intro to endocrnology Flashcards
major components of endocrine system
- pituitary
- thyroid
- parathyroid
- adrenal
-pancreas - ovary
- testes
define endocrinology
the study of hormones (and their gland of origin), their receptors, the intracellular signalling pathways, and their associated diseases
define endocrine
glands pour secretions into blood stream
define exocrine
outside
glands pour secretions through a duct to site of action
examples of endocrine glands
thyroid, adrenal, beta cells of pancreas
examples of exocrine
pancreas - amylase, lipase
2 categories of hormones
water soluble
fat soluble
compare transport of water soluble and fat soluble hormones
water soluble - unbound
fat soluble - protein bound
compare cell interaction in water soluble and fat soluble
water soluble - bind to surface receptor
fat soluble - diffuse into cell
compare half life of water soluble and fat soluble hormones
water soluble - short
fat soluble - long
compare clearance of water soluble and fat soluble hormones
water soluble - fast
fat soluble - slow
2 examples of water soluble hormones
peptides, monoamines
2 examples of fat soluble hormones
thyroid hormone, steroids
describe endocrine hormone action
blood - borne
acting at distance sites
describe paracrine hormone action
acting on adjacent cells
describe autocrine hormone action
feedback on same cell that secreted hormone
where are peptides and monoamines stored
in vesicles
where are steroids stored
they are not
they are synthesised on demand
describe length of peptide hormones
they vary in length
TRH- 3 amino acids
gonadotropins - 180 amino acids
describe structure of peptide hormones
liner or ring structure
two chains and may bind to carbohydrates eg LH,FSH
characteristics of peptide hormones
stored in secretory granules
hydrophilic
water soluble
how are peptide hormones released
in pulses or bursts
how are peptide hormones cleared
by tissue or circulating enzymes
describe process of making peptide hormones
- synthesis : preporhormone -> prohormone
- packaging: prohormone -> hormone
- storage: hormone
- secretion: hormone
what do peptide hormones do
act as surface receptor and secondary messenger activation
what are all amines derivatives of
phenylanine
what are amines secreted by
medulla
what is the rate limiting step in amine production
the conversion to L-DOPA
what does cortisol do in amine production
cortisol potentiates conversion of norepin to epin
characteristics of amines
- water soluble
- stored in secretory granules
- release pulsatile
- rapid clearance e
which receptors to amines bind
bind to alpha and beta receptors or D1 and D2
impact of alpha receptors
vasoconstrition
dilated pupil
alertness
contraction of stomach bowel, anal sphincter
what happens when adrenoreceptors become activated
stimulates the sympathetic nervous system - fight or flight response
are thyroid hormones wate soluble
no
99% is protein bound
how much of T3 in blood is secreted directly by thyroid
only 20% of T3 in the circulation is secreted directly by thyroid
process of thyroid release
- secretory cels release thyroglobulin intro colloid - acts as base for thyroid hormone synthesis
- incorporation of iodine on tyrosine molecules to form iodothyrosinases
- conjugation of iodothyrosines gives rise to T3 and T4 and stored in colloid bound to thyroglobulin
- TSH stimulates the movement of colloid into secretory cell, T4 and T3 cleaved from thyroglobulin
3 locations of hormone receptors
- cell membrane - peptide
- cytoplasm - steroid
- nucleus - thyroid
what’s in the nuclear receptor family
- oestrogen
- thyroid hormone
- vit D
what’s in the steroid receptor family
- glucocorticoids - cortisol
- mineralcorticoids - aldosterone
- androgens - testosterone
- progesterone
give an advantage of cell membrane receptors
cell selectivity
which receptor sites may alter cell transcription
all 3 receptor sites - cell membrane, cytoplasm, nucleus
which type of hormone are more lipid soliuble
steroids
they are more lipid soluble to cross cell membrane
describe solubility of vitamin D
fat soluble
how does vitamin D enter cells
enters cells directly to nucleus to stimulate mRNA production
how is vitamin D transported
by vitamin D binding protein
how much of adrenocortical and gonadal steroids are protein bound
95%
what happens to adrenocortical and gonadal steroids after entering cell
- pass to nucleus to induce response
- altered to active metabolite
- bind to a cytoplasmic receptor
describe inactivation of adrenocortical and gonadal steroids
not too rapid
in liver by reduction and oxidation
or
conjugation to glucoronide and sulphate groups
describe the intracellular steroid pathway
