Endocrine Packet 1

The endocrine system is a network of glands in the body that make the hormones that help cells talk to each other.

  • Glands are organs that secrete chemical substances.

  • Endocrine glands release hormones into the bloodstream.

  • Hormones are chemical messengers that travel through the bloodstream to a target organ.

Some hormones target only one organ. Some hormones effect all over the body.

Endocrine System Functions

Produces hormones that control

  • Mood, growth, development, metabolism, organs, and reproduction

Many glands work based on negative feedback loop:

  • Gland A detects a low level of Hormone B

  • Gland A releases hormone A

  • Hormone A tells Gland B to make Hormone B

  • Once levels of Hormone B are back to normal, Gland A stops producing Hormone A

Hormone Chart

Pineal gland —> melatonin —> targets brain —> located in brain

Pituitary gland —> FSH, LH, ACTH, growth hormone, TSH, prolactin, oxytocin, ADH —> targets gonads, adrenals, thyroid, mammary, kidneys, bones —> located in brain

Thyroid —> T3, T4 —> targets everything —> located in neck

Adrenal gland —> cortisol, aldosterone, androgens, adrenaline —> targets kidneys, body cells, gonads, nervous system —> located above kidneys

Pancreas —> insulin, glucagon —> targets body cells, liver —> located in abdomen

Ovaries —> estrogen —> targets everything —> located in pelvis

Testes —> testosterone —> targets everything —> located in pelvis

Too much or too little chart

Growth hormone —> too much: acromegaly

Cortisol —> too much: Cushing’s syndrome —> too little: adrenal insufficiency

Estrogen —> too much: precocious puberty —> too little: premature ovarian failure, amenorrhea

Testosterone (in women) —> too much: PMOS

Thyroid hormone —> too much: hyperthyroidism —> too little: hypothyroidism

Parathyroid hormone —> too much: osteoporosis

Components of Endocrine System

Many glands make up the endocrine system

  • The hypothalamus, pituitary gland, and pineal gland are in the brain.

  • The thyroid and parathyroid glands are in the neck.

  • The thymus is between the lungs.

  • The adrenals are on top of the kidneys.

  • The pancreas is behind the stomach.

  • The ovaries or testes are in the pelvic region.

Hypothalamus

  • This organ connects the endocrine system with the nervous system.

  • It’s main job is to tell the pituitary gland to start or stop making hormones.

Pituitary gland

  • This is the endocrine system’s master gland.

  • It uses information it gets from the brain to tell other glands in the body what to do.

  • It is divided into the anterior and posterior lobe.

  • It makes many hormones that travel to different organs.

Anterior Pituitary Gland Hormones

  • Follicle Stimulating Hormone (FSH) —> promotes development of ova and sperm

  • Luteinizing Hormone (LH) —> manages estrogen in women and testosterone in men.

  • Adrenocorticotropic Hormone (ACTH) —> stimulates the adrenal gland to make certain hormones.

  • Thyroid Stimulating Hormone (TSH) —> stimulates the production and secretion of thyroid hormones

  • Prolactin —> helps with breastfeeding mothers milk production

  • Growth Hormone —> stimulates cell division in bones, cartilage

Posterior Pituitary Gland Hormones

  • Oxytocin —> helps in milk ejection during breastfeeding.

  • Antidiuretic Hormone (ADH or vasopressin) —> controls blood pressure and helps control body water balance through its effect on the kidneys.

Pineal Gland

  • It makes a chemical called melatonin that helps the body get ready to go to sleep.

Thyroid gland

  • This gland makes thyroid hormone (T3, T4), which controls growth and metabolism

  • Hypothyroidism: if this gland doesn’t make enough, everything happens more slowly.

  • Symptoms: slow heart rate, constipation, weight gain

  • Hyperthyroidism: if it makes too much everything speeds up.

  • Symptoms: fast heart rate, diarrhea, weight loss

  • The thyroid gland also produces the hormone calcitonin, which contributes to bone strength by helping calcium get incorporated into bone.

  • Calcitonin production is regulated by the C-cells of the thyroid.

Parathyroid Gland

  • This is a set of four small glands behind the thyroid that produce parathyroid hormone (PTH).

  • They play a role in bone health.

  • The glands control levels of calcium and phosphorus.

  • The parathyroid glands are named due to their location and are not involved with the thyroid gland or thyroid hormone.

Thymus

  • This gland makes white blood cells called T lymphocytes that fight infection and are crucial as a child’s immune system develops.

  • It atrophies over time and is much smaller by adulthood.

Adrenal Glands

  • The adrenal gland is divided into two sections: the adrenal medulla and the adrenal cortex.

  • The adrenal medulla is best known for making the “fight or flight” hormone adrenaline (also called epinephrine).

  • The adrenal cortex produces hormones that regulate electrolytes, blood sugar, and sexual function.

  • An easy way to remember the functions of the adrenal cortex: salt, sugar, sex

Pancreas

  • This organ is part of the digestive and endocrine systems.

