Thyroid Disease Flashcards
(49 cards)
anatomy of thyroid gland
anterior to trachea, below thyroid cartilage of larynx
what is the histology of the thyroid gland
colloid - resevoir hormone where thyroid hormones are made
columnair epithelium: thyroid follicular cells which make thyroglobulin
interspersed c-cells make: calcitonin
what is hypothyroidism
inadequate output of thyroid hormones by thyroid gland
what are the causes of hypothyroidism
hashimoto’s thyroiditis - auto immune inflammation of thyroid gland, associated with anti-thyroid peroxidase AB and anti-thyroglobulin AB
iodine deficiency
secondary to treatment of hyperthyroidism (carbimazole, PTU, thyroid surgery)
medications:
lithium inhibits production of thyroid hormones
amiodarone can cause thyrotoxicosis
pituitary - secondary hypothyroidism
what are the symptoms and signs of hypothyroidism
weight gain fatigue dry skin coarse hair and hair loss and nail changes cold intolerance fluid retention - oedema, ascites heavy or irregular periods constipation muscle cramps muscle weakness
what are the investigations for hypothyroidism
low free t3 and t4
TSH - high
management of hypothyroidism
oral levothyroxine (synthetic T4), 50-100mg
check T4 levels every 4 weeks and adjut in steps of 25ug
if pregnant; hypothyroid women need to have a higher dose
what are the side effects of levothyroxine
atrial fibrillation and osteoporosis
what is a myxoedema coma
severe hypothyroid state before death
what are the signs and symptoms often >65 years: hypothermia, hyporeflexia, decreased glucose, bradycardia, psychosis, coma, seizures
precipitants: thyroid surgery, radioidone, pituitary surgery.
what is the management of myxoedema coma
bloods for T4, T3, TSG, FBG, U&E, cultures, cortisol, glucose
ABG’s, for PaO2, high-flow o2 if cyanosed, may need ventilation
correct any hypoglycaemia
give liothyronine, 5-20 ug /12 h IV slowly, monitoring for precipitation of ischaemic heart disease
consider levothyroxine
give hydrocortisone 100mg/6h IV
treat suspected infection with co-amoxiclav 1.2g/8h IV
rehydrate with fluids, watching for cardiac dysfunction, inotropes may needed if BP does not respond
active warming if hypothermic
physiology of thyroid hormone synthesis?
HT releases TRH
APG release TSH
thyroig gland releases T4 and T4
iodide attaches to tyrosine (from thyroglobulin) to form MIT or DIT
hence forming either T3 or T4
transport in the blood bound to thyroid-binding globulin
more t4 is secreted but when they arrive at target cells t4 is converted to t3 because it is more active
-READ NOTES ON IPAD FOR MORE DETAIL
how does t3 act on target cells
binds to T3R, nuclear hormone receptor
binds to this, then binds to the DNA, causing gene transcription and producing mRNA
what effects do thyroid hormones produce
growth
increasing metabolic rate
CNS development
metabolism: increases o2 consumption, glc absorption and gluconeogenesis, lipolysis and protein synthesis,
CV: increases cardiac output and respiration
what is hyperthyroidism
overproduction of thyroid hormone by the thyroid gland
what is thyrotoxicosis and how is it different to hyperthyroidism
TTC is characterised by the clinical manifestations of high thyroid hormone ACTION in tissues
what is primary v secondary hyperthyroidism
primary: due to thyroid pathology
secondary: thyroid is producing excessive thyroid hormone as a result of overstimulation by TSH, so pathology is in HT or pituitary
what is grave’s disease
auto-immune condition where TSH receptor antibodies are abnormal, produced by the IS, that mimic TSH and stimulate TSH receptors on the gland causing hyperthyroidism
what are thyroid function tests
free T3, total T3, free T4, TSH
AB: TPO (antibodies against thyroid peroxidase: this is not normally present but if thyroid is destroyed then increased levels)
AB against TSH-R: AB may drive TSH for proliferation and indicates hyperactivity of follicular cells
what are the symptoms specific to grave’s disease
exophthalmos - bulging eyeball
pretibial myxoedema – mucin deposits under skin on front of leg as reaction to the TSH receptor AB
diffuse goitre
nail changes: thyroid acropachy
risk factors for graves disease
age: 40+
family history of any kind of immune disorder, eg coeliac or anything
what is toxic multionodular goitre
cause of hyperthyroidism
nodules developing on the thyroid gland that act independently of the normal feedback system
continously produce excessive thyroid hormone
specific to:
goitre with firm nodules
most patients over 50
what are the other causes of hyperthyroidism
solitary toxic thyroid nodule: single abnormal thyroid nodule acting alone to release thyroid hormone (benign adenomas usually)
thyroiditis: de quervains
viral infection with fever, neck pain, dysphagia
just need NSAID’s and beta blockers
thyroid storm
drugs: amiodarone and interferon
what is a thyroid storm and what are the S&S
thyrotoxic crisis
symptoms: agitation and confusion, coma, tachycardia, diarrhoea and vomiting, goitre, thyroid bruit
causes: recent thyroid surgery, radioiodine, infection, MI, trauma
how do you manage a thyroid storm
IV fluids
bloods for t3,t4, cultures
b blockers: propanolol, or diltiazem
antithyroid drugs: carbimazole, aqueous iodine
steroids: hydrocortisone or dexamethasone to prevent peripheral conversion of T4 to T3
