Endocrine System

What are hormones?

They are chemical messengers

Travel throughout the body

Coordinate activity between cells, tissues, and organs

Ways to secrete hormones

Endocrine

Paracrine

Autcrine

Endocrine

Hormones secrete hormones directly into the bloodstream

Paracrine

Hormones secrete into neighboring cells

Autocrine

Hormones secrete into the same cell that is secreting it.

Three main hormone types

1. Peptide hormones

2. Steroid Hormones

3. Amino Acid Derived hormones

Peptide Hormones

• What are they made of

• How do we make them?

Hormones based on proteins

• Synthesis: They are produced in the rough endoplasmic reticulum by linking amino acids through peptide bonds.

What do peptide hormones do? How do they act?

Bind to cell surface receptors rather than freely passing through cellular membranes

• Proteins are water soluble, not lipid soluble

Indirect Stimulation

Peptide hormone interaction with cell surface receptors kicks of a signal transduction pathway in order to carry out the signaling

Ligand gated receptors

Receptor proteins that are capable of inducing intracellular signal transduction pathways once an extracellular ligand is bound

Second Messengers

• Plus all 4 examples of them

Signaling molecules independent of the original hormone which propagate signals within the cell (intracellular effect)

• cAMP (cyclic AMP),

• IP3 (inositol triphosphate)

• DAG (diacylglycerol),

• Ca2+ (calcium ions)

GCPRs

GPCRs (G Protein Coupled Receptors): Associated with a G Protein on the intracellular domain that is responsible for conveying intracellular signals

• Ex Pathway: IP3/DAG

Receptor Tyrosine Kinases

• Receptor Tyrosine Kinases (RTKs) Twin components dimerize to and cross phosphorylate in order to influence intracellular signals

Ligand Gated Ion channels

• Ligand-Gated Ion Channels: Channel proteins which change shape once a ligand is bound in order to allow the flow of ions across membranes

IP3/DAG Pathway Purpose

Regulates the release of stored Ca2+ from the endoplasmic reticulum into the cell cytosol

IP3/ DAG Pathway

1. The pathway is activated when an appropriate peptide hormone binds the GPCR

2. GPCR activates the associated G protein via the binding of one GTP molecule

3. G protein activates the enzyme Phospholipase C

4. Activated Phospholipase C cleaves the lipid PIP2 into two separate second messengers (IP3 and DAG)

5. IP3 binds ligand gated Ca2 channels on the surface of the ER

6. ER calcium channels open, releasing Ca2+ into the cytosol

7. Free Ca2+ goes on to affect multiple other pathways

G Proteins —> goes from GDP to GTP to get activated.

Receptor Tyrosine Kinases

Peptide hormone receptor with an independent mechanism from the GPCR

• Made of two mirror components that dimerize once a peptide hormone is bound

• Intracellular RTK domains cross-phosphorylate to kick of a second messenger response

  • RTK components phosphorylate each other and affect other proteins

Steroid Hormones

• What are they made of

Hormones made from modified cholesterol molecules

Synthesis: Production occurs in the smooth endoplasmic reticulum

Structure: Basic fused 4-ring structures with differentiating functional groups

Where are steroid hormones made?

Synthesis: Production occurs Smooth Endoplasmic Reticulum. (same as fats, remember that)

Structure of steroid hormones

Basic fused 4-ring structures with differentiating functional groups

Where are hormones produced by the Adrenal Cortex and gonads stored?

They are stored as steroids.

Adrenal Cortex:

• Glucocorticoids

• Mineralocorticoids

• Androgenic Steroids

Reproductive Organs

• Progesterone

• Testosterone

• Estrogen

What do steroid Hormones do?

• How do they move around

• How do they activate things?

They are lipophillic hormones and can pass directly through a cellular membrane.

• Lipid Soluble NOT water soluble.

• Require association with water soluble transport protein to travel through the blood.

• Directly bind intracellular receptors of the cytoplasm or the nucleus

  • Results in steroid receptor complexes that directly bind to NDA to affect transcription

What is direct stimulation in hormones, and what type undergoes it?

