Endocrine System

Endocrine system

all integrated system of small organs that release hormones, organs such as the heart, small intestine and stomach can also secrete hormones but are not part of this system since their primary purpose is not hormone secretion

Hormones

series of organs and glands that secrete chemical messengers (tell cells what to do ) into the bloodstream
Each is specific, recognized by corresponding target cells (>50)
Target cells have specific hormone receptors
Control growth, metabolism, sexual development and function
Regulated by feedback systems

Functions of the endocrine system

Homeostasis: Coordinates and integrates all bodily functions into one harmonious whole, setpoints throughout the body define homeostasis
Regulations of body functions:
Collects information and sends "orders" to the body, slower than the nervous system
Set points (standard or ideal levels)
Body can measure, store (remember), and correct for ideal set points
Effects may last for minutes, hours, or days
Responsible for growth, reproduction, and metabolism
Hormone production and secretion: each gland is responsible for synthesis and secretion of specific hormones

Negative feedback system

usually controls the stress response, begins with a drop in level of a hormone in the bloodstream
When a system in the body is under an abnormal condition, it triggers responses throughout the body in attempts to return it to a state of homeostasis
Once homeostasis is achieved the stimulus is removed
Ex. sweating and shivering until the body controls the temperature
During exercise, muscles contract and produce extra CO2 and trigger increased breathing to balance out CO2 with O2
Insulin to lower blood sugar, glucagon to raise blood sugar

Positive feedback system

Much less common, used only by the body in certain situations, increasing the magnitude of a change
Action continues until the stimulus is removed
During labor the uterus contracts and continues until the baby is delivered when contractions start oxytocin is released- triggers stronger and more frequent contractions
During the process of blood clotting. When a tissue is injured, signal chemicals are released. These chemicals activate circulating platelets to release more of these chemicals to activate more platelets that are essential during the formation of a blood clot.

Physiological response to stress

the cerebral cortex (corticol) centers in the brain sense a disturbing stimulus, activate pathways throughout the limbic system
Sympathetic: adrenal medullary axis and renin-angiotensin systems regulate cardiovascular system and metabolic functions (increase heart rate, breathing, release of glucose) to overcome stress
Later if stress persists hypotalamic-pituitary-adrenal axis (HPA),
helps to maintain the response (results in CRH-ACTH which releases glococorticoids)
Receptors through the body modulate the stress effects (cardiovascular, immune function, etc.)

Glands

there's two types of glands like endocrine and exocrine
Ex. hypothalamus, pituitary, pineal, thyroid, parathyroid, thymus, pancreas, adrenals, ovaries/testes

Endocrine glands

secrete substances into the bloodstream and travel into the body to reach their target organs, contains "ductless" glands

Exocrine glands

secrete substances that leave the body through a duct, ex. Sweat glands

Hypothalamus

"Master switchboard"
Control and relay center of the endocrine system
Regulates body temperature
Responsible for the release and inhibition of hormones
GHRH, GHIH, TRH, CRH, GnRH, PIF, PRH
Makes antidiuretic hormone (ADH) and oxytocin
Releasing hormones turn on the anterior pituitary
Inhibiting hormones turn off the anterior pituitary

Pituitary gland

The "Master Gland"
Connected to the hypothalamus by nerves and blood vessels
Controls all the other endocrine glands
Anterior and posterior pituitary

Anterior pituitary

produces and releases hormones \n TSH, FSH (follicle stimulating hormone), LH, GH, PRL, ACTH (adrenocorticotropic hormone)

Posterior pituitary

produces hormones through nerve cells in the hypothalamus and releases
ADH, Oxytocin

Pineal gland

Regulates sleep/wake patterns
Associated with biological clock
Melatonin hormone is secreted directly into the CSF and bloodstream and communicated with receptors sites in the brain

Thyroid gland

Butterfly shaped gland, with 2 lobes on each side of the trachea below the larynx
Releases T4 (thyroxine)- 95%
Releases T3 (triiodothyronine)- 5%, both need iodine
Affects speed of metabolism in all cells (helps grow and mature the body)
Controls how quickly the body uses energy, makes proteins, and controls how sensitive the body should be to other hormones
Calcitonin- reduces calcium in blood

