Physiology - Thyroid Flashcards
thyroid gland tissue secretes what?
thyroxine (T4)
tri-iodothyronine (T3)
calcitonin
the 4 parathyroid glands secrete what?
parathyroid hormone (PTH)
the thyroid is situated between the _th cervical and _st thoracic vertebrae
the thyroid is situated between the 5th cervical and 1st thoracic vertebrae
what is sometimes absent from the thyroid?
isthmus
thyroid innervation:
sympathetic -
parasympathetic -
sympathetic - sup. inf. and middle ganglia of sympathetic trunk
parasympathetic - vagus (CN X)
thyroid blood supply?
superior and inferior thyroid arteries
nexus drainage of thyroid?
3 pairs:
superior/middle thyroid vein
what is the other name for the posterior suspensory ligament?
berry ligament
what nerve is at risk of damage in surgery of the thyroid?
recurrent laryngeal nerve
the colloid contains ________ enclosed by __________ cells
the colloid contains TYROSINE enclosed by FOLLICULAR cells
what do parafollicular C cells secrete?
calcitonin
what element is used to synthesise thyroid hormone?
iodine
thyroxine hormone has how many iodines attached to it?
4
what drug is used to prevent active hormone being produced?
carbimazole
- iodine taken up by ________ cells
- _______ attached to tyrosine residues on thyroglobulin to form MIT and DIT
- coupling of MIT and DIT (T_) and 2 DITs (T_)
- stored in colloid thyroglobulin till required
- iodine taken up by FOLLICLE cells
- IODINE attached to tyrosine residues on thyroglobulin to form MIT and DIT
- coupling of MIT and DIT (T3) and 2 DITs (T4)
- stored in colloid thyroglobulin till required
T3 or T4?
90% of secreted thyroid hormone
10% of secreted thyroid hormone
T_ is 4 times more potent than T_
T_ is converted to T_ in any cell
major biologically active thyroid hormone
90% of secreted thyroid hormone -T4
10% of secreted thyroid hormone - T3
T3 is 4 times more potent than T4
T4 is converted to T3 in any cell
major biologically active thyroid hormone - T3
T3 and T4 are _____phobic so bind to plasma proteins
T3 and T4 are HYDROPHOBIC so bind to plasma proteins
name the 3 major binding protein that T3 and T4 bind to
thyroxine binding globulin - TBG
thyroxine binding prealbumin - TBPA
albumin
bound or unbind is the biologically active form?
unbound
only the ________ hormone is available to tissue
only the UNBOUND hormone is available to tissue
what increases the total binding globulin but has no effect on free?
pregnancy
name the effects of thyroxine
moist skin anxiety tachycardia palpitations loose bowels lose period muscle wasting
what hormones increase basal metabolic rate, thermogenesis, carbohydrate, lipid and protein metabolism
thyroid hormones
you need thyroid hormone for ____ production and so for growth
you need thyroid hormone for GHRH production and so for growth
what drug is used to treat sympathetic symptoms in initial stages of hyperthyroidism?
propanolol
___ from hypothalamus stimulates ___ release from _________ pituitary
TSH is the major stimulant to release T3 and T4 from the ________ gland
T3 and T4 exert ________ feedback control of TRH and TSH release
TRH from hypothalamus stimulates TSH release from ANTERIOR pituitary
TSH is the major stimulant to release T3 and T4 from the THYROID gland
T3 and T4 exert NEGATIVE feedback control of TRH and TSH release
in babies:
cold stimulates ___ release
which stimulates ___ release
so increases __ and __ release from thyroid
in babies:
cold stimulates TRH release
which stimulates TSH release
so increases T3 and T4 release from thyroid
what inhibits TRH and TSH release?
stress
thyroid hormone is highest at _____ and lost in the ________
thyroid hormone is highest at NIGHT and lost in the MORNING
name the important family of enzymes important in the activation an deactivation of thyroid hormone
name the particularly important member of this family
delodinase enzymes
Type 3
__ activates T4 to T3 in tissues
D2 activates T4 to T3 in tissues
name the location of the following de-iodinase enzymes:
type I -
type II -
type III -
type I - liver and kidney
type II - heart, muscle, CNS, fat, thyroid, pituitary
type III - fetal tissue, placenta and brain - NOT pituitary
primary thyroid gland failure may result in the presentation of what?
a goitre (enlarged thyroid)
goitre or no goitre:
secondary to TRH or TSH
no goitre
goitre or no goitre:
lack of iodine in diet
may be associated with goitre
hypothyroidism symptoms?
reduced BMR slow pulse rate fatigue, lethargy, mental sluggishness cold-intolerance put on weight
name the condition in adults associated with puffy face, hands and feet
myxoedema
name the condition in babies associated with dwarfism and limited mental functioning due to deficiency of thyroid hormones at birth
cretinism
name the common disease associated with hyperthyroidism
grave’s disease
is graves disease autoimmune?
yes
what is bulging of the eyes called in graves disease called?
exophthalmos
is there a goitre in graves disease?
yes
graves disease symptoms?
increased BMR fast pulse increased nervousness insomnia sweating heat intolerance lose weight
what is the main regulator of thyroid hormone release?
TSH
what is the most biologically thyroid active hormone?
T3
