Thyroid Physiology Flashcards
What is released in the posterior pituitary?
oxytocin and vasopressin
Which hormones regulate calcium level in the blood?
PTH
caltitonin
calcitriol
What is an example of type II hypersensitivity
Graves (MG is another)
What is the speed and duration of action of a hormone
slow speed, but long duration
T/F endocrine glands usually produce one type of horone
False, glands may produce multiple hormones
What’s involved in Addison’s disease?
chronic adrenal insufficiency (hypo-corticolism)
what’s a neurocrine molecule?
hormone secretion from a nerve signal
what are the three major pathways that use neurocrine signal?
hypothalamus to anterior pituitary
hypothalamus to posterior pituitary
catecholamines form adrenal medulla
what’s a tropic hormone?
a hormone that controls the secretion of another hormone
is tropic hormone different to trophic hormone?
Yes, trophic hormone is one that’s involved in growth and development
Peptide hormone is synthesised in _________, and stored in _______. It requires ________ release because of its ________ nature. Peptides dissolve in the plasma, hence have a ______ half-life. The receptors for peptide are located on the __________, and it will activate second messenger pathway to _________ proteins. An example of peptide hormone is ___________
advance secretory vesicles exocytosis hydrophilic short cell membrane modify existing insulin
Steroid hormone is synthesised __________. It is ________, so does not require vesicles. In the blood, it is bound to _______ and thus have a ______ half-life. Steroid acts on the _______ to modify ________, and usually leads to _______ of new _______. Some examples of steroid hormone are _____, ______, and ________
on demand hydrophobic carrier proteins long nucleus gene transcription synthesis proteins oestrogen, androgen, cortisol
T/F Catacholamines are hydrophobic
False, it is hydrophilic and requires transport vesicle
T/F Catacholamines have short half-life
True
T/F Catacholamines induce synthesis of new proteins
False, it modifies existing proteins
How do protein carriers extend the half-life of hormones?
binding prevents liver metabolism and kidney excretion
Which two locations in the brain are responsible for Circadian rhythms
Pineal gland
Suprachiasmatic nucleus
What is primary endocrine disorder?
when the gland is abnormal
What is secondary endocrine disorder?
when the gland is normal, but the excretion rate is abnormal
Where is the abnormality in Cushing’s
Usually due to hypersecretion of ACTH from the pituitary
CRH from hypothalamus in this case is inhibited
T/F There is a neural link between the hypothalamus and the anterior pituitary
false, there is a vascular link
What is the advantage of having hypothalamic-hypophyseal system over directly releasing hormones into circulation
1) less hormone needs to be secreted
2) tropic hormones can be transported directly to pituitary
Is posterior pituitary a neural tissue?
Yes, it is an outgrowth of nervous tissue with a neural link to the hypothalamus
What’s another name for anterior pituitary?
adenohypophysis
What is the embryologic origin of anterior pituitary
glandular epithelial tissue, ectodermal cells
How to we access the pituitary?
Through the roof of the nasal cavity
What is the stalk connecting hypothalamus to the pituitary
infundibulum
Which bone protects the pituitary?
sphenoid bone
What is the action of vasopressin?
increase collecting duct permeability
decrease urine volume
What is the function of oxytocin?
milk ejection (not production) uterus contraction
what’s the function of prolactin?
milk production
What’s the stimulus for release of oxytoxin?
baby suckle
positive feedback from uterus contraction
T/F oxytocin and vasopressin are formed in the posterior pituitary
False, they are formed in the hypothalamus and transported down
Which two regions of the brain have control of posterior pituitary?
supraoptic and paraventricular nuclei
Which is the hypothalamic-hypophyseal portal system?
between the hypothalamus and the anterior pituitary
what does the HHP system carry?
preformed tropic hormone to the anterior pituitary
T/F HHPS is connected to water circulation
False, it’s a direct delivery system over a short distance
What’s the role of releasing hormones in the hypothalamus?
Stimulate the release of pituitary hormones in response to a positive feedback signal
What’s the role of inhibiting hormones in the hypothalamus
inhibit the release of pituitary hormone in response of a negative feedback signal
T/F the signal to the final production organ provides the negative feedback signal to hypothalamus and pituitary
False, it’s the release of hormones that provide the negative feedback
What the other name for growth hormone?
somatotropin
Does somatotropin have metabolic actions?
Yes, there are metabolic actions in organs such as liver, skeletal muscles and thyroid
What are some higher centre stimuli that can alter hypothalamic secretion
stress, special senses (vision, for example), chemical exposure
What’s the pathophysiology of Kallmann syndrome?
genetic abnormality causing failure of GnRH neurons to migrate to hypothalamus, causing hypogonadism and anosmia
How long does postnatal growth spurt last?
2 years, then growth seems to plateau out with no sex differences
What is “catch up growth”
Compensatory growth between 2 years to adolescent if the growth inhibiting factor is removed
Which tissue has the fastest spur of growth up to about 12 years of age
lymphoid tissue
What’s the other name for insulin like growth factor?
Somatomedin
What’s the metabolic effect of somatotropin
anti-insulin, increase blood fatty acid and glucose during fasting
Promote protein synthesis in muscles
T/F growth hormone is a peptide hormone
True, hence with short half life as it’s not bound by carrier proteins
T/F Growth hormone and thyroid hormone work together for growth
True, thyroid hormone is permissive to growth
Which hormone is our final height determined by
oestrogen
What are some ways that can cause growth hormone deficiency?
Primary disorder in hypothalamus or pituitary
Growth hormone insensitivity (Laron dwardism)
What’s the treatment for GH deficiency?
GH replacement - use genetically engineered human GH
What’s cretinism and what is it caused by?
severely stunted growth due to childhood hypothyroidism
What’s the commonest form of dwarfism in humans?
achondroplasia
What is acromegaly caused by?
excess growth hormones
What does the thyroid gland secret?
thyroid hormone and calcitonin
What is the cellular set up of the thyroid gland?
follicular cells surround the colloid follicle
C cells to produce calcitonin
How much T3 is derived from T4? Which enzyme converts T4 to T3
80%
deiodinase
What are the actions of thyroid hormone?
increased BMR and oxygen consumption
modulate metabolism
SNS mimetic
T/F Stress decreases TRH production
true
When will the production of TRH increase in infants?
in response to cold
Do we get goitre in a hypothalamic failure?
reduced production of TRH and TSH, so no goitre
Why do we get goitre in Graves
TSI acts as a trophic factor to cause goitre