Steroid Hormones undergo slow and gradual genetic change.

Amino Acid Derived Hormone Properties

• How are they made

• What are some example hormones.

Can have properties that are similar to both peptide and steroid hormones.

Synthesis: Produced in rough endoplasmic reticulum, and the cytosol and mainly derived from the amino acid tyrosine.

All hormones of the adrenal medulla as well as T3 and T4 hormones.

Adrenal Medulla Hormones

• Norepinephrine

• Epinephrine

Hypothalamus

• Purpose

The main thing respinsible for hormone secretion in the body.

• Coordinates the body’s internal environment and maintains homeostasis.

Pituitary Gland

a.k.a (hypophysis)

Crucial gland for hormone production, storage, and release

• Rests just below the hypothalamus

• Anterior pituitary and posterior pituitary

Posterior Pituitary gland

Posterior Pituitary (Neurohypophysis): The direct neuronal extension of the hypothalamus constructed of neuronal tissue

• Stores and releases hormones produced by the hypothalamus

Posterior Pituitary Gland Hormones (ADH)

Antidiuretic Hormone (ADH) aka. Vasopressin: Increases water reabsorption in the nephron by increasing the number of aquaporins in the collecting duct

• Reabsorption of water into the blood

• Antidiuretic (decrease in urination)

Posterior Pituitary Gland Hormones (Oxytocin)

Causes uterine contraction during child labor and the release of milk during breastfeeding

• Targets the uterus and mammary glands

• Operates in a positive feedback loop

• Plays a role in facilitating “maternal behavior”

Anterior Pituitary Gland

Anterior Pituitary (Adenohypophysis):

• Produces it own hormones and is composed of glandular tissue rather than neural tissue

Hypothalamic Releasing Hormones

Hormones released by the hypothalamus in order to stimulate the release of hormones generated by the anterior pituitary gland

Hypothalamic Inhibiting Hormones

Hormones released by the hypothalamus to inhibit the release of other hormones by the anterior pituitary

Hypophyseal Portal System,

Hypophyseal Portal System:

• Connects the anterior pituitary gland to the hypothalamus and allows for quick diffusion of hormones through a portal vein

Connects hypothalamus and the anterior pituitary.

Anterior Pituitary Gland Stimulating Hormones (4)

GnRH

TRH

CRH

GRH

GnRH

(Gonadotropin Releasing Hormone):

• Causes the release of luteinizing hormone (LH) and follicle stimulating hormone (FSH)

TRH

TRH (Thyrotropin Releasing Hormone):

• Causes the release of thyroid stimulating hormone (TSH)

CRH

(Corticotropin Releasing Hormone):

• Causes the release of adrenocorticotropic hormone (ACTH)

GRH

(Growth Hormone Releasing Hormone):

• Causes the release of growth hormone (GH)

Anterior Pituitary Gland Hormones

Once stimulated, the anterior pituitary can release its own hormones

Tropic and Direct Hormones

Tropic Hormones

Target other endocrine glands for further hormone release

• ACTH

• TSH

• LH

• FSH

Direct Hormones

Directly Targets organs to cause effects

TROPIC

FSH

• Purpose

Follicle growth in females and sperm maturation in male gonads

(follicle stimulating hormone)

TROPIC

LH

Lutenizing Hormone

• Stimulates ovulation, the formation of the corpus luteum in females (keep in mind this eventually produces estrogen), and the production of testosterone in male gonads

TROPIC

ACTH

(Adrenocorticotropic Hormone):

• Stimulates the release of glucocorticoids from the adrenal gland to fight stress

  • Increases the body’s glucose levels

TROPIC

TSH

TSH (Thyroid Stimulating Hormone): Stimulates the thyroid gland to produce T3 and T4 in order to increase metabolism

• LIPOPHILLIC

TROPIC

Direct Hormones of the Anterior Pituitary

• Prolactin

• Growth Hormone (somatotropin)

Prolactin

Stimulates the development of the mammary gland and increases milk production following childbirth

After childbirth, prolactin also increases milk production by stimulating lactation in the female.

