Endocrine system

The endocrine system is made up of glands that produce and secrete hormones, chemical substances produced in the body that regulate the activity of cells or organs. These hormones regulate the body’s growth, metabolism (the physical and chemical processes of the body), and sexual development and function.Image result for endocrine systemThe endocrine system refers to the collection of glands of an organism that secrete hormones directly into the circulatory system to be carried towards distant target organs. The major endocrine glands include the pineal glandpituitary glandpancreasovariestestesthyroid glandparathyroid gland,hypothalamusgastrointestinal tract and adrenal glands. The endocrine system is in contrast to the exocrine system, which secretes its hormones to the outside of the body using ducts. The endocrine system is an information signal system like the nervous system, yet its effects and mechanism are classifiably different. The endocrine system’s effects are slow to initiate, and prolonged in their response, lasting from a few hours up to weeks. The nervous system sends information very quickly, and responses are generally short lived. In vertebrates, the hypothalamus is the neural control center for all endocrine systems. The field of study dealing with the endocrine system and its disorders is endocrinology, a branch of internal medicine.[1] Special features ofendocrine glands are, in general, their ductless nature, their vascularity, and commonly the presence of intracellular vacuoles or granules that store their hormones. In contrast, exocrine glands, such as salivary glandssweat glands, and glands within the gastrointestinal tract, tend to be much less vascular and have ducts or a hollow lumen.

In addition to the specialized endocrine organs mentioned above, many other organs that are part of other body systems, such as bonekidneyliverheartand gonads, have secondary endocrine functions. For example, the kidney secretes endocrine hormones such as erythropoietin and renin. Hormones can consist of either amino acid complexes, steroidseicosanoidsleukotrienes, or prostaglandins.[1]The major glands that make up the human endocrine system include the:

  • hypothalamus
  • pituitary gland
  • thyroid
  • parathyroids
  • adrenal glands
  • pineal body
  • reproductive glands (which include the ovaries and testes)
  • pancreas

Endocrine organs and known secreted hormones

Endocrine glands in the human head and neck and their hormones


Secreted hormoneAbbreviationProduced byEffect
Thyrotropin-releasing hormoneTRHParvocellular neurosecretory neuronsStimulate thyroid-stimulating hormone (TSH) release from anterior pituitary (primarily)
(Prolactin-inhibiting hormone)
DA or PIHDopamine neurons of the arcuate nucleusInhibit prolactin released from anterior pituitary
Growth hormone-releasing hormoneGHRHNeuroendocrine neurons of theArcuate nucleusStimulate Growth hormone (GH) release from anterior pituitary
(growth hormone-inhibiting hormone)
SS, GHIH, or SRIFNeuroendocrine cells of thePeriventricular nucleusInhibit Growth hormone (GH) release from anterior pituitary
Inhibit thyroid-stimulating hormone (TSH) release from anterior pituitary
Gonadotropin-releasing hormoneGnRH or LHRHNeuroendocrine cells of thePreoptic areaStimulate follicle-stimulating hormone (FSH) release from anterior pituitary
Stimulate luteinizing hormone (LH) release from anterior pituitary
Corticotropin-releasing hormoneCRH or CRFParvocellular neurosecretory neurons of the Paraventricular NucleusStimulate adrenocorticotropic hormone (ACTH) release from anterior pituitary
(antidiuretic hormone)
ADH or AVP or VPParvocellular neurosecretory neuronsMagnocellular neurosecretory neurons of theParaventricular nucleus andSupraoptic nucleusIncreases water permeability in the distal convoluted tubule and collecting duct of nephrons, thus promoting water reabsorption and increasing blood volume

Pineal body (epiphysis)

Secreted hormoneFrom cellsEffect
Monitors the circadian rhythm including induction of drowsiness and lowering of the core body temperature

Pituitary gland (hypophysis)

The pituitary gland (or hypophysis) is an endocrine gland about the size of a pea and weighing 0.5 grams (0.018 oz) in humans. It is a protrusion off the bottom of the hypothalamus at the base of thebrain, and rests in a small, bony cavity (sella turcica) covered by a dural fold (diaphragma sellae). The pituitary is functionally connected to the hypothalamus by the median eminence via a small tube called the infundibular stem or pituitary stalk. .[citation needed]

Anterior pituitary lobe (adenohypophysis)

