1- basic principles

Question 1

what are the 4 main groups of hormone receptors?

Answer 1

1. G-protein coupled receptors
2. receptor tyrosine kinase (RTK) families
3. cytokine receptors associated with tyrosine kinase activity
4. steroid hormone receptors

Question 2

what is hypothalamic pituitary axis?

Answer 2

system where hypothalamic neurons secrete factors that act on pituitary to release hormones

• there’s also a feedback loop to maintain balance in body

Question 3

what hormones does anterior & posterior pituitary produce?

Answer 3

anterior pituitary releases →ACTH, TSH, LH & FSH, GH, prolactin

posterior pituitary releases →ADH & oxytocin

Question 4

what is thyroid axis?

Answer 4

= regulatory system for thyroid

hypothalamus releases TRH →anterior pituitary releases TSH →thyroid gland releases thyroid hormones

Question 5

what does
a) high TSH
b) low TSH
levels on blood measure mean?

Answer 5

a) high TSH means hypothyroid
b) low TSH means hyperthyroid

Question 6

what is negative feedback loop for thyroid axis?

Answer 6

thyroid produces hormones in response to TSH, if enough thyroid hormones in blood, signal sent back to hypothalamus & pituitary to reduce TRH & TSH

Question 7

what might make TSH test not reliable marker for thyroid status?

Answer 7

feedback loop needs to be working for TSH test to be reliable (as if no feedback mechanism then TSH levels won’t represent thyroid hormones) so if pituitary dysfunction then not reliable test

Question 8

what is hypothalamic pituitary adrenal axis?

Answer 8

hypothalamus secretes CRH (corticotropin releasing hormone) →anterior pituitary releases ACTH (adrenocorticotropic hormone) →adrenal cortex (outer layer of adrenal gland) releases cortisol

Question 9

what is circadian cortisol secretion?

Answer 9

waking up = gradual rise in cortisol from 5am-9am peak

• decreases throughout day so lowest at midnight

Question 10

what is growth hormone axis?

Answer 10

they’re released in pulsatile spikes (at random) so only growth hormone to measure is IGF1 as stable throughout day

Question 11

what are 2 main functions of sex hormones?

Answer 11

1. regulate production of steroid hormone (oestrogen or testeroste)
2. regulate fertility

Question 12

what is prolactin? where?

Answer 12

= hormone mostly known for role in lactation, pregnancy

• secreted by lactotroph cells in anterior pituitary
• prolactin makes effects by binding to prolactin receptor (PRLR)

Question 13

what is feedback loop & control for prolactin?

Answer 13

• controlled by inhibition of hypothalamus, mostly by dopamine causing tonic inhibition (constant suppression)
• secretion is regulated itself by short loop negative feedback, high prolactin feedback to hypothalamus to increase dopamine secretion

Question 14

what are 2 main effects of anti-diuretic hormone?

Answer 14

1. acts to stimulate reabsorption of water from kidneys through aquaporin channels (can do through RAAS)
2. increase blood pressure

= basically it’s 2 main effects are the 2 main effects for RAAS too (increase Na reabsoprtion & K+ excretion and increase BP)

Question 15

generally - if have deficiency of hormone should you test to stimulate or inhibit that hormone?

Answer 15

deficiency of hormone = test to stimulate

*try stimulate hormone, if not enough happens then because not enough of hormone there to be stimulated

Question 16

generally if think have excess of hormone should you test to suppress or stimulate it?

Answer 16

excess of hormone = test to suppress it

*if give suppressor and hormone levels stay high or don’t reduce enough then know excess of hormone