Parathyroid gland

4 pea sized glands just behind the thyroid
Releases PTH (parathyroid hormone)
Increases reabsorption of calcium from the GI tract and the kidneys

Thymus

Located behind the sternum
Bi-lobed (in front of and above the heart)
Largest at birth, doubles in size by puberty and then gradually shrinks
Releases thymosin
Activates the immune system (T cells)

Adrenal glands

Located on top of each kidney about 5 cm long
Cortex-outer, Medulla-inner layer
Medulla releases adrenalin/nonadrenalin
Cortex releases glucocorticoids, gonado-corticoids, mineral-corticoids
Help regulate metabolism, immune system, blood pressure, response to stress
Helps burn protein and fat, produces hormones that control blood sugar

Pancreas

Located behind the stomach, several million islets of
Langerhans
the largest endocrine gland
2 opposing hormones
Insulin: binds with glucose and takes into cells decreasing amount of glucose in blood stream ("blood sugar")
Glucagon: converts glycogen stored in the liver to glucose to increase the amount of glucose in the bloodstream

Gonads/Testes

Primary reproductive organs, testes in the male and ovaries in the female
These organs are responsible for producing sperm and ova
Progesterone, testosterone, estrogen

TSH

Thyroid stimulating hormone
The pituitary stimulates the thyroid to produce T3 and T4 which stimulates the metabolism of almost every tissue in the body, released into bloodstream
If you have too much, it will lead to hyperthyroidism (overactive thyroid) \n If you have less, it will lead to hypothyroidism (underactive thyroid)

LH

Made by the pituitary gland, luteinizing hormone
In women, it helps control the menstrual cycle, It triggers the release of an egg from the ovary
In men, it causes the testicles to make testosterone, which is important for producing sperm
Goes to the testes and ovaries
Too much or too little can cause a variety of problems, including infertility, menstrual difficulties in women, low sex drive, and early or delayed puberty in children

Oxytocin

A natural hormone produced by the hypothalamus and the pituitary stimulates uterine contractions in childbirth and lactation after childbirth. It also affects aspects of human behavior and the male and female reproductive systems
Goes to the blood, brain or spinal cord
High levels result in oversensitivity to the emotions of others
Low levels can result in hormone dysregulation (with sex hormones), stop uterine contractions during birth, difficulty breast feeding

ADH

Antidiuretic hormone produced by the hypothalamus and secreted by pituitary, helps blood vessels constrict (blood pressure) and helps the kidneys control the amount of water and salt in the body
High levels lead to Syndrome of inappropriate antidiuretic hormone secretion (SIADH), it causes the body to keep too much water and your blood and urine volume decreases
Low levels will cause the kidneys to excrete too much water. Urine volume will increase leading to dehydration and a fall in blood pressure

PRL

Prolactin is a hormone produced by the pituitary gland, a small gland at the base of the brain. It causes the breasts to grow and make milk during pregnancy and after birth
Released into the bloodstream
High levels means there is a type of tumor of the pituitary gland, known as a prolactinoma, which makes excessive breast milk
Low levels can lead to insufficient milk being produced after giving birth

Melatonin

a hormone that your brain produces in response to darkness, sleep
It is produced in the pineal gland, then is released into the bloodstream or cerebrospinal fluid
High levels include excessive sleepiness, vomiting and trouble breathing
Low levels are also observed in various diseases, such as types of dementia, some mood disorders, severe pain, cancer, and diabetes type 2.