Secreted hormoneAbbreviationFrom cellsEffect
Growth hormone
GHSomatotrophsStimulates growth and cell reproduction
Stimulates Insulin-like growth factor 1 release from liver
Thyroid-stimulating hormone
TSHThyrotrophsStimulates thyroxine (T4) and triiodothyronine (T3) synthesis and release from thyroid gland
Stimulates iodine absorption by thyroid gland
Adrenocorticotropic hormone
ACTHCorticotrophsStimulates corticosteroid (glucocorticoid and mineralcorticoid) and androgen synthesis and release from adrenocortical cells
Beta-endorphinCorticotrophsInhibits perception of pain
Follicle-stimulating hormoneFSHGonadotrophsIn 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 hormoneLHGonadotrophsIn females: Stimulates ovulation
In females: Stimulates formation of corpus luteum
In males: Stimulates testosterone synthesis from Leydig cells (interstitial cells)
ProlactinPRLLactotrophsStimulates milk synthesis and release from mammary glands
Mediates sexual gratification
Melanocyte-stimulating hormoneMSHMelanotropes in the Pars intermedia of the Anterior PituitaryStimulates melanin synthesis and release from skin/hair melanocytes

Posterior pituitary lobe (neurohypophysis)

Stored hormoneAbbreviationFrom cellsEffect
Oxytocin Magnocellular neurosecretory cellsIn females: uterine contraction during birthing, lactation (letdown reflex) when nursing
(antidiuretic hormone)
ADH or AVPParvocellular neurosecretory neuronsIncreases 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.


Secreted hormoneAbbreviationFrom cellsEffect
TriiodothyronineT3Thyroid 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
T4Thyroid 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 cellsStimulates osteoblasts and thus bone construction
Inhibits Ca2+ release from bone, thereby reducing blood Ca2+

Digestive system

Endocrine Alimentary system en.svg


Secreted hormoneAbbreviationFrom cellsEffect
Gastrin (Primarily) G cellsSecretion of gastric acid by parietal cells
Ghrelin P/D1 cellsStimulate appetite.
Neuropeptide YNPY Increased food intake and decreased physical activity. It can be associated with obesity.
Somatostatin D cellsSuppress release of gastrincholecystokinin (CCK), secretinmotilinvasoactive intestinal peptide(VIP), gastric inhibitory polypeptide (GIP), enteroglucagon

Lowers rate of gastric emptying

Reduces smooth muscle contractions and blood flow within the intestine.[2]

Histamine ECL cellsstimulate gastric acid secretion
Endothelin X cellsSmooth muscle contraction of stomach[3]

Duodenum (small intestine)

Secreted hormoneFrom cellsEffect
SecretinS cellsSecretion of bicarbonate from liverpancreas and duodenal Brunner’s glands

Enhances effects of cholecystokinin, stops production of gastric juice

CholecystokininI cellsRelease of digestive enzymes from pancreas

Release of bile from gallbladderhunger suppressant


Secreted hormoneAbbreviationFrom cellsEffect
Insulin-like growth factor (or somatomedin) (Primarily)IGFHepatocytesinsulin-like effects

regulate cell growth and development

Angiotensinogen and angiotensin Hepatocytesvasoconstriction

release of aldosterone from adrenal cortex dipsogen.

ThrombopoietinTHPOHepatocytesstimulates megakaryocytes to produce platelets[4]
Hepcidin Hepatocytesinhibits intestinal iron absorption and iron release by macrophages


The pancreas is a mixocrine gland and it secretes both enzymes and hormones.

Secreted hormoneFrom cellsEffect
Insulin (Primarily)? Islet cellsIntake of glucoseglycogenesis and glycolysis in liver and muscle from blood.

Intake of lipids and synthesis of triglycerides in adipocytes. Other anabolic effects

Glucagon (Also Primarily)? Islet cellsGlycogenolysis and gluconeogenesis in liver.

Increases blood glucose level.

Somatostatin? Islet cellsInhibit release of insulin[5]

Inhibit release of glucagon[5] Suppress the exocrine secretory action of pancreas.

Pancreatic polypeptidePP cellsSelf regulate the pancreas secretion activities and effect the hepatic glycogen levels.


Secreted hormoneFrom cellsEffect
Renin (Primarily)Juxtaglomerular cellsActivates the renin-angiotensin system by producing angiotensin I of angiotensinogen
Erythropoietin (EPO)Extraglomerular mesangial cellsStimulate erythrocyte production
Calcitriol (1,25-dihydroxyvitamin D3)Proximal tubule cellsActive 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[4]

Adrenal glands

Adrenal cortex

Secreted hormoneFrom cellsEffect
Glucocorticoids (chiefly cortisol)zona fasciculata and zona reticularis cellsStimulates 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 cellsStimulates 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 andtestosterone)Zona fasciculata and Zona reticularis cellsIn males: Relatively small effect compared to androgens from testes
In females: masculinizing effects

Adrenal medulla

Secreted hormoneFrom cellsEffect
Adrenaline (epinephrine) (Primarily)Chromaffin cellsFight-or-flight response:
Noradrenaline (norepinephrine)Chromaffin cellsFight-or-flight response:
DopamineChromaffin cellsIncrease heart rate and blood pressure
EnkephalinChromaffin cellsRegulate pain


Endocrine reproductive system en.svg


Secreted hormoneFrom cellsEffect
Androgens (chiefly testosterone)Leydig cellsAnabolic: growth of muscle mass and strength, increased bone density, growth and strength,

Virilizingmaturation of sex organs, formation of scrotum, deepening of voice, growth of beard andaxillary hair.