- steroid hormone diffuses through plasma membrane and binds to receptor
- receptor hormone complex enters nucleus
- receptor hormone complex binds to GRE
- binding initiates transcription of gene to mRNA
- mRNA directs protein synthesis
how is hormone secretion controlled
- basal secretion - continuously or pulsatile
- superadded rhythms - eg day nighy cycle
- release inhibiting factors
- releasing factors
how is hormone action controlled
- hormone metabolism
- hormone receptor induction
- hormone receptor down regulation
- synergism
- antagonism
how does hormone metabolism control hormone action
increased metabolism to reduce function
how does hormone receptor induction control hormone action
induction of LH receptors by FSH in follicle
how does hormone receptor down regulation control hormone action
hormone secreted in large quantities cause down regulation of its target receptors
how does synergism affect control of hormone action
combined effects of two hormones amplified
eg glucagon with epinephrine
how does antagonism control hormone action
one hormone opposes other hormone
eg glucagon antagonises insulin
describe negative feedback
initial stimulus
response
decreased stimulus
response loop shuts off
describe positive feedback
initial stimulus
response
increased stimulus
back to response
how do you shut positive feedback
an outside factor is required
3 types of negative feedback loops
short loop negative feedback
ultra short loop negative feedback
long loop negative feedback
what components are shown in MRI of normal pituitary gland
optic chiasm
hypothalamus
pituitary stalk
which cranial nerves are around pituitary gland
oculomotor
trochlear
abducens
ophthalmic
maxillary
what does the posterior pituitary gland produce
- hypothalamic neurones synthesis oxytocin or ADH
- oxytocin and ADH are transported down the axons of the hypothalamic - hyphophyseal tract to the posterior pituitary
- oxytocin and ADH are stored in axon terminals in posterior pituitary
- when hypothalamic neurones activated , hormones released
what does oxytocin do
stimulates mammary glands and labour conyraction
what hormones are secreted by anterior pituitary gland
TSH - thyroid
ACTH -adrenal cortex
FSH & LH - testes or ovaries
GH - entire body
Prolactin PRL - mammary glands
what happens if you get pituitary dysfunction
tumour mass effects
hormone excess
hormone deficiency
investigations for pituitary dysfunction
hormonal tests
if hormonal tests are abnormal or tumour mass effects perform MRI pituitary
describe the hypothalamo - pituitary - thyroid axis
hypothalamus -> anterior pituitary -> thyroid gland
describe thyroid hormone function
Accelerates food metabolism
Increases protein synthesis
Stimulation of carbohydrate metabolism
Enhances fat metabolism
Increase in ventilation rate
Increase in cardiac output and heart rate
Brain development during foetal life and postnatal development
Growth rate accelerated
describe hypothalamo - pituitary - adrenal axis and cortisol actions
hypothalamus -> anterior pituitary -> adrenal cortex
hormones :
CRH -> ACTH -> CORT
components of adrenal gland
capsule
zona glomerulosa
zona fasciculata
zona reticularis
adrenal medulla
3 types of steroids
mineralocorticoids - aldosterone
glucocorticoids - cortisol androgens
androgens - androstenedione, DHEA
primary regulators of RAAS system
decrease in blood volume and/or blood pressure
increase in K+ in loop
impact of RAAS system
increased absorption of Na+ and water
increased K+ excretion
increased blood volume and/or blood pressure
describe adrenal hormone short term stress response
- heart rare increases
- blood pressure increases
- bronchioles dilate
- liver coverts glycogen to glucose and releases glucose to blood
- blood flow changes, reducing digestive system activity and urine output
- metabolic rate increases
long term stress response from adrenal horm,one
- kidneys retain sodium and water
- blood volume and bp rise
- proteins and fats converted to glucose or broken down for energy
- blood glucose increases
- immune system suppressed
where is FSH produced
granulosa cell
where is LH produced
theca cell
describe formation of eostgroen
cholesterol -> androgen -> oestrogen
via enzyme aromatise
5 steroid actions
- Steroid hormone diffuse through plasma membrane and binds to receptor
- Receptor-hormone complex enters nucleus
- Receptor-hormone complex binds to GRE
- Binding initiates transcription of gene to mRNA
- mRNA directs protein synthesis
what does the adrenal cortex produce
Produces steroids hormones:
Mineralocorticoids e.g. aldosterone
Glucocorticoids e.g. cortisol androgens
Androgens e.g. androstenedione and DHEA
what does the adrenal medulla produce
Produces epinephrine and norephinephrine