  • The pancreas is an endocrine gland and an exocrine gland since it produces compounds that travel throughout the body (hormones) and very close to the organ itself (enzymes).

  • For the endocrine system, the pancreas produces the hormones insulin and glucagon.

  • These ensure you have the right amount of glucose in the bloodstream and cells.

Ovaries

  • In women, these organs make estrogen and progesterone.

  • These hormones help develop breasts at puberty, regulate the menstrual cycle, and support a pregnancy.

Testes

  • In men, the testes make testosterone.

  • It helps them grow facial and body hair at puberty.

  • It triggers penis growth at puberty.

  • It also plays a role in sperm production.

Endocrine Disorders

If your endocrine system isn’t healthy you might have a problem with:

  • Development during puberty

  • Becoming pregnant

  • Managing stress

  • Gain weight

  • Weak bones

  • Lack of energy

Acromegaly

  • Sometimes the pituitary gland makes too much growth hormone an bones get bigger.

  • It usually affects the hands, feet, and face.

  • It usually starts in middle age.

Adrenal insufficiency

  • Adrenal insufficiency is the term for when the body makes too little cortisol, which is the hormone produced in response to stress.

  • Addison’s disease is an auto-immune condition that destroys the adrenal gland’s production of certain hormones and a common cause of adrenal insufficiency.

  • If untreated, patient may develop adrenal crisis due to their electrolyte imbalance.

Amenorrhea

  • This menstrual condition happens when a female has no periods for more than three monthly menstrual cycles.

  • Almost always, amenorrhea is associated with low levels of estrogen.

  • Natural causes —> menopause and pregnancy

  • Abnormal causes —> excessive exercise, low body fat, PMOS, surgery, certain thyroid disorders

Cushing’s Syndrome

  • This condition is due to too much cortisol. This can be due to a patient taking a prescribed steroid or the body producing too much when it doesn’t need to.

  • A patient could gain weight, get stretch marks, bruise easily at first, then get weakened muscles and bones, and possibly develop a hump on their upper back

Hyperthyroidism

  • This is when your thyroid gland makes too much thyroid hormone. It is also called overactive thyroid.

  • Hyperthyroidism causes the body and organs to work harder and faster: a patient might feel nervous, lose weight, and have a rapid heartbeat or trouble sleeping.

Hypogonadism

  • This is when the testes or ovaries produce little to no amount of sex hormones.

  • In men, this causes low testosterone.

  • In women, this causes low estrogen and/or progesterone.

Hypothyroidism

  • When the body doesn’t make enough thyroid hormone, your body and organs slow down. This is also known as under active thyroid.

  • A patient might feel tired, gain weight, have a slow heartbeat, and get joint and muscle pains.

Hypopituitarism

  • Sometimes the pituitary gland doesn’t make enough of certain hormones

  • Tumors or damage to the pituitary gland are the most common causes.

  • This causes the glands controlled by the pituitary, like the adrenal and thyroid glands, to not receive messages to do their job.

Multiple Endocrine Neoplasia (MEN) are a problem

  • These are genetic disorders that can cause tumors in two or more endocrine glands.

  • MEN syndromes can be inherited from parents or arise sporadically.

  • Tumors produce increased amounts of hormone based on the organ they involve.

Osteoporosis

  • This is an endocrine disorder where hormones needed for healthy bone growth are compromised. A decline in estrogen and testosterone can lead to osteoporosis.

  • It happens when the body’s creation of new bone doesn’t keep up with the loss of old bone.

  • Sometimes, overproduction of parathyroid hormone can cause osteoporosis.

  • Over time, bone density declines and can lead to fragility fractures in the spine or hip.

Polyendocrine Metabolic Ovarian Syndrome (PMOS)

  • An imbalance of reproductive hormones can cause the ovaries to either not make an egg or not release it during ovulation.

  • PMOS is characterized by high androgen levels (testosterone) in women.

  • This can throw off periods, cause acne, and make hair grow on the face or chin.

Precocious Puberty

  • This condition is when kids start puberty early, younger than 8 for girls and younger than 9 for boys.

  • Often, no cause is identified.

  • When a cause is found it can be due to inappropriate production of GnRH from the hypothalamus.

  • In girls, an ovarian cyst can cause elevated estrogen.

  • In boys, a testicular tumor can cause elevated testosterone.

Premature Ovarian Failure

  • This occurs when estrogen declines before age 40 due to reduced production from the ovaries.

  • It can be due to genetic disorders, or medical procedures like ovarian surgery or chemotherapy.

  • A decline in estrogen production after age 40 is considered normal and part of menopause.

Other Modulators of the Endocrine System

  • Outside factors can change how the endocrine system functions: stress, infections, and exposure to certain chemicals can impact a person’s endocrine system.

  • Genes or lifestyle habits can increase the chances of an endocrine disorder like hypothyroidism, diabetes, or osteoporosis.