-stimulating hormone MSH Melanotroph melanogenesis by
melanocytes in skin and hair.

Thyroid

Secreted hormone Abbreviation From cells Effect

Triiodothyronine T3 Thyroid epithelial cell potent form of thyroid
hormone: increase the basal metabolic rate & sensitivity to
catecholamines,

affect protein synthesis

Thyroxine or tetraiodothyronine T4 Thyroid epithelial cells less active
form of thyroid hormone: increase the basal metabolic rate & sensitivity
to catecholamines,

affect protein synthesis, often functions as a prohormone

Calcitonin

Parafollicular cells Construct bone

reduce blood Ca2+

Parathyroid

Secreted hormone Abbreviation From cells Effect

Parathyroid hormone PTH Parathyroid chief cell increase blood Ca2+:
*indirectly stimulate osteoclasts

Ca2+ reabsorption in kidney

activate vitamin D

(Slightly) decrease blood phosphate:

decreased reuptake in kidney but increased uptake from bones

activate vitamin D

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

Striated muscle

Secreted hormone From cells Effect

Thrombopoietin Myocytes stimulates megakaryocytes to produce
platelets[7]

Skin

Secreted hormone From cells Effect

Calcidiol (25-hydroxyvitamin D3)

Inactive form of Vitamin D3

Adipose tissue

Secreted hormone From cells Effect

Leptin (Primarily) Adipocytes decrease of appetite and increase of
metabolism.

Estrogens[8] (mainly Estrone) Adipocytes

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

Secretin

S cells Secretion of bicarbonate from liver, pancreas and duodenal
Brunner’s glands

Enhances effects of cholecystokinin Stops production of gastric juice

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.[9]

Histamine

ECL cells stimulate gastric acid secretion

Endothelin

X cells Smooth muscle contraction of stomach[10]

Duodenum

Secreted hormone From cells Effect

Cholecystokinin I cells Release of digestive enzymes from pancreas

Release of bile from gallbladder hunger suppressant

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[7]

Pancreas

Secreted hormone From cells Effect

Insulin (Primarily) ss 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) a Islet cells glycogenolysis and
gluconeogenesis in liver

increases blood glucose level

Somatostatin d Islet cells Inhibit release of insulin[11]

Inhibit release of glucagon[11] Suppress the exocrine secretory action
of pancreas.

Pancreatic polypeptide PP cells Unknown

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[7]

Adrenal glands

Adrenal cortex

Secreted hormone From cells Effect

Glucocorticoids (chiefly cortisol) zona fasciculata and zona reticularis
cells Stimulation of gluconeogenesis

Inhibition of glucose uptake in muscle and adipose tissue Mobilization
of amino acids from extrahepatic tissues Stimulation of fat breakdown in
adipose tissue anti-inflammatory and immunosuppressive

Mineralocorticoids (chiefly aldosterone) Zona glomerulosa cells Increase
blood volume by reabsorption of sodium in kidneys (primarily)

Potassium and H+ secretion in kidney.

Androgens (including DHEA and testosterone) Zona fasciculata and Zona
reticularis cells Virilization, anabolic

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

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[12]

Inhibin Sertoli cells | Inhibit production of FSH

Ovary

These originate either from the ovarian follicle or the corpus luteum.

Secreted hormone From cells Effect

Progesterone Granulosa cells, theca cells Support pregnancy[13]:

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[13]

Inhibit lactation

Inhibit onset of labor.

Other:

Raise epidermal growth factor-1 levels

Increase core temperature during ovulation[14]

Reduce spasm and relax smooth muscle (widen bronchi and regulate mucus)

Anti-inflammatory

Reduce gall-bladder activity[15]

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 [16] (Suppression of production
in the body of estrogen is a treatment for these cancers.)

Lung function:

Promote lung function by supporting alveoli.[17]

Inhibin Granulosa cells Inhibit production of FSH from anterior
pituitary

Placenta (when pregnant)

Secreted hormone Abbreviation From cells Effect

Progesterone (Primarily)

Support pregnancy[13]:

Inhibit immune response, towards the fetus.

Decrease uterine smooth muscle contractility[13]

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

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

References

^ Collier, Judith. et.al (2006). Oxford Handbook of Clinical Specialties
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^ University of Virginia — HISTOLOGY OF THE ENDOCRINE GLANDS

^ Kasper et al. (2005). Harrison’s Principles of Internal Medicine.
McGraw Hill. pp. 2074. ISBN 0-07-139140-1. 

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http://www.iew.unizh.ch/home/kosfeld/papers/ottrust_nature.pdf. 

^ a b Kraft U (Jun/July 2007). «Rhythm and Blues». Scientific American
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http://www.sciamdigital.com/index.cfm?fa=Products.ViewIssuePreview&ARTIC
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^ a b c Kaushansky K (May 2006). «Lineage-specific hematopoietic growth
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^ Fruehbeck G (July 2004). «The adipose tissue as a source of vasoactive
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^ Colorado State University — Biomedical Hypertextbooks — Somatostatin

^ Endo K, Matsumoto T, Kobayashi T, Kasuya Y, Kamata K (February 2005).
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http://joi.jlc.jst.go.jp/JST.JSTAGE/jsmr/41.35?from=PubMed. 

^ a b Physiology at MCG 5/5ch4/s5ch4_17

^ Pentikaeinen V, Erkkilae K, Suomalainen L, Parvinen M, Dunkel L (May
2000). «Estradiol acts as a germ cell survival factor in the human
testis in vitro». J Clin Endocrinol Metab. 85 (5): 2057–67.
doi:10.1210/jc.85.5.2057. PMID 10843196.
http://jcem.endojournals.org/cgi/pmidlookup?view=long&pmid=10843196. 

^ a b c d Placental Hormones

^ Physiology at MCG 5/5ch9/s5ch9_13

^ Hould F, Fried G, Fazekas A, Tremblay S, Mersereau W (1988).
«Progesterone receptors regulate gallbladder motility». J Surg Res 45
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^ Hormonal Therapy

^ Massaro D, Massaro GD (2004). «Estrogen regulates pulmonary alveolar
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http://en.wikipedia.org/wiki/Endocrine_system

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