Endocrine-Intro

Question 1

Give 3 important endocrinology disease in vet med

Answer 1

Hyperthryoidism
-Seen in older cats

Hyperadrenocorticism (Cushing’s disease)
-Seen in dogs and horses

Hypothyroidism
-Seen in dogs

Question 2

Define endocrinology

Answer 2

Signaling through chemicals made in one cell type (endocrine cell) that enters circulation (blood). Hormones travel to distant targets and bind to specific receptors. Binding to receptors leads to an effect in the target cell via signal transduction.

Question 3

Give some non-classic endocrine tissues

Answer 3

Kidney
Heart
Fat
GI tract
Tumor

Question 4

Give example of non-classic endocrine hormone production

Answer 4

Sometimes when there is hypercalcemia, it is due to a tumor making parathryoid like peptide (PTHrP) that acts like PTH to elevate blood Ca2+

This is called paraneoplastic syndrome

Question 5

Give 3 general hormone traits

Answer 5

• Circulate in LOW amounts
• Have relatively SHORT half-lives
• Act on SPECIFIC receptors

Question 6

What type of feedback is more common in endocrine system?

Answer 6

Negative feedback

Positive feedback occurs but is less common and unstable

Question 7

2 drives of negative feedback

Answer 7

• Physiologically driven: responds to non-hormone signal

- Endocrine axis driven: responds to a hormone

Question 8

Give examples how negative feedback is physiologically driven

Answer 8

1-As glucose increases, insulin receptors increase which causes a decrease in glucose in blood.

2-Low Ca2+ in blood will cause PTH to increase which causes increase n Ca2+ in blood. Increase of Ca2+ will cause decrease of PTH.

Question 9

Give examples how negative feedback is endocrine axis driven

Answer 9

1-Cortisol from adrenal is released in response to release of ACTH from pituitary. Increased cortisol suppresses ACTH

2-Testosterone released in response to LH from pituitary. Hugh testosterone then suppresses LH

Question 10

Explain how evaluating hormone feedback can be used to diagnose diseases

Answer 10

Insulinoma or pancreatic beta cell problem

Beta cells in pancreas secrete insulin. If tumor in beta cells, there can be oversecretion of insulin AND loss of feedback control. So you can get depletion of glucose in blood due to so much insulin and insulin levels stay high. No negative feedbck to shut off insulin secretion.

Hypoglycemic

Question 11

How would you diagnose hypoglycemia?

Answer 11

Fast patient and measure glucose and insulin levels. Low glucose levels in conjunction with high insulin during fasting indicates disease.

-Patient would appear very weak

Question 12

What is a drug that can be given to test if patient has Cushing’s? How?

Answer 12

Dexamethasone-Dex is a glucocorticoid that resembles cortisol but more potent.

• When patient has Cushings, they have an xs amount of ACTH from pituitary and xs amount of cortisol from adrenal glands.
• When Dex is given, it will shut off ACTH (because it resembles cortiosl and there is negative feedback relation btw ACTH and cortisol). Shutting of ACTH will then shut off cortisol production in adrenal glands in couple of hours.

Question 13

What would happen btw TSH and T4 relationship if pituitary was damaged?

Answer 13

There would be loss of TSH (made from pituitary)

-So you wouldn’t get TSH OR T4

Question 14

What would happen btw TSH and T4 if thyroid was removed?

Answer 14

Loss of T4 secretion (from thyroid) so you wouldn’t have negative feedback and nothing to signal decrease TSH so you would get xs TSH.

Question 15

Who drives who in TSH vs T4?

Answer 15

TSH from pituitary.

Question 16

4 chemical classifications of hormones

Answer 16

1-Protein/polypeptide/peptide: 3+ A

2-Steroid: from cholestrol

3-Modified AA: AA + catecholamine (normally tyrosine + norepinephrine +epinephrine)

4-FA: prostaglandin

Question 17

Examples of protein/PP hormones

Answer 17

Insulin
PTH
GH

Question 18

Explain production and release of protein hormones

Answer 18

Made in endocrine cell from specific gene transcription/translation and stored in secretory vesicles

Released by exocytosis

Question 19

Do protein hormones have long half lives? how do they circulate?

Answer 19

Short halflives

circulate freely (unbounded)
Exception: GH, IGF

Question 20

Target cells of protein receptors have what type of receptors?

Answer 20

Surface cell receptors

Question 21

Give common signal transduction pathways for protein hormones once they bind to target cell receptor

Answer 21

cAMP
Phospholipid
Ca2+/calmodulin
Tyrosine kinase

Question 22

Signal transduction pathways utilize…

Answer 22

GPCR (cAMP, DAG,IP3)

Jak-Stat signaling (GH, prolactin…involves phosphorylation of tyrosines)

Question 23

How are protein hormones usually administered?