Growth Hormone

Stimulates the growth and division of body cells

Anterior Pituitary Gland Hormones (pneumonic)

(tropic)

F Follicle Stimulating Hormone (FSH)

L. Luteinizing Hormone (LH)

A. Adrenocorticotropic Hormone (ACTH)

T. Thyroid Stimulating Hormone (TH)

(direct)

P. Prolactin

i.

G. Growth Hormone (Somatotropin)

Pineal Gland

Gland in the brain responsible for the production of melatonin

• Hormone involved in regulating the circadian rhythm

Thyroid Gland

The largest of the endocrine organs.

• In front of the trachea.

Parathyroid Gland

Endocrine glands on the posterior side of the thyroid gland.

Thyroid Gland Hormones

T3: triiodothyronine

T4: thyroxine

Calcitonin

T3 and T4

Triiodothyronine (T3) and Thyroxine (T4): Responsible for increasing metabolism in the body

• Released in response to TSH stimulation from the anterior pituitary

• Derived from the amino acid tyrosine

• Negative feedback effect on TSH (thyroid stimulating) and TRH (thyroid releasing hormone) secretion

LIPOPHILLIC

T3

T3: Active form of the hormone set

• 4x more potent than T4

LIPOPHILLIC

T4

Stable form of the hormone due to additional iodine atom

• Main circulating form of the hormone in blood

Lipophillic

Calcitonin

Released by parafollicular thyroid cells (c cells)

• Stimulates osteoblast use of calcium to generate new bone.

• Inhibits osteoclasts from freeing calcium by breaking down bone.

• Decreases Calcium Reabsorption in kidneys and intestines.

Hypothyroidism

Under secretion of T3 and T4, which causes reduced basal metabolic rates

Hyperthyroidism

Over secretion of T3 and T4, which causes increased basal metabolic rates.

Goiter in Hypothyroidism

The irregular, physical enlargement of the thyroid gland

1. Hypothyroidism = low T3 & T4 = over secretion of TRH (thyroid releasing hormone) to compensate for missing T3 & T4 = enlarged thyroid gland

Goiters: Hyperthyroidsism.

1. Hyperthyroidism = high T3 & T4 = hyperactive thyroid gland = enlarged thyroid gland

What is the main cause of goiters?

Iodine Deficiency

Parathyroid Gland:

Parathyroid Hormone: Increases blood calcium levels in the blood

Opposite of Calcitonin

• Stimulates osteoclasts to free calcium by breaking down bone

• Inhibits osteoblast use of calcium to generate new bone

• Increases calcium reabsorption in the kidneys and intestines

Calcitonin vs PTH

Pancreas purpose

An endocrine gland consisting of endocrine and exocrine tissues

Endocrine cells

Secrete hormones into the blood stream

Exocrine

Secrete hormones into ducts

What do the islets of langerhans secrete?

• What are they to an organ?

Endocrine (Islets of Langerhans): Secretion of the peptide hormones glucagon, insulin, and somatostatin

• Glucagon is released by Alpha (α) cells

• Insulin is released by Beta (β) cells

• Somatostatin is released by Delta (δ) cells

What do Alpha cells release (pancreas)

Glucagon

What do beta cells release? (pancreas)

Insulin

What do delta cells release?

Somatostatin INHIBITS

• This inhibits the growth hormone from the anterior pituitary

• glucagon from alpha cells

• Insulin from beta cells

Pancreatic Exocrine Functions

Exocrine: Secretion of digestive enzymes into the small intestine via the pancreatic duct

Glucagon

Released by alpha cells in times of low blood glucose.

• Stimulates Liver and adipose (fat) tissues to release their stored glucose

Insulin

Released by beta cells in times of high blood glucose

• Stimulates the liver, adipose (fat) and muscle tissues to store glucose.

