thyroid gland Flashcards
(25 cards)
functions of thyroid hormone
raise metabolic rate
promote thermogenesis
increases hepatic gluconeogenesis
net increase in proteolysis
net increase in lipolysis
critical for growth
essential for brain development in utero
where does the thyroid gland lie vertebral level
C5-T1
what are the thyroid hormones called
triiodothyromine T3
thyroxine T4
what are the two cell types in thyroid gland
C (clear) cells
follicular cells
what do follicular cells do
support thyroid hormone synthesis and surround hollow follicles
make thyroglobulin- rich in tyrosine residues
then into colloid and in colloid, tyrosine residues and iodine combine to form thyroid hormones
how is T3 made
1 iodine + tyrosine makes MIT
2 iodine + tyrosine makes DIT
MIT + DIT = T3
how is T4 made
1 iodine + tyrosine makes MIT
2 iodine + tyrosine makes DIT
DIT +DIT = thyroxine T4
are T 3 and T4 inactive or active
mainly bound to plasma proteins and inactive. they are lipid soluble. only 0.2% are active
there is more of T4 as it has longer half life but T3 binds more to TH receptors so is more active
hyperthyroidism can be caused by
primary-
graves disease
toxic multinodular goitre
toxic adenoma
secondary-
pituitary adenoma
hypothyroidism causes
primary-
congenital
hashimotos thyroiditis- autoimmune
iatrogenic
deficiency in dietary iodine
pst subacute thyroiditis
secondary-
pituitary adenoma
craniopharyngioma
post pituitary surgery or radiotherapy
subclinical- risk of overtreating, normal T3 and T4 but abnormal TSH
hypothyroidism signs and symptoms
weight gain
lethargy
feeling cold
constipation
heavy periods
dry skin/hair
bradycardia
slow reflexes
goitre
severe- puffy face, large tongue, hoarseness, coma
hyperthyroidism signs and symptoms
weight loss
anxiety/irritability
heat intolerance
bowel frequency
light periods
sweaty palms
palpitations
hyperreflexia/tremors
goitre
thyroid eye symptoms/signs
tests for hypothyroidism
TFTs- TSH and T4
FBC
glucose and HbA1C
management for hypothyroidism
levothyroxine - first thing in morning empty stomach
measure TFTs every month until TSH level stabilises then once a year
hypothyroidism in pregnancy managment
empirical dose
regular monitoring
aim for TSH lower half of normal
post natal reduce levothyroxine to prepregnancy dose 2 weeks after
recheck 2-3 months post pregnancy
management for hyperthyroidism
antithyroid drugs - carbimazole or propylthiouracil 1
radioiodine 2
surgery 3
subclinical hyperthyroidism
normal T3 and T4
TSH suppressed
risk of bone density decreases
AF risk
single nodular thyroid test
US first line
FNA if suspicious
risk of malignancy if a child, previous H+N radiation, pain
TFTs
thyroid cancer types
papillary, lymphoma, anaplastic, medullary and follicular
papillary thyroid cancer
commonest
multifocal
good prognosis
follicular thyroid cancer
usually single lesion
metastases to lung and bone
good prognosis if resectable
poorer if <16yo or >55yo
management thyroid cancer
near total thyroidectomy
high dose radioiodine
thyroxine long term
follow up- whole body iodine scanning following 2- 4 weeks of thyroxine withdrawal
biopsy
thyroiditis causes
inflammation of thyroid gland
autoimmune disorders
viral infections
radiation therapy
graves disease
autoimmune disease
F>M
TSH receptor antibodies
between 20 and 40
bulging eyes (exopthalmus) or eye irritation
causes hyperthyroidism