Cortisol

the primary stress hormone, your hypothalamus releases corticotropin-releasing hormone (CRH), which directs your pituitary gland to produce adrenocorticotropic hormone (ACTH), ACTH then stimulates your adrenal glands to produce and release cortisol into the bloodstream
most useful in handling stress, also heart function, blood pressure, inflammatory response, insulin use and glucose for energy
High levels can cause Cushing's syndrome
Low levels can cause Addison's disease

Epinephrine

Also known as adrenaline, the hormone and neurotransmitter plays an important role in your body's fight-or-flight response
Produced and secreted by adrenal medulla
High levels means high blood pressure, rapid or irregular heartbeat, excessive sweating, cold or pale skin.
Low levels mean anxiety, depression, changes in blood pressure, changes in heart rate

GH

Growth hormone, it stimulates the growth of essentially all tissues of the body, including bone
Produced in pituitary gland then released into bloodstream
High levels lead to gigantism
Low levels lead to dwarfism

Type 1 Diabetes

an organ specific autoimmune diseases caused by autoimmune response against pancreatic B cells. The body's immune system mistakenly targets cells in the pancreas that destroy its ability to make insulin, the hormone that helps the body control sugar levels. Usually treated with insulin injections or insulin pump

Type 2 Diabetes

Results when the pancreas produces insulin, but not enough, or the body becomes resistant. It's mainly lifestyle related and develops over time. It can be managed with weight, diet, oral medications, and sometimes insulin
If one is diagnosed, the cells do not respond to the insulin normally and this is known as insulin resistance
The pancreas tries to make more insulin to get the cells to respond but eventually the pancreas can't keep up and the blood sugar starts to rise.

Hyperglycemia

Too much sugar in the blood
Frequent urination
Increased thirst
Blurred vision
Feeling weak or unusually tired

Hypoglycemia

Not enough glucose for body needs
Fast heartbeat
Shaking
Sweating
Nervousness or anxiety
Irritability or confusion
Dizziness
Hunger

Gigantism

Too much growth hormone, excessive height/ deformity of body tissues
caused by an adenoma, or a tumor of the pituitary gland.
The pituitary tumor cells secrete too much growth hormones, leading to changes in the body
Symptoms: Delay in puberty, Abnormal enlargement of Hands or feet, Changes in facial features, Spreading teeth, Arthritis, Headaches, High blood pressure, Heart disease

Dwarfism

too little growth hormone
Failure to reach normal height (4'10") disproportionate or proportionate
Most commonly caused by a genetic mutation in an egg/sperm cell, this happens before conception. Less commonly, dwarfism is caused by an inherited gene from either parent
Symptoms: Smaller arms and legs compared to torso size, Short fingers, Limited mobility at the elbows, A disproportionately large head (with a prominent forehead and a flattened bridge of the nose), Dental Issues, Delayed Puberty

Cushing's disease

the pituitary gland overproduces the hormone ACTH (adrenocorticotropic hormone) which in turn causes the adrenal glands to produce too much cortisol
Caused by the development of tumors around the pituitary gland or adrenal gland, long-term use of corticosteroids, and chronic stress
Symptoms: abdominal obesity, high blood pressure, bad cholesterol, muscle weakness, easy bruising, hyperglycemia, severe fatigue, headaches

Addison's disease

adrenal insufficiency occurs when the immune system mistakenly attacks the adrenal cortex of the adrenal glands causing them to not produce enough cortisol and aldosterone
Symptoms: Weight loss, muscle weakness, fatigue, low blood pressure, darkening of skin

Grave's disease

Disorder resulting from hyperthyroidism
Hyperthyroidism is the overproduction of thyroid hormones
Caused by Higher vitamin D levels
It is an autoimmune disease
Symptoms: exophthalmos (bulging eyes), heat intolerance, and anxiety

Hashimoto's disease

When the body's immune system (anti-thyroid antibodies) attack the thyroid causing a leak resulting in limited thyroid hormones being released
Hypothyroidism is a small amount of thyroid hormones being produced
Symptoms: Fatigue, Weight gain, Trouble tolerating cold, Joint and muscle pain, Constipation, Dry skin, Dry thinning hair, Heavy or irregular menstrual periods, Fertility problems, Slowed heart rate, Brittle nails

Long term effects of elevated blood sugar

Damage to the blood vessels
High blood pressure
Increased risk of stroke
Damage to kidneys- renal failure
Diabetic retinopathy
Neuropathy