Endocrine Exam

alike

• they both release ligands (chemical messengers) that bind to receptors on target cells

different

• the endocrine system:

  • transmits hormones through the blood

  • can target any cell in the body that has the right receptors

  • exhibits longer reaction times and has longer-lasting effects

How are the endocrine system and nervous system alike and different?

• regulating growth, development, and metabolism

• maintaining homeostasis of blood composition and volume

  • (hormones regulate blood solute concentration and volume)

• controlling digestive processes

  • (by influencing secretory processes and movement)

• controlling reproductive function and activities

What are the 4 general functions of the endocrine system?

pituitary, pineal, thyroid, parathyroid, and adrenal

What glands are true endocrine glands?

• hormonal stimulation

  • gland cells release hormone when some other hormone binds to it

• humoral stimulation

  • gland cells release hormone when there’s a certain change in levels of a nutrient or ion in the blood

• nervous system stimulation

  • gland cells release hormone when a neuron stimulates it

What are the 3 methods of stimulation that release hormones into the blood?

lipid-soluble hormones created by cholesterol

functions: growth, development, and reproduction

examples: testosterone, estrogen, cortisol

What are steroid hormones?

water-soluble, modified amino acids

examples: epinephrine, norepinephrine, thyroid hormone, and melatonin

What are biogenic amine hormones?

water-soluble chains of amino acids

consists of most hormones (antidiuretic hormone, insulin, glucagon, etc.)

What are protein hormones?

signaling molecules that DO NOT circulate in the blood

autocrine stimulation

• local hormone binds to the cells that release them

paracrine stimulation

• local hormone binds to neighboring cells

What are local hormones and the 2 types of local signaling they perform?

eicosanoids are local hormones formed from fatty acids

prostaglandins are eicosanoids that stimulate pain and inflammatory processes

What are eicosanoids and prostaglandins?

the time it takes to reduce a hormone’s concentration in the blood to half of its original value

• hormones that have a short half life must be secreted frequently into the blood

• steroid hormones have longer half lives

What is the half life of a hormone?

up-regulation is when the number of receptors on a target cell is increased (this creates increased sensitivity to hormones that bind)

down-regulation is when the number of receptors on a target cell is decreased (this creates decreased sensitivity to hormones that bind)

What is up-regulation and down-regulation?

target cells do this in response to hormone levels in the blood

low amount of hormone = up-regulate

high amount of hormone = down-regulate

Why might target cells up-regulate and down-regulate?

1. synergistic interaction

   1. one hormone reinforces the activity of another

   2. ex: estrogen & progesterone are more powerful together

2. permissive interaction

   1. one hormone requires the activity of another hormone to work

   2. ex: oxytocin (milk ejection) cannot work without prolactin (milk production)

3. antagonistic interaction

   1. one hormone opposes the activity of another

   2. ex: insulin lowers blood glucose and glucagon

What are the three types of interactions hormones can have on a target cell?

anatomy

• inferior to hypothalamus and is connected to hypothalamus by the infundibulum

• divided into anterior and posterior parts

functions

• master gland that produces, stores, and releases hormones

Describe the anatomy and functions of the pituitary gland

maintaining homeostasis by producing and releasing hormones for:

• regulating body temperature

• maintaining blood pressure

• reproduction

• appetite

Describe the function of the hypothalamus

IGF works synergistically with growth hormone to stimulate cell growth and division in bone and other tissue

it manages the effects of growth hormone

What are the effects of insulin-like growth factor (IGF)?

follicular cells

they also create thyroglobulin (the precursor for thyroid hormone)

What cells of the thyroid gland synthesize T3 and T4 hormones?

parafollicular cells

What cells in the thyroid gland synthesize calcitonin?

1. medulla

   1. inner part that releases epinephrine and norepinephrine

2. cortex

   1. synthesizes lots of corticosteroids

What are the two sections of the adrenal gland?

melatonin

it causes drowsiness and regulates the body’s circadian rhythm

What hormone is released by the pineal gland, and what is its function?

clusters of endocrine cells on the pancreas

alpha cells

• secretes glucagon

beta cells

• secretes insulin

What are pancreatic islets?

1. zona glomerulosa

2. zona fasciculata

3. zona reticularis

What are the three layers of the adrenal cortex, from superficial to deep?

the efficiency of the endocrine system decreases

additionally, some hormones decrease (ex: GH and sex hormones)

How does endocrine activity change as you age?

leptin

controls appetite and regulates energy expenditure

(low body fat = less leptin, which stimulates appetite)

What hormone does adipose CT produce?

D₃ enters the blood and is converted to calcidiol by liver enzymes

Calcidiol then arrives at the kidneys and becomes calcitriol (via kidney enzymes)

What happens to vitamin D₃ in the body?

releasing hormones (increases secretion of anterior pituitary hormones)

• thyrotropin-releasing hormone (TRH)

  • stimulates anterior pituitary to release TSH

• prolacin-releasing hormone (PRH)

  • stimulates anterior pituitary to release prolactin

• gonadotropin-releasing hormone (GnRH)

  • stimulates anterior pituitary to release FSH and LH (gonadotropins)

• corticotropin-releasing hormone (CRH)

  • stimulates the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary

• growth hormone-releasing hormone (GHRH)

  • stimulates anterior pituitary to release growth hormone (GH)

inhibiting hormones (decreases secretion of anterior pituitary hormones)

• prolactin-inhibiting hormone (PIH)

  • stops the release of prolactin

• growth-inhibiting hormone (GIH)

  • stops the release of GH

HAS A BIG ROLE IN INFLUENCING THE PITUITARY

What hormones are released by the hypothalamus, and what are their basic functions?

