Hormone Basics

Question 1

Endocrine signals are characterized by the relationship between the site of secretion and the relative location of target receptors.

What is autocrine secretion?

Answer 1

Released signal affects the cell from which it was secreted

Question 2

Endocrine signals are characterized by the relationship between the site of secretion and the relative location of target receptors.

What is Paracrine secretion?

Answer 2

Signal acts on neighboring cells with appropriate receptors

Question 3

Endocrine signals are characterized by the relationship between the site of secretion and the relative location of target receptors.

What is Endocrine secretion?

Answer 3

Signal enters the bloodstream and acts on distant receptors

Question 4

Endocrine signals are characterized by the relationship between the site of secretion and the relative location of target receptors.

What is Exocrine secretion?

Answer 4

Released signal enters a duct and acts on epithelial surface of skin/gut

Question 5

Endocrine signals are characterized by the relationship between the site of secretion and the relative location of target receptors.

What do we mean with the category Multifunctional signals?

Answer 5

These signals have effects in multiple categories, causing different effects based on target tissue.

Like testosterone, which acts on muscle to stimulate growth (endocrine) and on seminiferous tubules to promote spermatogenesis.

Question 6

Discuss synthesis and movement of hormones that are peptide/protein based

Answer 6

Preprohormone typically synthesized by the rough ER. Signal peptide cleavage in the RER produces the prohormone. Then, transport within the golgi apparatus results in further processing and final active hormone structure, which gets stored in secretory vesicles and released via exocytosis into the blood stream (water-soluble).

Act on cell surface receptors and second messenger systems of target tissues (fast acting effects)

Question 7

Discuss synthesis and movement of hormones that are steroid based

Answer 7

These hormones are synthesized from cholesterol on demand (not stored) by the smooth ER, not the Rough ER like we see with protein based hormones. The lipid solubility allows for rapid diffusion of these hormones across the membrane.

They are transported in blood like peptide hormones, but they are bound to plasma carrier protiens since they are not readily soluble.

They diffuse across the target cell membrane and bind to intracytoplasmic protein receptors, not the receptors on the target membrane like we see with peptide hormones.

The resultant steroid hormone-receptor complex enters the nucleus and activates transcription of specific genes for new protein synthesis (slow-acting effects), unlike protein hormones which propagate their signal via second messengers

Question 8

What the hell are amine based hormones?

Answer 8

These guys are made from tyrosine precursors. They can act like steroids or like protein hormones.

Question 9

These carrier proteins that help our nonsoluble steroid hormones are made where?

Answer 9

The liver

Question 10

For the carrier protein Corticosteroid-binding globulin, what hormones does it help to transport, and what conditions affect its concentrations?

Answer 10

This guy transports cortisol and aldosterone.

It is decreased in cirrhosis, nephrotic syndrome, and hypothyroidism

Question 11

For the carrier protein Sex hormone-binding globulin, what hormones does it help to transport, and what conditions affect its concentrations?

Answer 11

This guy transports estrogen and testosterone (big stretch, huh)

It is increased by estrogen, OCPs (oral contraceptives) and exogenous thyroid hormone

Question 12

For the carrier protein Thyroxine-binding globulin, what hormones does it help to transport, and what conditions affect its concentrations?

Answer 12

This guy binds and transports Thyroxine (T4) and Triiodothyronine (T3).

It is increased by estrogen, pregnancy, and OCPs

Question 13

For the carrier protein Serum Albumin, what hormones does it help to transport, and what conditions affect its concentrations?

Answer 13

This guy is a non specific steroid transporter, and also specifically transports T4 and T3.

We see it decreased in cirrhosis, nephrotic syndrome, and protein malnutritions

Question 14

What would an increase in sex hormone-binding globulin do to males? Why?

Answer 14

Carrier proteins allow for another level of control within the signaling network, as hormone-protein complexes are unable to diffuse across membranes and activate target cells. Instead, free and bound forms of hormone exist in equilibrium, and only free hormone is biologically active.

SHBG decreases free testosterone by binding it up for transport, which increases the amount of unopposed estrogen activity, and can lead to gynecomastia.

Question 15

Discuss the adenylate cyclase second messenger system

Answer 15

Hormone binds G-protein coupled receptors (GPCR), which then stimulates Adenylate Cyclase.

AC catalyzes formation of cAMP from ATP. cAMP activates protein kinase A, which phosphorylates other proteins.

Question 16

Inhibitors of the adenylate cyclase mechanisms

Answer 16

Typically while we are activating this system, the GPCR we are hitting is a GPCRs (stimulatory).

If a hormone hits the GPCRi (inhibitory), then we get an inhibition of AC.

Furthermore, we can directly inhibit cAMP by inactivating it with phosphodiesterase

Question 17

What hormones use the adenylate cyclase pathway?

Answer 17

FLAT CHAMP

FSH
LH
ACTH
TSH
CRH
hCG
ADH (V2 receptor)
MSH
PTH

As well as Calcitonin and Glucagon

Question 18

Discuss the Inositol Triphosphate (IP3) mechanism

Answer 18

Hormone binds GPCR and activates the G protein (Gq), which stimulates phospholipase C.

Phospholipase C cleaves phosphatidylinositol 4,5-bisphosphate (PIP2) a membrane lipid, producing IP3 and diacylglycerol (DAG).

IP3 opens calcium channels in endoplasmic reticulum, releasing calcium into the cytoplasm.

DAG and calcium facilitate activation of protein kinase C, which phosphorylates other proteins

Question 19

What hormones use the IP3 pathway?

Answer 19

GGOAT

GnRH
GHRH
Oxytocin
ADH (V1 receptor)
TRH

Question 20

Hypothalamic and posterior pituitary hormones use this messenger pathway

Answer 20

IP3 pathway

Except for Corticotropin releasing hormone (CRH), which uses AC.

Question 21

Anterior pituitary hormones use what messenger pathway?

Answer 21

cAMP via AC

Question 22

Discuss the Receptor Tyrosine Kinase Mechanism for second messengers

Answer 22

This hormone binds two receptors at once that are adjacent in the cell membrane, activating a receptor dimer with tyrosine kinase activity.

The intracytoplasmic ends of this receptor dimer cross phosphorylate eachother as well as other proteins, some of which are more tyrosine kinases which can further spread phosphorylation of proteins.

Question 23

What hormones use the receptor tyrosine kinase pathway?

Answer 23

Insulin
VEGF
PDGF
EGF
FGF
IGF-1

Question 24

Discuss the JAK/STAT second messenger pathway

Answer 24

With this, a hormone binds two identical cell membrane receptors, activating JAKs on cytoplasmic ends. The JAKs phosphorylate tyrosine residues on receptors, and also recruit and phosphorylate STATs.

Activated STATs dimerize and translocate to the nucleus to modify gene expression

Question 25

What hormones use the JAK/STAT pathway?

Answer 25

Growth Hormone
Prolactin
Leptin
Erythropoetin
Thrombopoetin
GM-CSF
Interferons
Most interleukins

Question 26

What hormones use intracellular receptors?

Answer 26

Aldosterone
Estrogen
Testosterone
Progesterone
Vitamin D
Triiodothyronine

All steroid based as you might guess except for Triio which is an amine one, but recall that amine hormones can do things in both peptide and steroid hormone categories.