Thyroid Disease Flashcards
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
what are the signs and symptoms of hyperthyroidism
anxiety and irritability sweating and heat intolerance tachycardia weight loss despite good apetite fatigue frequent loose stools sexual dysfunction eyelid retraction goitre
risks and treatment of thyroid eye disease
intraocular pressure leading to optic nerve damage, corneal ulceration
treatments: steroids, immunosuppression, surgical decompression, radiotherapy
CV effects of hyperthyroidism
higher pulse, BP
AF
investigations of hyperthyroidism
free T4 and TT3 raised, suppressed TSH
what is the first line management of graves; hyperthyroidism
CARBIMAZOLE:
treats patients with graves in 4-8 weeks
continue on maintenance carbimazole and either titration block or block and replace
complete remission usually within 18 months of treatment
side effects: neutropenia and agranulocytosis: see dr if sore throat
what is the second line drug for hyperthyroidism
propylthiouracil
3x daily doses
remission less than carbimazole
side effects: rash, itching, nausea, agranuloyctosis, leukopenia
what other treatments are there for hyperthyroidism
radioactive iodine:
beta and gamma emitter
drinking a single dose
taken up by thyroid gland and emitted radiation destroys proportion of thyroid cells
decrease of TH production
Remission can take 6 months = patients can be left hypothyroid and require levo
•Damages follicular cells
•As time increases, incidence of hypo after therapy increases to upto 80%
how are beta blockers used in hyperthyroidism
blocks adrenalin related symptoms of hyper
propanolol: non-selectively blocks adrenergic activity as opposed to more selective ones that only work on the heart
surgery for hyperthyroidism
remove whole thyroid or toxic nodules
effectively stops production of thyroid hormone, but will require levo
near-total thyroidectomy is standard
take T4 post op
what is neonatal hyperthyroidism
thyroid stimulating antibodies in grave’s disease can cross the placenta and stimulate thyroid gland of fetus
what is post-partum thyroiditis
inflamed thyroid within first year of child birth, can last weeks to months
1/3 of women develop permanent hypothyroidism
what are the signs and symptoms of post partum thyroiditis
personal history of T1DM, tremor, tachycardia, warm moist skin, muscle weakness, lid retraction, lid lag
what would you see on investigations for PPT
fT4 increased to a greater degree than fT3, and also will see TPO autoantibodies
reduced iodine uptake on radioactive scan
what is a goitre
an enlarged thyroid
how do you assess a goitre
toxic, hypo, euthyroid, is it multinodular, or diffuse, are there compression symptoms
clinical signs to differentiate for thyroid cancer
age, duration, iodine status, radiation exposure
thyroid status, presence of solitary nodule v goitre,
multi-nodular disease
pressure symptoms, mobility, skin tethering, lymphadenopathy, RLN palsy
what are the investigations for thyroid nodules
frequent benign disease but low risk of malignancy
USS
fine needle aspiration and cytology (before bloods is a lump is palpable and visible)
what are the main kind of thyroid cancers
papillary carcinoma - 70% derived from follicular epithelium, good prognosis
follicular carcinoma -2 20%
anaplastic and medullary cell carcinoma - arising from c-cells
how is thyroid cancer treated
surgery and post-op radioactive treatment or TSH suppression so tumour growth is not stimulated
pregnancy and hyperthyroidism
grave’s: untreated can lead to difficulties conceiving
if conceiving: change from CMZ to PTU asap
do NOT use block and replace
pregnancy and hypothyroidism
also more diff to concieve if untreated
higher doses of levo during pregnancy; increase by 25mcg so baby gets enough thyroid hormones
UK = babies have heel prick to test for hypo
how else do you test pituitary gland function
TFT's, free T4 LH, FSH, oestradiol, testosterone prolactin cortisol as a measure of ACTH IGF-1 as a measure of GH
what is sheehan’s syndrome
condition that causes ischaemic necrosis to pituitary gland of woman, following hypovolemic shock or severe blood loss during or after childbirth
causes HYPOTHYROIDISM
what are the symptoms of sheehan’s syndrome
inability to breastfeed infrequent menstruation inability to regrow shaved pubic hair hypothyroidism low blood pressure and sugar irregular heart beat
• May not have symptoms for many months or years, but trigger such as severe surgery, which triggers adrenal crisis and hence shows up because adrenal glands don’t produce enough cortisol
what is the treatment for sheehans
HRT
