Endocrinology introduction

Question 1

Classify the hormones and give examples of each

Answer 1

3 main classes

1. Steroids
   - testosterone, estrogen, and progesterone from gonads
   - cortisol and aldosterone from adrenal cortex
2. Tyrosine-derivatives (are all neurotransmitters)
   - dopamine/prolactin inhibitory factor from hypothalamus
   - T3 and T4 from thyroid gland
   - Epinephrine and norepinephrine from adrenal medulla
3. Proteins/Peptides
   - Thyroid stimulating hormone
   - LH
   - FSH

Question 2

Glands that secrete only peptides

Answer 2

Pancreas
Parathyroid glands
Anterior pituitary gland
Posterior pituitary gland

Question 3

Glands that secrete both peptides and tyrosine-derivatives

Answer 3

Adrenal gland
Thyroid gland (T3 and T4 are amines, but calcitonin is a peptide)
Hypothalamus

Question 4

Leptin is released by? Its function is to?

Answer 4

released by adipocytes. suppresses appetite and stimulates thermogenesis

Question 5

Two hormones secreted by small intestine and their functions.

Answer 5

Secretin (makes pancreatic acinar cells release water and bicarbonate)

Cholecystokinin (makes gallbladder to contract = release of pancreatic enzyme)

Question 6

Name the hormone that increases red blood cell production and its source

Answer 6

Erythropoietin - from kidneys

Question 7

Hormone released by the heart

Answer 7

Atrial natriuretic peptide

Question 8

Function of atrial natriuretic peptide.

Answer 8

Increases sodium excretion by kidneys

Causes reduction in blood pressure

Question 9

Name the hormones secreted by placenta and classify them based on their chemical structure.

Answer 9

Estrogen
Progesterone
(steroids)

Human chorionic gonadotropin
Human somatomammotropin
(peptides)

Question 10

General structure of steroids

Answer 10

3 cyclohexyl rings

2 cyclopentyl rings

Question 11

Protein that T3 and T4 bind to in plasma

Answer 11

thyroxine-binding globulin

Question 12

Which tyrosine-derivative of the adrenal medulla is secreted more than the other

Answer 12

Epinephrine secreted 4 times more than norepinephrine

*THINK: NO! = less secretion

Question 13

Hormones vary based on

Answer 13

how long it takes for them to have an effect

how long their effect lasts

Question 14

Give the unit range in which hormones exist in blood

Answer 14

from less than 1 picogram (one millionth of one millionth of a gram) to few micrograms (millionths of one gram) in 1 millimeter of blood

Question 15

LH’s effect on estrogen is an example of what type of regulation? explain

Answer 15

+ve feedback
estrogen causes surge in LH
LH in turn increases estrogen secretion

Question 16

Ways in which hormones are cleared from blood

Answer 16

Destroyed by tissues after getting endocytosed when they bind to certain receptors
By enzymes free in plasma
By being excreted as bile
By being excreted as urine via the kidneys
Binding to tissues

Question 17

Factors resulting in downregulation of receptors

Answer 17

1. Inactivation
2. Inactivation of other molecules involved in second messenger system
3. Temporary sequestering into the cell cytoplasms
4. Destruction after getting sequestered
5. Decrease in their transcription

Question 18

Outline the types of receptors through which hormones exert their actions as well as their mechanisms

Answer 18

Ion-linked cause changes by causing changes in relative ion concentrations in cells. When hormone or other ligand binds, it changes shape of ion-linked channel to allow or prevent ions from entering. few hormones use this

G-protein linked receptors indirectly cause changes in ion-linked or enzyme-linked receptors. The alpha subunit is the one that causes the effects.

Enzyme-linked are bound to enzymes or are the enzyme themselves.

Question 19

Why can one hormone have different effects on different cells?

Answer 19

Due to different machinery of the cells

Question 20

Which lipid forms the lipid part of DAG?

Answer 20

Arachidonic acid

Question 21

Mechanism of IP3 and DAG

Answer 21

IP3 diffuses into cytosol, binds to ER calcium ligand gated channels to cause release of calcium into cytosol–> formation of CAM as calcium binds to calmodulin –> CAM activates other protein kinases

DAG remains in cell membrane and activates protein kinase C which activates other proteins

Question 22

How many calcium ions must bind to calmodulin for it to exert its effects?

Answer 22

4

Question 23

State normal calcium concentration in most cells of body

Answer 23

10^-8 to 10^-7 mol/L

Question 24

By which mechanism does atrial natriuretic peptide work?

Answer 24

Uses the second messenger system via cGMP to activate protein kinase G