Endocrinology

Our body is a whole human structure that consists of different parts with their different functions that plays a very important role in our everyday lives. As we go on, you'll see this blog containing facts about the major system in our body.

Introduction of Endocrinology

   Endocrine System is a special system in our body which secretes different hormones directly in bloodstream that helps in the regulation in our body. On the other hand, it has also a counterpart system which also known as the Exocrine system wherein it secretes it chemicals via ducts. As Endocrine is termed as the major system in our body, it serves as the information system and works very fast. It has also effects in our body but slow to initiate.

    The chemicals or the substances that released by the endocrine glands are called Hormones which function is to travel and target the bloodstream to regulate responses. This hormones have different functions that helps our body to grow and develop, it also helps in the metabolism, functions of our tissues and many other.

    Endocrine system is made up of series of glands which produces different substances also known as Hormones which has different jobs to do in our body. 

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Endocrine System: How it Works

Video Credit: http://www.youtube.com/watch?v=YI2qYRWzSZ4

Endocrine System and the Hormone secreted

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Hypothalamus

Secreted hormone	Abbreviation	Produced by	Effect
Thyrotropin-releasing hormone	TRH	Parvocellular neurosecretory neurons	Stimulate thyroid-stimulating hormone (TSH) released from anterior pituitary (primarily)
Dopamine (Prolactin-inhibiting hormone)	DA or PIH	Dopamine neurons of the arcuate nucleus	Inhibit prolactin released from anterior pituitary
Growth hormone-releasing hormone	GHRH	Neuroendocrine neurons of theArcuate nucleus	Stimulate Growth hormone (GH) release from anterior pituitary
Somatostatin (growth hormone-inhibiting hormone)	SS, GHIH, or SRIF	Neuroendocrine cells of thePeriventricular 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 thePreoptic 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 of the Paraventricular Nucleus	Stimulate adrenocorticotropic hormone (ACTH) release from anterior pituitary
Oxytocin	OT or OXT	Magnocellular neurosecretory neurons of the Supraoptic nucleusand Paraventricular nucleus	Uterine contraction Lactation (letdown reflex)
Vasopressin (antidiuretic hormone)	ADH or AVP or VP	Parvocellular neurosecretory neurons, Magnocellular neurosecretory neurons of theParaventricular nucleus andSupraoptic nucleus	Increases water permeability in the distal convoluted tubule and collecting duct of nephrons, thus promoting water reabsorption and increasing blood volume

Pineal body (epiphysis)

Secreted hormone	From cells	Effect
Melatonin	Pinealocytes	Antioxidant Monitors the circadian rhythm including inducement of drowsiness and lowering of the middle body temperature sleep cycle

Pituitary gland (hypophysis)

Anterior pituitary lobe (adenohypophysis)

Secreted hormone	Abbreviation	From cells	Effect
Growth hormone (somatotropin)	GH	Somatotrophs	Stimulates growth and cell reproduction Stimulates Insulin-like growth factor 1 release from liver
Thyroid-stimulating hormone (thyrotropin)	TSH	Thyrotrophs	Stimulates thyroxine (T4) and triiodothyronine (T3) synthesis and release from thyroid gland Stimulates iodine absorption by thyroid gland
Adrenocorticotropic hormone (corticotropin)	ACTH	Corticotrophs	Stimulates corticosteroid (glucocorticoid and mineralcorticoid) and androgen synthesis and release from adrenocortical cells
Beta-endorphin	-	Corticotrophs	Inhibits perception of pain
Follicle-stimulating hormone	FSH	Gonadotrophs	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	Gonadotrophs	In females: Stimulates ovulation In females: Stimulates formation of corpus luteum In males: Stimulates testosterone synthesis from Leydig cells (interstitial cells)
Prolactin	PRL	Lactotrophs	Stimulates milk synthesis and release from mammary glands Mediates sexual gratification
Melanocyte-stimulating hormone	MSH	Melanotropes in the Pars intermedia of the Anterior Pituitary	Stimulates melanin synthesis and release from skin/hair melanocytes

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.

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+

Alimentary system

Photo Credit: http://en.wikipedia.org/wiki/File:Endocrine_Alimentary_system_en.svg

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. It can be associated with obesity.
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.
Histamine		ECL cells	stimulate gastric acid secretion
Endothelin		X cells	Smooth muscle contraction of stomach

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

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

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 Inhibit release of glucagon Suppress the exocrine secretory action of pancreas.
Pancreatic polypeptide	PP cells	Self regulate the pancreas secretion activities and effect the hepatic glycogen levels.

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 ofPTH
Thrombopoietin		stimulates megakaryocytes to produce platelets

Adrenal glands

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

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

Reproductive

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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 andaxillary hair.
Estradiol	Sertoli cells	Prevent apoptosis of germ cells
Inhibin	Sertoli cells	Inhibit production of FSH

Ovarian follicle and corpus luteum

Secreted hormone	From cells	Effect
Progesterone	Granulosa cells, theca cells	Support pregnancy: Convert endometrium to secretory stage Make cervical mucus thick and impenetrable to sperm. Inhibit immune response, e.g., towards the human embryo Decrease uterine smooth muscle contractility Inhibit lactation Inhibit onset of labor. Other: Raise epidermal growth factor-1 levels Increase core temperature during ovulation Reduce spasm and relax smooth muscle (widen bronchi and regulate mucus) Anti-inflammatory Reduce gall-bladder activity 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(Suppression of production in the body of estrogen is a treatment for these cancers.) Lung function: Promote lung function by supporting alveoli.
Inhibin	Granulosa cells	Inhibit production of FSH from anterior pituitary

Placenta (when pregnant)

Secreted hormone	Abbreviation	From cells	Effect
Progesterone (Primarily)			Support pregnancy: Inhibit immune response, towards the fetus. Decrease uterine smooth muscle contractility 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

Calcium regulation

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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 PO3-4 release from bones, thereby increasing blood PO3-4. Inhibits PO3-4 reabsorption in kidney, so more PO3-4 is excreted Overall, small net drop in serum PO3-4.

Skin

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

Miscellaneous

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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

Bone marrow

Secreted hormone	From cells	Effect
Thrombopoietin	liver and kidney cells	stimulates megakaryocytes to produce platelets

Adipose tissue

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

Major endocrine systems

The human endocrine system consists of several systems that operate via feedback loops. Several important feedback systems are mediated via the hypothalamus and pituitary.

• TRH - TSH - T3/T4
• GnRH - LH/FSH - sex hormones
• CRH - ACTH - cortisol
• Renin - angiotensin - aldosterone

Table Credit: http://upload.wikimedia.org/wikipedia/commons/4/43/Endocrine_miscelaneous_en.svg