Hormone Basics Flashcards
Endocrine signals are characterized by the relationship between the site of secretion and the relative location of target receptors.
What is autocrine secretion?
Released signal affects the cell from which it was secreted
Endocrine signals are characterized by the relationship between the site of secretion and the relative location of target receptors.
What is Paracrine secretion?
Signal acts on neighboring cells with appropriate receptors
Endocrine signals are characterized by the relationship between the site of secretion and the relative location of target receptors.
What is Endocrine secretion?
Signal enters the bloodstream and acts on distant receptors
Endocrine signals are characterized by the relationship between the site of secretion and the relative location of target receptors.
What is Exocrine secretion?
Released signal enters a duct and acts on epithelial surface of skin/gut
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?
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.
Discuss synthesis and movement of hormones that are peptide/protein based
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)
Discuss synthesis and movement of hormones that are steroid based
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
What the hell are amine based hormones?
These guys are made from tyrosine precursors. They can act like steroids or like protein hormones.
These carrier proteins that help our nonsoluble steroid hormones are made where?
The liver
For the carrier protein Corticosteroid-binding globulin, what hormones does it help to transport, and what conditions affect its concentrations?
This guy transports cortisol and aldosterone.
It is decreased in cirrhosis, nephrotic syndrome, and hypothyroidism
For the carrier protein Sex hormone-binding globulin, what hormones does it help to transport, and what conditions affect its concentrations?
This guy transports estrogen and testosterone (big stretch, huh)
It is increased by estrogen, OCPs (oral contraceptives) and exogenous thyroid hormone
For the carrier protein Thyroxine-binding globulin, what hormones does it help to transport, and what conditions affect its concentrations?
This guy binds and transports Thyroxine (T4) and Triiodothyronine (T3).
It is increased by estrogen, pregnancy, and OCPs
For the carrier protein Serum Albumin, what hormones does it help to transport, and what conditions affect its concentrations?
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
What would an increase in sex hormone-binding globulin do to males? Why?
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.
Discuss the adenylate cyclase second messenger system
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.
Inhibitors of the adenylate cyclase mechanisms
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
What hormones use the adenylate cyclase pathway?
FLAT CHAMP
FSH LH ACTH TSH CRH hCG ADH (V2 receptor) MSH PTH
As well as Calcitonin and Glucagon
Discuss the Inositol Triphosphate (IP3) mechanism
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
What hormones use the IP3 pathway?
GGOAT
GnRH GHRH Oxytocin ADH (V1 receptor) TRH
Hypothalamic and posterior pituitary hormones use this messenger pathway
IP3 pathway
Except for Corticotropin releasing hormone (CRH), which uses AC.
Anterior pituitary hormones use what messenger pathway?
cAMP via AC
Discuss the Receptor Tyrosine Kinase Mechanism for second messengers
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.
What hormones use the receptor tyrosine kinase pathway?
Insulin VEGF PDGF EGF FGF IGF-1
Discuss the JAK/STAT second messenger pathway
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
