Welcome to Endocrinology

Question 1

What is the endocrine system?

Answer 1

A system that integrates and controls organ function via the secretion of hormones from cells, tissues or glands which are then carried in the blood to target organs

Question 2

Endocrine hormones should not be confused with what other types of hormones?

Answer 2

Paracrine - acting on local sites
Autocrine - acting within the same cell
Exocrine - secreted into ducts

Question 3

How do hormones enact specific responses in different target tissues?

Answer 3

Specific receptor (either GPCR or tyrosine kinase coupled)

Question 4

What is the definition of a neuroendocrine system?

Answer 4

A system where the nervous system and endocrine system combine e.g. hypothalamic-posterior pituitary axis

Question 5

What three types of endocrine hormones are there?

Answer 5

1. Peptide hormone
2. Steroid hormone
3. Amine hormone

Question 6

What can be said about the solubility of peptide hormones?

Answer 6

Water-soluble

Question 7

How does the solubility of peptide hormones affect their storage?

Answer 7

Can be bound in vesicles

Question 8

How are peptide hormones synthesised?

Answer 8

Initial protein produced by ribosomes as large, inactive preprohormones.

Packed into vesicles by the Golgi apparatus along with proteolytic enzymes which convert the preproxhormones into prohormones ready for secretion.

Question 9

When a prohormone is cleaved, it leaves fragments, how are these clinically relevant?

Answer 9

Measuring the concentration of the fragments may be helpful diagnostically (e.g. C-peptide as a fragment of endogenous insulin)

Question 10

How are steroid hormones produced?

Answer 10

As needed, due to their lipophilic nature they cannot be contained in cell membranes.

Question 11

How do steroid hormones travel in the body?

Answer 11

Bound in complex with proteins like albumin.

Question 12

What effect does the albumin-hormones complex have on the lifespan of a hormone?

Answer 12

Protects it from enzymatic damage and extends their life (60-90 mins vs 2 mins for amine hormones)

Question 13

What organs secrete steroid hormones?

Answer 13

Gonads, Placenta, kidneys, adrenal cortex

Question 14

How do steroid hormones bring about a response in target tissues?

Answer 14

Intracellular receptors have a genomic effect

Question 15

What are all steroid hormones derived from?

Answer 15

Cholesterol

Question 16

What are all amine hormones derived from?

Answer 16

Tryptophan or tyrosine

Question 17

What can be said about the lifespan of catecholamine and peptide hormones?

Answer 17

Short-lived and excreted easily

Question 18

What can be said about the lifespan of steroid and thyroid hormones?

Answer 18

Take a long time to excrete as they are protein bound

Question 19

What mechanisms control the secretion of hormones?

Answer 19

1. Negative feedback
2. Neural feedback
3. Up-regulation/down-regulation
4. Permissive effects
5. Antagonistic effects

Question 20

What is up-regulation?

Answer 20

After long exposure to low hormone concentrations, up-regulation occurs and increases the number of hormone receptors on the target tissue (increasing its sensitivity)

Question 21

What is a permissive effect?

Answer 21

The presence of one hormones enhances the effect of another (e.g. cortisol has a permissive effect on epinephrine)