Hormones Flashcards
Agonist
drug that binds to a receptor and mimics the normal ligand action (e.g. isoproterenol acts like adrenaline at beta adrenoreceptors - treat bradycardia, slow heart rate)
antagonist
prevents the action of a hormone
Clinical uses of hormones
Insulin to treat diabetics Anticancer therapies (block testosterone action for prostate cancer with flutamide (prostate cancer is testosterone responsive))(block estrogen action for breast cancer with FASLODEX (fulvestrant) an estrogen receptor antagonist (competes for binding site))
Types of hormones
endocrine - made in one tissue and travel to target organ, paracrine - made in a cell and travel short distance, autocrine - made and functions in same cell (or nearby)
Peptide - includes growth factors, amino-acid derived hormones, usually water soluble, bind cell surface receptors
Steroid - membrane permeable, bind intracellular receptors
Endocrine hormones
insulin is an example made in one tissue travel to target organ through blood receptor-expressing cells Tend to be stable, larger amounts, longer half-life
Paracrine hormones
Acetylcholine is an example Made in a cell Travels a short distance Bind receptors on neighboring cells Smaller amounts, shorter half life
Autocrine hormones
Nitric oxide is an example
Made and functions in same cell or near by
small amount, short half life
Peptide hormones
Includes growth factors, amino-acid derived hormones
Usually water soluble, bind cell surface receptors
Insulin, glucagon, adrenocorticotropin hormone (ACTH) are examples
Steroid hormones
Membrane permeable (lipid soluble)
Bind intracellular receptors
Adrenal hormones: Cortisol (glucocorticoid), aldosterone (mineralcorticoid)
Sex and Progestational hormones: 17 beta estradiol (estrogen), testosterone (androgen), and progesterone (progestin) are examples
Derived from cholesterol
Things to remember about hormones that bind to cell surface receptors
The binding is tight
It is swift and reversible
Receptor specificity and affinity for hormone is high
Examples of basic signal transduction mechanisms include:
- Receptor coupled to adenylate cyclase (cAMP)
- Receptor kinase activity (phosphorylation)
- Receptor coupled to hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2)
Endogenous production of insulin can be detected by:
presence of C-peptide
Human insulin analogs
Lispro and Aspart (short-acting and rapidly absorbed), Glargine (long-acting, peakless, low rates of hyperglycemia)
Insulin signaling
Tyrosine kinase receptor
phosphorylates itself and IRS
allows binding of proteins with SH2 domains (Grb2 and PLCgamma)
activates PI3 kinase
Activates protein kinase B (also called Akt)
Epinephrine receptors
Epinephrine binds alpha-adrenergic receptors and beta-adrenergic receptor
In the liver, epinephrine acts through G proteins and PIP2 signaling (IP3 causes release of calcium)
In muscle, epinephrine acts through cAMP signaling
Phosholipase C is involved, as well as Protein kinase C. Calmodulin-dependent protein kinase and phosphorylase kinase are activated, which inactivate glycogen synthase and activate glycogen phosphorylase
Glucagon effects
acts through cAMP
Glucagon leads to inhibition of glycogen synthase
uses G protein, cAMP, Active protein kinase A
Examples of second messengers are Calcium, cAMP, diacylglycerol, and inositol triphosphate
(Epinephrine and glucagon work in similar ways)
Transport of steroids
Plasma albumin is a nonspecific carrier
Transcortin (aka cortico-steroid binding globulin) transports cortisol and corticosterone
Sex-hormone binding globulin carries testosterone and 17-beta estradiol
All steroid hormones are synthesized from __.
cholesterol
Hormone synthesizing enzymes are activated by __.
FSH, ACTH, and LH
ACTH, FSH, and LH activate ___.
hormone synthesizing enzymes
A cholesterol esterase to produce rapid supply of cholesterol
Synthesis of LDL receptors
ACTH activates ____.
cortisol synthesis
Cortisol synthesis is activated by ___.
ACTH