Pituitary Hormones 1 and 2 Flashcards
What hormones are produced in the posterior pituitary?
AVP and Oxytocin
What are the hormones that are producd in the anterior pituitary?
ACTH
GH
PRL
TSH
FSH
LH
Describe the signalling to the pituitary gland?
neurons in the supraoptic and paraventricular nuclei in the hypothalamus receive signals and control release of hormones from the pituitary *hypophyseal portal system*
How does the thyroid influence pituitary action?
- Hypothalamus releases TRH
- Pituitary gland releases TSH
- TSH stimulates thyroid gland to make Thyroxine
- negative feedback on hypothalamus and pituitary gland
what would grave’s disease look like on a technetium scan?
smooth uptake of entire gland
- note that if it was unilobular, then only asmall part of the thyroid gland would uptake
what occurs in hypothyroidism?
hypothyroidism - thyroid gland doens’t make enough thyroxine to produce negative feedback on pituitary gland and hypothalamus
what are some clinical findings of hypothyroidism?
weight gain
cold intolerance
dry skin, hair
memory loss
constipation
slow pulse
outer one third of eyebrows lost
what is the treatment for hypothyroidism?
give low dose thyroxine (don’t want to increase thyroxine levels too fast or they’ll end up with hyperthyroidism)
- aim to normalise TSH levels -
if heart disease use extra low dose initially and titre slowly -
*there shouldn’t be side effects of thyroxine unless you’re giving too much - in which case you run the risk of causing Afib
what is the connection between the hypothalamus and the testes?
hypothalamus releases GnRH and this stimulates the pituitary to release FSH (sperm production) LH (testosterone production)
- this goes to the testes for their respective functions
- negative feedback, testosterone is a negative feedback to the hypothalamus
what would you expect to find if testosterone levels are very low?
negative feedback on they hypothalamus is removed, therefore you get higher levels of GnRH
what is the diagnosis if you have low testosterone and normal FSH/LH levels?
secondary testicular failure due to pituitary disease/tumour - if it was a primary testicular failure then we would see low testosterone and really high FSH/LH levels
How is the pituitary gland connected to the ovaries?
hypothalamus produces GnRH to pituitary
pituitary producse FSH and LH
FSH -ovulation of ovaries
LH - produces estrogen in ovaries
*estrogen negative feedback on hypothalamus production of GnRH
what occurs to your hormone levels during menopause?
estrogen levels drop due to ovarian failure
removes negative feedback from estrogen
increased levels of FSH and LH
What is the diagnosis if low estrogen, and really high FSH and LH?
menopause
what is the diagnosis of low estrogen level and low FSH and LH?
anorexia, extreme exercise, pituitary tumour
describe the hypothalamo-pituitary adrenal axis
- hypothalamus produces CRF
- stimulates pituitary to produce ACTH
- ACTH stimulates adrenal gland to produce cortisol
- cortisol has negative feedback on the hypothalamus and the pituitary gland
what is the pre-hormone to ACTH?
pro-opiomelanocortin
*also prehorone for Beta-endorphin and melanocyte stimulating hormone
what are the metabolic effects of cortisol
- negative effects bone
- inhibits growth
- effects mood - depression/psychosis
- increase cardiac output
- increase renal blood flow/glomerular filtration rate
- can cause cataracts
- modulate WBC function
what are the consequences of the ACTH excess?
results in cortisol excess
hyperpigmentation
euphoria/psychosis
What is Cushing’s syndrome?
cortisol excess resulting in
- hyperglycameia
- obesity
- muscle weakness
- osteoprosis
- hypertension
- irregular periods
- psychosis
what can you use to induce production of GHRH?
hypoglycaemia, glucagon, arginine, stress, sleep
Describe the growth hormone axis
- hypothalamus produces GHRH
- pituitary gland secretes GH
- GH works on liver to release IGF1- negative feedback on hypothalamus
are growth hormone measurements reliable?
single measurements are not - they raise and drop quite randomly throughout the day - hterefore we use IGF1 most of hte time
what are the effects of Growth hormone?
- linear growth
- glucose metabolism (hyperglycaema)
- lipolysis
- protein synthesis
- renal salt and water reabsorption
what are some clinical features of acromegally? What is the cause?
acromegally - usually a tumour of pituitary - causes too much GH
- produces alarming skeletal growth especially during growth phase of life - if you develop this after your grwoth plates have closed it can still make your bones thicker
- see patients with large hands, prominent chins, larger tongue, larger feet etc.
treatment for this is to remove the tumour
growth hormone deficiency can lead to what?
short stature -
in adults, growth hormone deficiency can lead to poor muscle funciton, fat excess, osteoporosis, cardiac disease and poor quality of life
Describe the hormone system that produces prolactin
- hypothalamus produces Thyrotropin Releasing Factor
- pituitary gland produces prolactin
- prolactin induces breast milk production - and lowers FSH/LH levels = low libido and anovulation
what has a positive feedback on prolactin relases?
the suckling reflex has a positive feedback on the production of prolactin
what is the diagnosis of a woman, 2 years amenorrhoea, low libido, galactorrhoea (milk production)
bloods show very high prolactin
low estradiol
low FSH and LH
pituitary tumour