EstradiolSertoli cellsPrevent apoptosis of germ cells[6]
InhibinSertoli cellsInhibit production of FSH

Ovarian follicle and corpus luteum

Secreted hormoneFrom cellsEffect
ProgesteroneGranulosa cellstheca cellsSupport pregnancy:[7]



AndrostenedioneTheca cellsSubstrate for estrogen
Estrogens (mainly estradiol)Granulosa cellsStructural:

Protein synthesis:

  • Increase hepatic production of binding proteins


Fluid balance:

Gastrointestinal tract:

  • Reduce bowel motility
  • Increase cholesterol in bile



Lung function:

InhibinGranulosa cellsInhibit production of FSH from anterior pituitary

Placenta (when pregnant)

Secreted hormoneAbbreviationFrom cellsEffect
Progesterone (Primarily)  Support pregnancy:[7]

Other effects on mother similar to ovarian follicle-progesterone

Estrogens (mainly Estriol) (Also Primarily)  Effects on mother similar to ovarian follicle estrogen
Human chorionic gonadotropinHCGSyncytiotrophoblastPromote maintenance of corpus luteum during beginning of pregnancy

Inhibit immune response, towards the human embryo.

Human placental lactogenHPLSyncytiotrophoblastIncrease production of insulin and IGF-1

Increase insulin resistance and carbohydrate intolerance

Inhibin Fetal TrophoblastsSuppress FSH

Uterus (when pregnant)

Secreted hormoneAbbreviationFrom cellsEffect
ProlactinPRLDecidual cellsmilk production in mammary glands
Relaxin Decidual cellsUnclear in humans and animals

Calcium regulation

  • Endocrine caclcium en.svg
  • Calcium regulation.png


Secreted hormoneAbbreviationFrom cellsEffect
Parathyroid hormonePTHParathyroid chief cellCalcium:
  • 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


  • 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.


Secreted hormoneFrom cellsEffect
Calcidiol (25-hydroxyvitamin D3) Inactive form of vitamin D3


Endocrine miscelaneous en.svg


Secreted hormoneAbbreviationFrom cellsEffect
Atrial-natriuretic peptideANPCardiac myocytesReduce blood pressure by:

reducing systemic vascular resistance, reducing blood water, sodium and fats

Brain natriuretic peptideBNPCardiac myocytes(To a lesser degree than ANP) reduce blood pressure by:

reducing systemic vascular resistance, reducing blood water, sodium and fats

Bone marrow

Secreted hormoneFrom cellsEffect
Thrombopoietinliver and kidney cellsstimulates megakaryocytes to produce platelets[4]

Skeletal muscle

In 1998, skeletal muscle was identified as an endocrine organ[12] due to its now well-established role in the secretion of myokines.[12][13] The use of the term myokine to describe cytokines and other peptides produced by muscle as signalling molecules was proposed in 2003.[14]

Adipose tissue

Signalling molecules released by adipose tissue are referred to as adipokines.

Secreted hormoneFrom cellsEffect
Leptin (Primarily)Adipocytesdecrease of appetite and increase of metabolism.
Estrogens[15] (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.[16]


Interaction with immune system

Extensive bidirectional interactions exist between the endocrine system and the immune system.[17] Cortisol has major immunosuppressive effects,[18][19] and dopamine has immunomodulatory functions.[20] On the other hand, cytokines produced during inflammation activate the HPA axis at all three levels, sensible to negative feedback.[21] Moreover, cytokines stimulate hepcidin release from the liver, which is eventually responsible for the anemia of chronic disease.[22]

Other types of signalling

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. Purely neurocrine signaling between neurons, on the other hand, belongs completely to the nervous system.


Autocrine signaling is a form of signaling in which a cell secretes a hormone or chemical messenger (called the autocrine agent) that binds to autocrine receptors on the same cell, leading to changes in the cells.