Insulin and Glucose Transport

Insulin is a peptide hormone that associates

with a receptor tyrosine kinase (RTK)

• Resulting second messengers trigger the increase of glucose transporters along the cellular membrane

Glucose flows out of the blood and into cells, decreasing blood glucose levels

Somatostatin

Somatostatin from the pancreatic delta cells is an inhibitory hormone

Somatostatin is responsible for inhibiting the release of:

Insulin from the beta cells

Glucagon from the alpha cells

Growth hormone from the anterior pituitary

Adrenal Gland Anatomy

Our bodies house two distinct adrenal glands, each associated with the superior surface of one of our body’s kidneys

Adrenal Medulla

Adrenal Cortex

Adrenal Cortex → Location

Adrenal Cortex: Outer region of the adrenal gland

Adrenal Medulla: → location, and main function

Adrenal Medulla: region of the adrenal gland

• Overall adrenal gland function is associated with stress combatting

Adrenal Cortex

• Purpose

• What does it release

Glucocorticoids (Cortisol)

Mineralocorticoids

Androgens:

Deals with long term stress

Releases steroid hormones upon stimulation by Adrenocorticotropic hormone (ACTH) from the anterior pituitary gland.

Glucocorticoids

Glucocorticoids (Cortisol): Raise blood glucose levels for fuel use during long periods of stress; lowers immune response

• Released by the adrenal cortex

Mineralocrticoids

Mineralocorticoids (Aldosterone): Increases blood volume and blood pressure by increasing reabsorption of Na+; passive reabsorption of water via osmosis

• Released by the adrenal cortex

Androgens

Androgens: Male sex hormones produced in small amounts by the adrenal cortex

• Released by the adrenal cortex

Adrenal Medulla

Responsible for dealing with short term stress

• Releases amino acid derived hormones in response to stimulation by the sympathetic nervous system

Adrenal Medulla

• Releases amino acid derived hormones in response to stimulation by the sympathetic nervous system

Releases:

• Catecholamines

  • Epinephrine and Norepinephrine

Calecholamine

• Epinephrine and Norepinephrine

  • Fight or flight hormones that increase heart rate and breaks down glycogen into glucose

Epinephrine

Epinephrine: Binds alpha and beta adrenergic receptors to cause vasoconstriction and vasodilation

• Vasoconstriction occurs with alpha receptors

• Vasodilation occurs with beta receptors

Long term stress

• What manages it

• examples

Long Term

Dealt with by the adrenal cortex

● Examples might include: prolonged, insufficient access to food and water

Short term stress

• What manages it

• examples

Adrenal Medulla

● Examples might include: a sudden, frightening event or a perceived immediate threat to health and safety

Long term vs short term stress

• molecules

• Which one is faster?

Long term stresses are met with steroid hormones while short term stresses are met with amino acid derived hormones

• Amino acids must use signal transduction pathways, transmitting signals faster

Stimulation of the testes and ovaries.

• What are they stimulated by?

• Where are those stimulations send from

The anterior pituitary gland produces its own hormones, which can be either tropic or direct

• Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH) are both tropic hormones and

• Both target the testes in males and the ovaries in females

Ovaries

Estrogen and progesterone

Testes

Testosterone

Hormones that stimulate the Testes

Testosterone

Hormones that stimulate the Ovaries

Estrogen and Progesterone.

LH in the ovaries.

Luteinizing Hormone (LH): Causes ovulation when a surge of LH is present during menstruation

● The corpus luteum forms as a result, which produces

estrogen and progesterone

Follicle Stimulating Hormone (FSH) in the ovaries

Stimulates the growth of the follicle in ovaries

• Results in the increased production of estrogen and progesterone.

LH in the testes

Causes the production of testosterone by stimulating Leydig cells

• can make someone large and hairy.

Follcile Stimulating Hormone (FSH)

Causes the maturation of sperm by stimulating Sertoli cells.

Positive Feedback Loops

The product increases the production of the stimulus

Negative Feedback Loops

The product inhibits the production of the stimulus

Catecholamines

Short term, fast acting (amines) hormones that are in charge of fight or flight. They bind to adrenergic receptors

EX

• Norepinephrine

• Epinephrine

Mineralocorticoids

• What do they do

• Example of the most famous one?

• Increase blood volime and pressure

• Passivley allow reabsorption of water into blood

• Increase reabsorption of sodium into the excretory system

• INCRESE secretion of potassium into the execratory system

• ALDOSTERONE