1. hormone diffuses across plasma membrane of cell

2. hormone binds to a receptor and creates a hormone-receptor complex

3. the complex binds to a specific segment of DNA called the hormone-response element

4. mRNA synthesis is stimulated

5. mRNA exits nucleus and binds to a ribosome and protein synthesis occurs

How do steroid hormones interact with target cells?

water soluble

• diffuses into the blood

lipid soluble

• requires a carrier protein to travel through the blood

What is the difference between how water soluble and lipid soluble hormones travel through the blood?

1. thyroid-stimulating hormone (TSH)

   1. trigger: thyroid release hormone from the hypothalamus

   2. function: causes the release of thyroid hormone from the thyroid

2. adrenocorticotropic hormone (ACTH)

   1. trigger: corticotropin-releasing hormone from the hypothalamus

   2. function: causes the release of corticosteroids from the adrenal cortex

3. follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

   1. trigger: GnRH release from the hypothalamus

   2. function: in women: regulates ovarian development and secretion of estrogen; in men: sperm development and secretion of testosterone

List 4 hormones the anterior pituitary gland releases, their trigger for release, and their functions

the hypothalamus hormonally stimulates the anterior pituitary to release hormones

the hypothalamus releases releasing/inhibiting hormones, which stimulates the anterior pituitary to release tropic hormones

How does the hypothalamus influence the anterior pituitary gland?

second messenger system

Protein hormones must use a ______ to interact with their target cells

1. enzymatic degradation (happens in liver cells)

2. removal via kidney excretion

3. target cell uptake

What are the 3 ways hormones can be eliminated from the blood?

the surgical removal of the pituitary gland due to tumors present

post-procedure: various hormones need to be replaced and their levels are consistently monitored

What is a hypophysectomy?

low growth hormone production

results in pituitary dwarfism (short stature and low blood sugar)

due to problems of the hypothalamus or pituitary gland

What is growth hormone deficiency?

the release of too much growth hormone

characterized by excessive growth, large internal organs, and increased blood sugar

What is pituitary gigantism?

disorder caused by excessive growth hormone production as an adult

effects: large bones of the face, hands, feet, and internal organs

also results in increased release of glucose

What is acromegaly?

excessive production of thyroid hormone

increased metabolic rate, weight loss, hyperactivity, and heat intolerance

can result from:

• T4 ingestion

• excessive stimulation by the pituitary gland

• loss of feedback control in the thyroid

What is hyperthyroidism?

the result of decreased thyroid hormone (TH) production

low metabolic rate, lethargy, cold intolerance, and weight gain

caused by:

• decreased iodine intake

• loss of pituitary stimulation by the thyroid

• postsurgical or immune system destruction of thyroid gland

What is hypothyroidism?

the enlargement of the thyroid

typically due to insufficient intake of iodine in the diet (this results in a lack of thyroid hormone production)

What is goiter?

the chronic exposure to excessive glucocorticoid hormones in people taking corticosteroids for therapy

can result in obesity, hypertension, hirsutism, kidney stones, and menstrual irregularities

What is cushing syndrome?

develops when the adrenal glands fail

chronic shortage of glucocorticoids and mineralocorticoids

weight loss, fatigue and weakness, hypotension, and skin darkening

What is Addison’s disease?

disorder that begins in the embryo or fetus

the inability to synthesize corticosteroids

leads to overproduction of adrenocorticotropic hormone (ACTH), high ACTH causes an increased size of the adrenal glands and production of hormones with testosterone-like effects

What is adrenogenital syndrome (congenital adrenal hyperplasia)?

• general umbrella term for diabetes

• it is the inadequate uptake of glucose from the blood

  • results in chronically elevated glucose in the blood

  • leads to blood vessel damage, blindness, kidney failure, and amputations

  • increased risk of heart disease and stroke

What is diabetes mellitus?

the diminished release of insulin by the pancreas

requires daily injections of insulin

What is type 1 diabetes?

condition caused by a decreased insulin release

obesity is a major cause

What is type 2 diabetes?

potential condition in pregnant women

if untreated, it can cause risk to the fetus and increases delivery complications

also increases the chances of developing type 2 diabetes later on

What is gestational diabetes?

when blood glucose levels are below 60 mg/dL

can be caused by:

• insulin overdose

• prolonged exercise

• alcohol use

• liver or kidney disfunction

• hormone deficiency

symptoms include hunger, dizziness, confusion, sweating, and sleepiness

What is hypoglycemia?

a chemical made by follicular cells in the thyroid gland

contains the amino acid tyrosine (important in TH synthesis)

What is thyroglobulin?

1. iodide (I^-) enters a follicular cell (via active transport) from the blood

2. iodide diffuses into the colloid

3. iodide converts to iodine and binds to thyroglobulin

4. thyroglobulin binds its tyrosine to the iodine, then the thyroglobulin detaches

5. tyrosine and iodine together are T₃ and T₄ (depending on the number of iodine atoms they have) and are released into the blood (via simple diffusion)

What are the 5 steps of thyroid hormone production?

• ADH

  • fluid retention and maintaining blood volume and pressure

• Oxytocin

  • stimulates contraction of uterus and breasts, emotional bonding

What two hormones are released from the posterior pituitary, and what are their functions?