Some endocrinologists and clinicians include the paracrine system as part of the endocrine system, but there is not consensus. Paracrines are slower acting, targeting cells in the same tissue or organ. An example of this is somatostatin which is released by some pancreatic cells and targets other pancreatic cells.[1]


Juxtacrine signaling is a type of intercellular communication that is transmitted via oligosaccharide, lipid, or protein components of a cell membrane, and may affect either the emitting cell or the immediately adjacent cells.[citation needed]

It occurs between adjacent cells that possess broad patches of closely opposed plasma membrane linked by transmembrane channels known as connexons. The gap between the cells can usually be between only 2 and 4 nm.[citation needed]


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]Diseases of the endocrine system are common,[24] including conditions such as diabetes mellitusthyroid disease, and obesity. Endocrine disease is characterized by irregulated 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 thyroid (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.

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 onco

Diseases of the endocrine system

Hormone levels that are too high or too low indicate a problem with the endocrine system. Hormone diseases also occur if your body does not respond to hormones in the appropriate ways. Stress, infection, and changes in the blood’s fluid and electrolyte balance can also influence hormone levels, according to the National Institutes of Health.

The most common endocrine disease in the United States is diabetes, a condition in which the body does not properly process glucose, a simple sugar. This is due to the lack of insulin or, if the body is producing insulin, because the body is not working effectively, according to Dr. Jennifer Loh, chief of the department of endocrinology for Kaiser Permanente in Hawaii.

Hormone imbalances can have a significant impact on the reproductive system, particularly in women, Loh explained.  

Another disorder, hypothyroidism, occurs when the thyroid gland does not produce enough thyroid hormone to meet the body’s needs. Loh noted that insufficient thyroid hormone can cause many of the body’s functions to slow or shut down completely.

Thyroid cancer begins in the thyroid gland and starts when the cells in the thyroid begin to change, grow uncontrollably and eventually form a tumor, according to Loh.

Hypoglycemia, also called low blood glucose or low blood sugar, occurs when blood glucose drops below normal levels. This typically happens as a result of treatment for diabetes when too much insulin is taken. While Loh noted that the condition can occur in people not undergoing treatment for diabetes, such an occurrence is fairly rare.

  • hypothalamus
  • pituitary gland
  • thyroid
  • parathyroids
  • adrenal glands
  • pineal body
  • reproductive glands (which include the ovaries and testes)
  • pancreas


    The hypothalamus (pronounced: hi-po-THAL-uh-mus), a collection of specialized cells that is located in the lower central part of the brain, is the main link between the endocrine and nervous systems. Nerve cells in the hypothalamus control the pituitary gland by producing chemicals that either stimulate or suppress hormone secretions from the pituitary.


    Although it is no bigger than a pea, the pituitary (pronounced: puh-TOO-uh-ter-ee) gland, located at the base of the brain just beneath the hypothalamus, is considered the most important part of the endocrine system. It’s often called the “master gland” because it makes hormones that control several other endocrine glands.

    The production and secretion of pituitary hormones can be influenced by factors such as emotions and changes in the seasons. To accomplish this, the hypothalamus provides information sensed by the brain (such as environmental temperature, light exposure patterns, and feelings) to the pituitary.

    The tiny pituitary is divided into two parts: the anterior lobe and the posterior lobe. The anterior lobe regulates the activity of the thyroid, adrenals, and reproductive glands. The anterior lobe produces hormones such as:

    • growth hormone, which stimulates the growth of bone and other body tissues and plays a role in the body’s handling of nutrients and minerals
    • prolactin (pronounced: pro-LAK-tin), which activates milk production in women who are breastfeeding
    • thyrotropin (pronounced: thy-ruh-TRO-pin), which stimulates the thyroid gland to produce thyroid hormones
    • corticotropin (pronounced: kor-tih-ko-TRO-pin), which stimulates the adrenal gland to produce certain hormones

    The pituitary also secretes endorphins (pronounced: en-DOR-fins), chemicals that act on the nervous system and reduce feelings of pain. In addition, the pituitary secretes hormones that signal the reproductive organs to make sex hormones. The pituitary gland also controls ovulation and the menstrual cycle in women.

    The posterior lobe of the pituitary releases antidiuretic(pronounced: an-ty-dy-uh-REH-tik) hormone, which helps control the balance of water in the body. The posterior lobe also produces oxytocin (pronounced: ahk-see-TOE-sin), which triggers the contractions of the uterus in a woman having a baby.


    The thyroid (pronounced: THY-royd), located in the front part of the lower neck, is shaped like a bow tie or butterfly and produces the thyroid hormones thyroxine (pronounced: thy-RAHK-sin) andtriiodothyronine (pronounced: try-eye-oh-doe-THY-ruh-neen). These hormones control the rate at which cells burn fuels from food to produce energy.

    The production and release of thyroid hormones is controlled bythyrotropin (pronounced: thy-ruh-TRO-pin), which is secreted by the pituitary gland. The more thyroid hormone there is in a person’s bloodstream, the faster chemical reactions occur in the body.

