thyroid Flashcards
what two main classes of hormones does the thyroid release?
T3 and T4 thyroid hormones
calcitonin
what kind of feedback do T3 and T4 hormones induce upon the hypothalamus and pituitary
negative
what is TRH? where is it released from?
thryotropin releasing hormone, hypothalamus
what is TSH? where is it released from?
thyroid stimulating hormone, anterior pituitary
how do thyroid hormones affect the basal metabolic rate
increase
what are thyroid hormones effect with relation to catecholamines?
makes body more sensitive to catecholamines
how does catecholamine sensitivity affect cardiac output ?
increase
what are the three powerful physiological effects of thyroid hormones?
- increased basal metabolic rate
- sensitivity to catecholamines
- important roles in growth and development
where in the follicle does iodination and coupling of thyroglobulin occur?
apical side/ follicle lumen
where in the follicle does processing of thryoglobulin occur ?
intracellular
where are T3 and T4 released from in the follicle?
basolateral side (bloodstream)
how does iodide get into the follicular cell from the bloodstream?
Na/I cotransporter
what kind of receptor is the thyroid hormone receptor?
intracellular
How are T3 and T4 taken up into the cell?
why must they be taken up like this?
need to be taken up by transporter proteins because they are not very lipid soluble
at rest, where can unbound thyroid hormones associate with?
what do they recruit?
response elements (TRE), recruit co-repressors
what is the action of co-repressors?
weaken gene transcription
how does t4 become t3
de-iodination
T3 binding in the nucleus causes recruitment of _______ to form a _______ with the thyroid hormone receptor.
RXR retinoic acid receptor, heterodimer
thyroid recruitment of what can lead to enhanced transcription of target genes?
co-activators
define hypothyroidism
underactive thyroid/ not enough thyroid hormones
what are the major causes of hypothyroidism? (list 4)
iodine deficiency
autoimmunity towards thyroid
congenital defect
inappropriate hormonal regulation
hypersensitivity to cold is a symptom of _____? (hyper or hypo thyroidism)
hypo
weight gain is a symptom of _______. (hypo or hyperthyroidism)
hypo
bradycardia is a symptom of ________. (hypo or hyperthyroidism)
hypo
what are the two types of hypothyroidism? measurement of _______ can help distinguish which one is afflicting a patient.
- primary hypothyroidism
- secondary hypothyroidism
TSH (thyroid-stimulating hormone)
what causes primary hypothyroidism?
DEFECT in thyroid function
what causes secondary hypothyroidism?
central defect ie poor function of anterior pituitary or hypothalamus
what are the features (ie hormone amounts) in someone with primary hypothyroidism?
low T3/ T4
high TSH
what are the features (ie hormone amounts) in someone with secondary hypothyroidism?
low T3/T4, low TSH
what is the most common treatment of hypothyroidism
hormone replacement with synthetic thyroxine (T4)
WHAT IS LEVOTHYROXINE?
what does it treat?
synthetic T4 hormone
treats hypothyroidism
what are the 2 common causes of hyperthyroidism?
Grave’s disease
hyperplasia of the thyroid
what causes Grave’s disease?
stimulatory auto-antibodies that activate the TSH receptor
what is hyperplasia?
enlargement of an organ
what are thyroid adenoma and goitre?
enlargementh of the thyroid gland causing hyperthyroidism
heat intolerance is a symptom of _______ (hyper or hypo thyroidism)
hyper
tachycardia is a symtpom of _________ (hyper or hypo thyroidism)
hyper
tremor is a symptom of (hyper or hypothyroidism)
hyperthyroidism
what is secondary hyperthyroidism ?
central defect in the anterior pituitary, too much TSH release
what are the features (ie hormonal amounts) present in Grave’s disease?
low TSH
high T3, high T4
detection of anti-TSH receptor antibodies
what feature (ie hormonal amounts) is present in thyroid hyperplasia
high T3 and T4
low TSH
what features (ie hormonal amounts) are found in someone with secondary hyperthyroidism?
high TSH
high T3 and T4
what physiological signifier might suggest that someone has high levels of anti-TSH
bulging eyes or exophthalmos
what does Hashimoto’s thyroiditis cause?
hypo or hyper thyroidism
hypo
what is goitre?
what two things may cause goiter?
swelling of the neck
- overactivation of thyroid tissue
- iodine deficiency / increased TSH levels
what does methimazole do?
to what class of drug does it belong?
what is it used to treat?
what are the drawbacks?
prevents steps of T4/T3 synthesis
thioamides
hyperthyroidism
diverse side effects
what is radioactive iodine treatment
what does it treat
what are its drawbacks?
destruction of the thyroid
hyperthyroidism
should not be used in pregnant women because infant can have permanent thyroid damage
how can surgery cure hyperthyroidism?
what are the drawbacks?
resection of part of all of the thyroid + hormone replacement
potential to disrupt parathyroid gland, may cause hypothyroidism
how does treatment with beta-blockers help those with hyperthyroidism?
may help with the tachycardia caused by hyperthyroidism
what is a thioamide? what can it be used to treat
Prevents iodination and coupling steps, used to treat hyperthyroidism
