Introduction to Endocrinology

Question 1

Define homeostasis.

Answer 1

The process by which internal systems of the body are maintained within optimum parameters despite variations in external conditions

Question 2

List 3 short-term effects of the endocrine system.

Answer 2

Blood pressure, pH of intracellular and extracellular fluid, respiration

Question 3

List 3 long-term effects of the endocrine system.

Answer 3

Growth, reproduction, metabolism

Question 4

Give the definition of a hormone.

Answer 4

A substance produced by glands with internal secretion, which serve to carry signals through the blood to target cells and organs

Question 5

Give the definition of paracrine hormones.

Answer 5

Hormones that are produced by endocrine tissue and diffuse out of the cell to be transmitted through extracellular fluid to alter the structure or function of adjacent target cells

Question 6

Give the definition of autocrine hormones.

Answer 6

Hormones that are produced by a cell and act locally on the same cell

Question 7

What is the diffuse endocrine system and give examples?

Answer 7

A network of endocrine cells that are scattered throughout the body and not found in discreet glands, such as G cells of the stomach and the juxtaglomerular cells of the kidney

Question 8

What are the 3 main types of stimuli that regulate hormone secretion?

Answer 8

Hormonal stimuli, humoral stimuli, neural stimuli

Question 9

What is hormonal regulation of hormone secretion and give an example.

Answer 9

Hormones released in response to another hormone – hypothalamic-pituitary-thyroid-axis

Question 10

What is humoral regulation of hormone secretion and give an example.

Answer 10

Changes in the concentration of certain ions and nutrients in the blood regulate hormone release – insulin and glucagon by the pancreas in response to blood glucose

Question 11

What is neural regulation of hormone secretion and give an example.

Answer 11

Nervous system directly stimulates the release of hormones – release of catecholamines (adrenaline) from the adrenal medulla

Question 12

What are the 3 main classes of hormone?

Answer 12

Peptides, steroids, amines

Question 13

How are peptide hormones synthesised and released?

Answer 13

Synthesised from amino acids and secreted via exocytosis when calcium enters the cell causing the granule membrane to fuse with the cell membrane

Question 14

Are peptide hormones water-soluble or lipid-soluble?

Answer 14

Water-soluble

Question 15

What are some examples of peptide hormones? (7)

Answer 15

TRH, TSH, insulin, glucagon, CCK, prolactin, parathyroid hormone

Question 16

How are steroid hormones synthesised?

Answer 16

They are derived from cholesterol. Cholesterol is converted into pregnenolone by the enzyme desmolase in the mitochondria

Question 17

Are steroid hormones water-soluble or lipid-soluble?

Answer 17

Lipid-soluble

Question 18

What are some examples of steroid hormones? (5)

Answer 18

Oestrogen, testosterone, progesterone, cortisol, aldosterone

Question 19

What are amine hormones derived from?

Answer 19

Derivatives of the amino acids tyrosine and tryptophan

Question 20

How are amine hormones released?

Answer 20

Exocytosis

Question 21

What are some examples of amine hormones? (2)

Answer 21

Thyroid hormones and adrenaline

Question 22

Are amino hormones water-soluble or lipid-soluble?

Answer 22

They may be water-soluble or lipid-soluble

Question 23

What are the 3 functions of hormone-binding proteins?

Answer 23

Increase solubility of thyroid hormones and steroid hormones

Protects hormones from renal filtration and peripheral metabolism, increasing their plasma half-life.

Create an accessible pool of hormones to stabilize free hormone levels

Regulate their availability to target tissues.

Question 24

What is the role of cell-surface receptors and which type of hormones use them?

Answer 24

Cell-surface receptors span the membrane, transmitting hormone signals through signal transduction. Water-soluble hormones, which cannot cross the membrane, use these receptors

Question 25

What are the 2 types of cell-surface receptors in the endocrine system?

Answer 25

G-protein coupled receptors (adenylyl cyclase

Phospholipase C mechanisms), tyrosine kinase receptors

Question 26

Which type of hormones use intracellular receptors?

Answer 26

Hormones that readily cross the cell membrane, such as steroid and thyroid hormones

Question 27

What happens when a hormone binds to an intracellular receptor?

Answer 27

The receptor changes shape and activates, allowing the hormone-receptor complex to enter the nucleus and bind to specific DNA sections, affecting gene transcription and protein synthesis

Question 28

What happens to the response of a target tissue as hormone concentration increases?

Answer 28

The response increases as hormone concentration increases but eventually levels off

Question 29

How can the sensitivity of a target tissue be changed?

Answer 29

By altering the number of receptors or changing the affinity of the receptors for the hormone

Question 30

What is primary endocrine dysfunction?

Answer 30

A problem with the endocrine gland itself, where it secretes too much or too little hormone despite normal stimuli

Question 31

What is secondary endocrine dysfunction?

Answer 31

A problem with the hormonal or humoral stimulus, with excess stimulus resulting in too much hormone secretion and lack of stimulus resulting in too little hormone secretion