    Why are thyroid hormones so important? There are several reasons — for example, they help kids’ and teens’ bones grow and develop, and they also play a role in the development of the brain and nervous system in kids.


    Attached to the thyroid are four tiny glands that function together called the parathyroids (pronounced: par-uh-THY-roydz). They release parathyroid hormone, which regulates the level of calcium in the blood with the help of calcitonin (pronounced: kal-suh-TOE-nin), which is produced in the thyroid.

    Adrenal Glands

    The body also has two triangular adrenal (pronounced: uh-DREE-nul) glands, one on top of each kidney.

    The adrenal glands have two parts, each of which produces a set of hormones and has a different function:

    1. The outer part, the adrenal cortex, produces hormones calledcorticosteroids (pronounced: kor-tih-ko-STER-oydz) that influence or regulate salt and water balance in the body, the body’s response to stress, metabolism, the immune system, and sexual development and function.
    2. The inner part, the adrenal medulla (pronounced: muh-DUH-luh), produces catecholamines (pronounced: kah-tuh-KO-luh-meenz), such as epinephrine (pronounced: eh-puh-NEH-frun). Also called adrenaline, epinephrine increases blood pressure and heart rate when the body experiences stress.


      The pineal (pronounced: pih-NEE-ul) body, also called the pineal gland, is located in the middle of the brain. It secretes melatonin(pronounced: meh-luh-TOE-nin), a hormone that may help regulate when you sleep at night and when you wake in the morning.

      Reproductive Glands

      The gonads are the main source of sex hormones. Most people don’t realize it, but both guys and girls have gonads.

      In guys the male gonads, or testes (pronounced: TES-teez), are located in the scrotum. They secrete hormones called androgens(pronounced: AN-druh-junz), the most important of which istestosterone (pronounced: tess-TOSS-tuh-rone). These hormones tell a guy’s body when it’s time to make the changes associated withpuberty, like penis and height growth, deepening voice, and growth in facial and pubic hair. Working with hormones from the pituitary gland, testosterone also tells a guy’s body when it’s time to produce sperm in the testes.

      A girl’s gonads, the ovaries (pronounced: OH-vuh-reez), are located in her pelvis. They produce eggs and secrete the female hormones estrogen (pronounced: ESS-truh-jen) and progesterone(pronounced: pro-JESS-tuh-rone). Estrogen is involved when a girl begins to go through puberty. During puberty, a girl will experience breast growth, will begin to accumulate body fat around the hips and thighs, and will have a growth spurt. Estrogen and progesterone are also involved in the regulation of a girl’s menstrual cycle. These hormones also play a role in pregnancy.

      Although the endocrine glands are the body’s main hormone producers, some other organs not in the endocrine system — such as the brain, heart, lungs, kidneys, liver, and skin — also produce and release hormones.


      The pancreas (pronounced: PAN-kree-us) is also part of the body’s hormone-secreting system, even though it is also associated with the digestive system because it produces and secretes digestive enzymes.

      The pancreas produces (in addition to others) two important hormones, insulin (pronounced: IN-suh-lin) and glucagon(pronounced: GLOO-kuh-gawn). They work together to maintain a steady level of glucose, or sugar, in the blood and to keep the body supplied with fuel to produce and maintain stores of energy.

      What Does the Endocrine System Do?

      Once a hormone is secreted, it travels from the endocrine gland that produced it through the bloodstream to the cells designed to receive its message. These cells are called target cells. Along the way to the target cells, special proteins bind to some of the hormones. These proteins act as carriers that control the amount of hormone that is available for the cells to use.

      The target cells have receptors that latch onto only specific hormones, and each hormone has its own receptor, so that each hormone will communicate only with specific target cells that have receptors for that hormone. When the hormone reaches its target cell, it locks onto the cell’s specific receptors and these hormone-receptor combinations transmit chemical instructions to the inner workings of the cell.

      When hormone levels reach a certain normal amount, the endocrine system helps the body to keep that level of hormone in the blood. For example, if the thyroid gland has secreted the right amount of thyroid hormones into the blood, the pituitary gland senses the normal levels of thyroid hormone in the bloodstream. Then the pituitary gland adjusts its release of thyrotropin, the hormone that stimulates the thyroid gland to produce thyroid hormones.

      Another example of this process is parathyroid hormone, which increases the level of calcium in the blood. When the blood calcium level rises, the parathyroid glands sense the change and reduce their secretion of parathyroid hormone. This turnoff process is called a negative feedback system.