Answer 23

Injections NOT oral (GIT interferes)

Question 24

Example of clinical relevance of a protein hormone

Answer 24

Hyperparathyroidism due to PT tumor and causes hypercalcemia due to xs PTH
–>Need to remove 1/4 PT glands…if PTH drops by 50% after surgery then can confirm tumor was removed.

Question 25

Steroids are made from

Answer 25

Cholesterol which is sourced from the blood and taken up by endocrine cells.

Question 26

Give some major steroid producing endocrine tissue

Answer 26

``` Adrenal cortex Ovary Testes Liver Kidney (vitamin D) ```

Question 27

How are steroids similar/different from each other?

Answer 27

Have same base ring but different #C, C=C binding, and different R groups -->Cholesterol is same precursor

Question 28

Are steroids water soluble? 1/2 lives?

Answer 28

No Long half lives (bounded)

Question 29

How are steroid receptors different from protein hormone receptors?

Answer 29

Steroid receptors are INSIDE target cell-nuclear receptor. Protein hormones are on cell surface. Steroids act slower than protein hormones because they alter gene transcription but effects last longer than protein hormones.

Question 30

Steroid and thyroid receptors

Answer 30

Share basic structure and can "cross-talk" and hormone can bind to several receptors

Question 31

How can steroids be administered?

Answer 31

Oral, injectable, spray, etc

Question 32

Modified AA hormone examples

Answer 32

Thyroid hormones T4 and T3 Catecholamines epinephrine and norepinephrine

Question 33

How are T3 and T4 made? Describe traits

Answer 33

Conjugation and iodination of tyrosine | -Insoluble, carrier proteins used, given orally, intracellular receptors used

Question 34

How are epinephrine and norepinephrine made? Describe traits?

Answer 34

Derived from tyrosine and made in adrenal medulla | -Unbound and bind to cell surface receptors

Question 35

How are protein hormones made?

Answer 35

Gene transcription/translation

Question 36

How are steroids made?

Answer 36

Conversion from cholesterol

Question 37

How are modified AA made?

Answer 37

Modification of 1 or 2 AA (tyrosine)

Question 38

What amount of protein hormones are stored in endocrine cells?

Answer 38

High

Question 39

What amount of steroids are stored in endocrine cells?

Answer 39

Low

Question 40

What amount of modified AA are stored in endocrine cells?

Answer 40

High-moderate

Question 41

Mechanism of action of protein hormones?

Answer 41

Cell surface receptors

Question 42

Mechanism of action of steroids

Answer 42

Intracellular receptors

Question 43

Mechanism of modified AA

Answer 43

Intracellular receptors and cell surface receptors

Question 44

Identical structure btw species of protein hormones?

Answer 44

Variable, yes and no - If you compare particular hormone structurally among different species, you'll see diff series of AA - ->Eample GH in bovine vs man...Ab won't recognize diff spp of GH

Question 45

Identical structure btw species of steroids?

Answer 45

Yes | -Cortisol same across all spp

Question 46

Identical structure btw species of modified AA?

Answer 46

Yes | -T4 same across all spp

Question 47

Examples of protein hormones

Answer 47

ACTH Insulin

Question 48

Examples of steroids

Answer 48

Estrogen cortisol

Question 49

Examples of modified AA

Answer 49

T3 and T4 Catecholamines

Question 50

Are most steroids and thyroid hormones in blood bound or free?

Answer 50

Bound to carrier proteins

Question 51

Binding proteins allow

Answer 51

Increase in 'total' amount of hormone in circulation and acts as a reservoir or buffer and may help distribute the hormone as blood diffuses across tissue

Question 52

Is free or bound form of hormone biologically active?

Answer 52

Free

Question 53

What is usually measured in hormones?

Answer 53

Total hormones because free is more expensive. Although, free gives a better view of what is wrong. -If abnormal free hormone levels seen, probs problem in endocrine system

Question 54

Disease in free vs total hormone

Answer 54

In disease, free hormone will adjust to its normal concentration however, total hormone concentration may be altered.

Question 55

Concentration of free hormone=

Answer 55

total concentration X % free

Question 56

% free hormone =

Answer 56

% total that is free

Question 57

The more binding protein present, what do you see in % free and secretion?

Answer 57

Lower % free and increase secretion

Question 58

THe less binding protein present, what do you see in $ free and secretion

Answer 58

Increase % free and decrease in secretion

Question 59

How can you measure hormones in circulation?

Answer 59

Radioimmunoassay -Use radioactive tag on hormone w/AB and hormone not tagged w/AB You don't know how much hormone in patient sample but you know amount of radioactivity so you can determine amount of hormone based on amount of binding sites. -->Two-site RIA detects intact proteins

Question 60

Give some traits of hypofunction endocrine disease

Answer 60

Often due to autoimmune disease Gradual loss of tissue Feedback activated, signs develop when threshold reached

Question 61

Give some traits of hyperfunction endocrine disease

Answer 61

Often due to hyperplasia or tumor, usually benign | Autonomonus fxn, abnormal feedback