MedEd Chem 1 Flashcards
describe the endocrine axis in the body
hypothalamus –> pituitary –> end organ
(tertiary) (secondary (primary)
- negative feedback from each to the one above
- external factors control the negative feedback
where is thyroid
inferior to larynx
vascular supply to thyroid
3 arteries (superior, inferior, thyroid ima) and veins (superior, middle, inferior)
2 functions of thyroxine and the R it acts on
acts on intranuclear receptor
regulates BMR
potentiating reponses to catecholamines
describe histology of thyroid gland
stroma (pale) with colloid (pink) surrounded by follicular cells (dark purple) and parafollicular cells between follicular cells
production of thyroxine
stimulated by TSH
thyroglobulin secreted by follicular cells
moved into colloid
oxygenation and iodination of thyroglobulin by thyroid peroxidase
makes t4
moves back into follicular cells
secreted into blood
what is free thyroxine
t4
t4 to t3 by which enzyme
deiodinase enzymes
how many iodine molecules does t4 have
2
what do parafollicular cells secrete
calcitonin
what does calcitonin do
regulates (reduces) calcium
sx of too much thyroxine
tremor
sweating
weight loss
palpitations
heat intolerance
goiter
anxiety
sx of hypothyroidism
weight gain
puffiness
reduced heart rate
constipation
depression
describe period dysfunction in hypo/hyperthyroidism & why
hypo = heavy periods
hyper = oligomenorrhoea with light periods
thyroxine has anti oestrogen effects - too much = blocks ovulation, too little = endometrial proliferation
what actually causes a goitre
high TSH causing proliferation
what types of thyroid issues cause goitre
primary hypothyroidism - TSH produced in response to low t4
secondary / tertiary hyperthyroidism - too much TSH produced
buzzword clinical features of specific thyroid diseases
pretibial myxoedema = graves
exopthalmus = hyperthyroidism (esp graves)
myxoedema coma = hypothyroidism
what scan is done in thyroid disease
radio iodine technetium scan
radio iodine scan of graves
butterfly thyroid - diffuse uptake through whole of thyroid
radio iodine scan of toxic multinodular goitre
discrete patches of uptake where the nodules are
radio iodine scan of toxic adenoma
single very dark spot showing intense uptake in one area over cancer
causes of hyperthyroidism
graves
de quervains
thyroid adenoma / ectopic
drug induced
toxic multinodular goitre
PP
iodine / jon basedow reaction
what is graves
AID hyperthyroidism due to auto ABs to TSH R
reaction to what drug can cause hyperthyroidism
amiodarone