      Things That Can Go Wrong

      Too much or too little of any hormone can be harmful to your body. For example, if the pituitary gland produces too much growth hormone, a teen may grow excessively tall. If it produces too little, a teen may be unusually short. Doctors can often treat problems with the endocrine system by controlling the production of hormones or replacing certain hormones with medication.

      Endocrine problems that can affect teens include:

      Adrenal insufficiency. This condition occurs when the adrenal glands don’t produce enough corticosteroids. The symptoms of adrenal insufficiency may include weakness, fatigue, abdominal pain, nausea, dehydration, and skin changes. Doctors treat adrenal insufficiency with medications to replace corticosteroid hormones.

      Type 1 diabetes. When the pancreas fails to produce enough insulin, type 1 diabetes (previously known as juvenile diabetes) occurs. In kids and teens, type 1 diabetes is usually an autoimmune disorder, which means that some parts of the body’s immune system attack and destroy the cells of the pancreas that produce insulin. To control their blood sugar levels and reduce the risk of developing diabetes problems, kids and teens with this condition need regular injections of insulin.

      Type 2 diabetes. Unlike type 1 diabetes, in which the body can’t produce normal amounts of insulin, in type 2 diabetes the body can’t respond to insulin normally. Kids and teens with the condition tend to be overweight. Some kids and teens can control their blood sugar level with dietary changes, exercise, and oral medications, but many will need to take insulin injections like people with type 1 diabetes.

      Growth hormone problems. Too much growth hormone in kids and teens who are still growing will make their bones and other body parts grow excessively. This rare condition (sometimes called gigantism) is usually caused by a pituitary tumor and can be treated by removing the tumor. The opposite can happen when a kid or teen has a pituitary glad that doesn’t produce enough growth hormone. Doctors may treat these growth problems with medication.

      Hyperthyroidism. Hyperthyroidism is a condition in which the levels of thyroid hormones in the blood are very high. In kids and teens, the condition is usually caused by Graves’ disease, an immune system problem that causes the thyroid gland to become very active. Doctors may treat hyperthyroidism with medications, surgery, or radiation treatments.

      Hypothyroidism. Hypothyroidism is a condition in which the levels of thyroid hormones in the blood are very low. Thyroid hormone deficiency slows body processes and may lead to fatigue, a slow heart rate, dry skin, weight gain, and constipation. Kids and teens with this condition may also grow more slowly and reach puberty at a later age. Hashimoto’s thyroiditis is an immune system problem that often causes problems with the thyroid and blocks the production of thyroid hormone. Doctors often treat this problem with medication.

      Precocious puberty. If the pituitary glands release hormones that stimulate the gonads to produce sex hormones too early, some kids may begin to go through puberty at a very young age. This condition is called precocious puberty. Kids and teens who are affected by precocious puberty can be treated with medication that will help them develop at a normal rate.


      Diabetes mellitus is the most common endocrine disorder and occurs when the pancreas either does not produce sufficient insulin or the body cannot use the available insulin. Symptoms of both type 1 and type 2 diabetes include:

      • Excessive thirst or hunger
      • Fatigue
      • Frequent urination
      • Nausea and vomiting
      • Unexplained weight loss or gain
      • Vision changes

      Common symptoms of acromegaly

      Acromegaly is a disorder in which the pituitary gland overproduces growth hormone. This leads to symptoms of overgrowth, especially of the hands and feet. Symptoms of acromegaly include:

      • Abnormally large lips, nose or tongue
      • Abnormally large or swollen hands or feet
      • Altered facial bone structure
      • Body and joint aches
      • Deep voice
      • Fatigue and weakness
      • Headaches
      • Overgrowth of bone and cartilage and thickening of the skin
      • Sexual dysfunction, including decreased libido
      • Sleep apnea
      • Vision impairment

      Common symptoms of Addison’s disease

      Addison’s disease is characterized by decreased production of cortisol and aldosterone due to adrenal gland damage. Common symptoms of Addison’s disease include:

      • Depression
      • Diarrhea
      • Fatigue
      • Headache
      • Hyperpigmentation of the skin (bronze appearance)
      • Hypoglycemia (low blood glucose)
      • Loss of appetite
      • Low blood pressure (hypotension)
      • Missed menstrual periods
      • Nausea, with or without vomiting
      • Salt cravings
      • Unexplained weight loss
      • Weakness (loss of strength)

      Common symptoms of Cushing’s syndrome

      Cushing’s syndrome arises from excess cortisol, produced by the adrenal glands. Symptoms of Cushing’s syndrome include:

      • Buffalo hump (fat between the shoulder blades)
      • Skin discoloration such as bruising
      • Fatigue
      • Feeling very thirsty
      • Thinning and weakening of the bones (osteoporosis)
      • Frequent urination
      • High blood sugar (hyperglycemia)
      • High blood pressure (hypertension)
      • Irritability and mood changes
      • Obesity of the upper body
      • Rounded “moon“ face
      • Weakness (loss of strength)

