Intro to Endocrinology

Question 1

Endocrine v. paracrine v. autocrine v. juxtacrine

Answer 1

Endocrine: one cell makes something that goes through blood to signal another cell

Paracrine: a cell nearby siganls another cell

Autocrine: cell signals itself

Juxtacrine: cells that touch each other signal

Question 2

Which organs are involved in endocrine system?

Answer 2

Hypothalamus

Pituitary

Thyroid

Parathyroid

Pancreas

Adrenal

Gonads

Question 3

3 classes of hormones

Answer 3

Peptides and protein

Steroids: derivatives of cholesterol

Amines: derivatives of tyrosine

Question 4

Peptide hormone: how is it made?

Answer 4

1. nucleus: gene –> mRNA
2. mRNA –> cytoplasm –> ribosomes –> preprohormone
3. translation continues in ER –> entire peptide is made
4. signal peptide is removed in ER, converting it to a prohormone
5. in Golgi, it’s packaged into secretory vesicles & cleave off some peptide sequences to make the final hormone

** stored in secretory vesicles until endocrine cell is stimuate

i.e. PTH is stored until low extracellular calcium –> sensors on parathyroid gland sense this –> secretory vesicles translocated to cell membraen & PTH is released via exocytosis

Question 5

Steroid hormones: synthesis & secretion

Answer 5

Cholesteron –> aldo, cortisol, androgens, Vitamin D, etc. (adrenal cortex, gonads, corpus luteum, placenta)

Question 6

Amines

Answer 6

i.e. dopamine, norepi, epi, T3, T4

Tyrosine derivatives

Question 7

Which receptors do different hormones act throuhg?

Answer 7

Membrane receptors: peptides & catecholamines

Nuclear receptors: Vit D, steroids, TH

Question 8

Negative v. positive feedback

Answer 8

Negative feedback: more common

• when hormone levels are high, further secreiton is inhibited
• when hormone levels are too low, secretion of the hormone is stimulated i.e. testosterone, insulin

Positive feedback: one hormone turns on another hormone i.e. during menstrual cycle – estrogen acts on the anterior pituitary to produce a rapid burst of FSH and LH secretion –> stimulates estrogen secrtion

Question 9

When in the day is cortsiol highest? When is it lowest?

Answer 9

Highest at 8am: if it’s not high at 8am, suspect insufficiency

Lowest at midnight: if it’s not low at midnight, suspect cushing’s

Question 10

Endocrine disorders

Answer 10

Excess

Deficiency

Resistance