Basics of Endocrinology I Flashcards Preview

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Flashcards in Basics of Endocrinology I Deck (51):

What is the defining feature of classic endocrine glands?

They are ductless!


Where do the secrete hormones?

Directly into the blood or extracellular spaces


What are the non-classical endocrine glands?

Brain (esp. hypothalamus), Kidneys, Heart, Liver, GI, Adipose Tissue


What is the endocrine function of the the brain?

"releasing hormones"


What is the endocrine function of the kidneys??

Release of renin, Vit. D, EPO


What is the endocrine function of the heart?

release of ANP/BNP


What is the endocrine function of the liver?

Release of IGF-1 (insulin like growth factor-1)


What is the endocrine function of GI tissue?

stomach, small GI release serotonin, ghrelin


what is the endocrine function of adipose tissue?

Release of leptin


Discuss the concept of homeostasis in regards to hormones

There is a balance of hormones in the body - hormones are always present, in a regulated amount. Too much or too little of a given hormone can cause problems


What can give a hyper response to a hormone?

Too much of the hormone or too much of the hormone receptor


What can give a hypo response?

Too little hormone or too little receptor


What are endocrine pathologies characterized by?

A hormone imbalance


Where can the defect be in an endocrine pathology?

At the level of the gland --> primary
One or two steps away --> secondary/tertiary


Give an example of and describe an endocrine pathology that is congenital

Cretinism: due to an iodine deficiency during development

results in: short stature, mental retardation, delayed motor development


Give an example of and describe an endocrine pathology that is genetic

Multiple Endocrine Neoplasia (MEN): Characterized by 2-3 tumors in multiple endocrine glands (parathyroid, pituitary, entero-pancreatic)


Give an example of and describe an endocrine pathology that can give rise to malignant or benign tumors

Neoplastic tissues, small lung cell carcinoma


Give an example of and describe an endocrine pathology stemming from an infection/immunological problem

autoimmune - Diabetes type I


Give an example of and describe an endocrine pathology stemming from environmental factors

PCBs, DES, birth control


Give an example of and describe en endocrine pathology stemming from trauma/stress

Sheehan's syndrome: postpartum hemorrhage and shock - results in massive pituitary death


Give an example of and describe an endocrine pathology related to surgery

Thyroid gland removal (often parathyroid injury)


Give an example of and describe an endocrine pathology stemming from a therapy

Glucocorticoids (Crohn's disease, others)


What is the most common endocrine pathology, and what are some important facts about it?

Type II diabetes!

7th leading cause of death
affects 9.3% of population (2 mil new cases per year)
highly correlated with obesity


Define endocrine action

Hormone release into the blood, acting on downstream tissue


Define paracrine action

Hormone released into the interstitial space, acting on nearby cells


Define autocrine action

Hormone released into the interstitial space that will act on the same cell that released it


Discuss some differences in the regulation of hormone action between endocrine and paracrine signaling in regards to the source and distribution of the hormone

endocrine - gland, no specificity to target
paracrine - adjacent cell, major determinant of target

Endocrine - Universal, dilution big
Paracrine - ECM, binding proteins, diffusion distance, proteases


What are things to consider regarding the signal being passed to the target cell?

specificity/sensitivity, # of receptors, downstream pathways, metabolism of receptors, other ligands, inhibitory pathways, etc.


What class of hormones are usually attached to hormone binding proteins in the blood?



What are the hormones other than steroids that bind to hormone binding proteins?

IGF-1, GH, T4/T3


What is the purpose of hormone binding proteins?

Increases the half life of the hormone


What is a pharmacological consequence of hormone binding proteins?

Bound hormones are not active and as some are released right at the target site, you may not see any measurable free/active hormone in the blood


What does sex hormone binding globulin (SHBG) bind?

estrogens and testosterone


What does corticosteroid binding globulin (CBG) bind?

cortisol and corticosterone


What does thyroxine binding globulin (TBG) and transthyretin (TTR) bind?

thyroid hormone


What does albumin bind?

most lipophilic compounds in blood


What is notable about hormones bound to albumin?

They are bioavailable!


Discuss the two methods of hormone delivery to their target

The hormone can be released at the cell surface, translocate the plasma membrane, and exert its effect on the cell

Or, the hormone/protein complex binds to megalin, there is the formation of an endocytic vesicle, after which the hormone will dissociate and e released from the vesicle


Why would a cell undergo the vesicle delivery of hormone?

The vesicle could be targeted to a specific part of the cell

Protects the hormone from degradation


Describe some features of hormone receptors

no receptor = no action (antagonist, agonist)

determines duration: extracellular receptors are internalized and dissociated, internal receptors are ubiquinated

autoregulation by ligand: up/down regulated based on ligand levels


With what specificity and affinity do hormones bind their receptors?

High affinity and high specificity


Define specificity

ability to distinguish between similar substances


Define affinity

How much a receptor will hold on to a ligand once bound

measured as Kd: ligand concentration at which 50% of binding sites are filled (smaller number = higher affinity)

Ki: ability to displace ligand at 50% maximal activity


What are some general features of lipophobic receptors, and what are the different classes?

Bind to cell surface receptors

coupled to second messenger pathways like cAMP, IP3, DAG

rapid internalization/degradation

1: Ion channels
2: G-protein coupled
3: Receptor-linked Kinases
4: Receptor Kinases


Discuss the features and function of cell surface class 1 ion channels

binding of ligand causes conformational change that results in opening of channel

Neurotransmitters typically activate these types of receptors


Discuss the features and functions of cell surface class 2 G-protein coupled receptors

Most protein and peptide hormones bind to this kind of receptors

Ligand binding activates second messenger signaling cascades


Discuss the features and functions of cell surface class 3 receptor-linked kinases

DO NOT have intrinsic catalytic activity

Ligand binding results in dimerization, activates the intracellular kinase

examples: GH, prolactin, EPO


Discuss the features and functions of cell surface class 4 receptor kinases

Have intrinsic catalytic activity that is stimulated by ligand binding - autophosphorylation on intracellular domain

Insulin and atrial natriuretic peptide bind to this kind of receptor


What are some general functions of lipophilic hormone receptors

Bind mainly to intracellular receptors

often attached to large chaperone proteins in the cytoplasm (heat shock proteins)

usually slow biological response - requires transcription/translation

can repress or activate transcription


What is an example of a lipophilic hormone?

Thyroid hormone binds nuclear receptor, when receptor binds ligand there is gene activation


What are the factors affecting hormone bioavailability?

Hormone transport: binding proteins and kinetics

Target tissues: receptor regulation and chaperone/heat shock proteins

Hormone synthesis/release: enzymatic activity and processing/packaging

Regulatory mechanisms: eedback, circadian rhythms, aging, pulsatility, metabolism/degradation