      Common symptoms of Graves’ disease

      Graves’ disease is a type of hyperthyroidism resulting in excessive thyroid hormone production. Common symptoms of Graves’ disease include:

      • Bulging eyes (Graves’ ophthalmopathy)
      • Diarrhea
      • Difficulty sleeping
      • Fatigue and weakness
      • Goiter (enlargement of the thyroid gland)
      • Heat intolerance
      • Irregular heart rate
      • Irritability and mood changes
      • Rapid heart rate (tachycardia)
      • Thick or red skin on the shins
      • Tremors
      • Unexplained weight loss

      Common symptoms of Hashimoto’s thyroiditis

      Hashimoto’s thyroiditis, or autoimmune thyroiditis, is a condition in which the thyroid is targeted by the immune system, leading to hypothyroidism and low production of thyroid hormone. Often, Hashimoto’s thyroiditis is symptomless, but symptoms can include:

      • Cold intolerance
      • Constipation
      • Dry hair and loss of hair
      • Fatigue
      • Goiter (enlargement of the thyroid gland)
      • Joint and muscle pain
      • Missed menstrual periods
      • Slowed heart rate
      • Weight gain

      Common symptoms of hyperthyroidism

      Hyperthyroidism is a condition characterized by an overactive thyroid gland. Common symptoms of hyperthyroidism include:

      • Diarrhea
      • Difficulty sleeping
      • Fatigue
      • Goiter (enlargement of the thyroid gland)
      • Heat intolerance
      • Irritability and mood changes
      • Rapid heart rate (tachycardia)
      • Tremors
      • Unexplained weight loss
      • Weakness (loss of strength)

      Common symptoms of hypothyroidism

      Hypothyroidism is a condition in which the thyroid is underactive and produces too little thyroid hormone. Often, hypothyroidism can be symptomless or very mild. Common symptoms of hypothyroidism include:

      • Cold intolerance
      • Constipation
      • Decreased sweat production
      • Dry hair
      • Fatigue
      • Goiter (enlargement of the thyroid gland)
      • Joint and muscle pain
      • Missed menstrual periods
      • Slowed heart rate
      • Swollen face
      • Unexplained weight gain

      Common symptoms of prolactinoma

      Prolactinoma arises when a dysfunctional pituitary gland makes excess prolactin hormone, which functions in the production of breast milk. Excess prolactin can lead to symptoms such as:

      • Erectile dysfunction
      • Infertility
      • Loss of libido
      • Missed menstrual periods
      • Unexplained milk production

      Serious symptoms that might indicate a life-threatening condition

      In some cases, endocrine disorders can be life threatening. Seek immediate medical care (call 911) if you, or someone you are with, have any of these serious symptoms that might indicate a life-threatening condition including:

      • Confusion or loss of consciousness for even a brief moment
      • Dangerously low blood pressure (extreme hypotension)
      • Dangerously slow heart rate
      • Dehydration
      • Depression or anxiety
      • Difficulty breathing
      • Eye problems, including dryness, irritation, pressure, pain or bulging
      • Severe fatigue or weakness
      • Severe, unexplained headache
      • Severe vomiting and diarrhea
      • Sleep disturbances

Causes of endocrine disorders

A number of factors are believed to cause endocrine disorders. Types and causes of endocrine disorders include:

  • Acromegaly, an overproduction of growth hormone, and prolactinoma, an overproduction of prolactin hormone, resulting from damage to the pituitary gland

  • Addison’s disease and Cushing’s syndrome, disorders relating to changes in levels of hormones produced by the adrenal glands

  • Diabetes mellitus, which arises when the pancreas does not produce sufficient insulin or when the body cannot respond to the insulin that is present

  • Environmental or nutritional factors, such as a lack of iodine in hypothyroidism, which can affect hormone production

  • Genetic factors, which may play a role in endocrine disorders, especially with diabetes and other disorders, such as autoimmune thyroiditis, or Hashimoto’s thyroiditis

  • Hyperthyroidism (overactive thyroid), hypothyroidism (underactive thyroid), Graves’ disease (a type of hyperthyroidism resulting in excessive thyroid hormone production), and Hashimoto’s thyroiditis (autoimmune disease resulting in hypothyroidism), all resulting from problems with the thyroid gland

  • Tumors, since the underlying cause of the endocrine disorder can be linked to a growth or tumor of the gland

In many cases, the exact cause of a particular endocrine disorder is not known. Often, hormones interact with each other, so symptoms of a particular endocrine disorder may be nonspecific. It is important to seek medical evaluation if you believe you may have an endocrine disorder, as direct assessment of hormone levels may help find and fix the underlying cause of hormone imbalance.

What are the risk factors for endocrine disorders?

A number of factors increase the risk of developing endocrine disorders. Not all people with risk factors will develop endocrine disorders. Risk factors for endocrine disorders include:

  • Elevated cholesterol levels

  • Family history of endocrine disorder

  • Inactivity

  • Personal history of autoimmune disorders, such as diabetes

  • Poor diet

  • Pregnancy (in cases such as hyperthyroidism)

  • Recent surgery, trauma, infection, or serious injury

Reducing your risk of endocrine disorders

While many endocrine disorders are inherited or arise for unknown reasons, some may be related to modifiable lifestyle factors. You may be able to lower your risk of certain endocrine disorders, such as hypothyroidism, by:

  • Eating a balanced, healthy diet

  • Living a healthy lifestyle, including regular physical activity


Medicines used to treat endocrine disorders

The leaflets in this section are authored by an experienced pharmacist. Pharmacists are experts in medicines. The medicines in this section include those which act on the endocrine glands. Endocrine glands release hormones (chemicals) into the blood and include the thyroid, pancreas, pituitary, ovaries and testes. Many of the medicines in this section are different types of treatment used in diabetes, but there are also medications for the thyroid (levothyroxine and carbimazole). They include insulin, metformin and gliclazide as well as the newer treatments like sitagliptin and liraglutide. If you’ve ever thought “Who shouldn’t take metformin?”, “How do I take my prednisolone?”, “How do I get the most from my insulin treatment?” or “What problems can bromocriptine cause?” information leaflets in this section will have answers for you.

Acarbose for diabetes (Glucobay)

Bromocriptine (Parlodel)

Cabergoline tablets (Dostinex, Cabaser)

Carbimazole tablets (Neo-Mercazole)

Co-cyprindiol tablets (Clairette, Dianette)

Cyproterone – an anti-androgen for men (Cyprostat, Androcur)

Danazol (Danol)

Dapagliflozin tablets (Forxiga)

Desmopressin (DDAVP, DesmoMelt, Desmospray, Desmotabs, Octim)


Diazoxide (Eudemine)

Dihydrotachysterol (AT 10)

Exenatide for diabetes (Byetta, Bydureon)

Fludrocortisone tablets (Florinef)

Glibenclamide for diabetes

Gliclazide (Diamicron, Dacadis, Nazdol, Zicron)

Glimepiride (Amaryl)

Glipizide (Minodiab)

Hydrocortisone tablets for cortisol replacement (Plenadren)


Levothyroxine (Eltroxin)

Linagliptin tablets

Liothyronine tablets

Liraglutide for diabetes (Victoza)

Lixisenatide for diabetes (Lyxumia)

Mesterolone tablets (Pro-Viron)

Metformin for diabetes

Metyrapone (Metopirone)

Nafarelin nasal spray (Synarel)

Nateglinide for diabetes (Starlix)

Pioglitazone tablets for diabetes (Actos, Diabiom, Glidipion)


Quinagolide tablets (Norprolac)

Repaglinide for diabetes (Enyglid, Prandin)

Saxagliptin for diabetes (Onglyza)

Sitagliptin for diabetes (Januvia)

Testosterone (Nebido, Restandol, Sustanon 250, Testim, Testogel, Tostran)


 How are endocrine disorders treated?

In many cases, endocrine disorders may be symptomless or mild enough to not require treatment. Symptoms can arise from excess hormone production or a hormone deficiency. When symptoms of endocrine disorders are bothersome, they can generally be treated by correcting the hormone imbalance. This is often done by means of synthetic hormone administration. In cases such as prolactinoma, where a noncancerous tumor is responsible for symptoms, surgery or radiation therapy may be used. Often, diagnosis and treatment of the underlying cause of the endocrine disorder will resolve the symptoms.

What are the potential complications of endocrine disorders?

While most endocrine disorders are mild and slow to progress, certain endocrine disorders can lead to complications over time as unbalanced hormonal signaling affects normal body processes. In cases of Addison’s disease and hypothyroidism in particular, acute attacks or crises can have serious complications. Diabetes can also have potentially life-threatening complications. Complications of untreated or poorly controlled endocrine disorders can be serious, even life threatening in some cases. You can help minimize your risk of serious complications by following the treatment plan you and your health care professional design specifically for you. Complications of certain endocrine disorders include:

  • Anxiety or insomnia (in many thyroid conditions)
  • Coma (in hypothyroidism)
  • Depression (in many thyroid conditions)
  • Heart disease
  • Nerve damage
  • Organ damage or failure
  • Poor quality of life;



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