Thyroid Flashcards
What are the physiological effects of thyroid hormones?
- increase O2 consumption & glucose absorption
- increase HR, excitability & conductivity
- increase skeletal & sexual maturation
- decreases serum cholesterol level
What affects total T3 & T4 measurements
Thyroxin binding globulin (TBG)
- total T4 = 4 - 12
- total T3 = 80 - 120
increase TBG -> pregnancy, estrogen, congenital
decrease TBG -> liver cell failure, nephrotic syndrome, malnutrition, congenital, androgens
Radio-active iodine uptake (RAIU) is useful in diagnosis of?
Hyperthyroidism
except in cases of -> thyrotoxicosis factitia
-> thyroiditis
-> ectopic thyroid tissue (struma ovarii)
What is the most sensitive test for differentiation between primary & secondary thyroid dysfunction?
Serum TSH
PRIMARY
hyperthyroidism -> increase T3 & T4 + decreased TSH
hypothyroidism -> decreased T3 & T4 + increased TSH
SECONDARY
hyperthyroidism -> increased T3 & T4 & TSH
hypothyroidism -> decreased T3 & T4 & TSH
What are the anti-thyroid antibodies that could be found?
- Thyroid stimulating immunoglobulin (TSI or LATS) -> Graves’ disease
- Anti-microsomal & antithyroglobulin -> Hashimoto’s thyroiditis
- TSH binding inhibitory immunoglobulin (TBII) -> primary hypothyroidism
- serum thyroglobulin -> increases in differentiated cancer thyroid
What is the significance of thyroid scanning using 99mTC?
- defines areas of hot nodules or cold nodules
- retrosternal goiter
- ectopic thyroid tissue
- functioning metastasis of thyroid carcinoma
What are the causes of thyrotoxicosis?
THYROID HYPERFUNCTION
- Graves disease (Basedow disease)
- toxic nodule
- toxic adenoma
- iodine induced hyperthyroidism
- TSH-secreting pituitary tumor
- choriocarcinoma
ABNORMAL THYROID HORMONE RELEASE
- subacute thyroiditis
- chronic thyroiditis with transient thyrotoxicosis (Hashitoxicosis)
- Hamburger thyroiditis
EXTRA-THYROID TISSUE
- Thyrotoxicosis factitia
- ectopic thyroid tissue -> Struma ovarii or functioning metastatic follicular carcinoma
What is the cause of Grave’s disease?
- auto-antibody belonging to IGg class -> TSI or LATS (thyroid stimulating immunoglobulin)
- can lead to transient neonatal thyroiditis because antibodies can cross the placenta
What are the general manifestations of Grave’s disease?
- progressive weight loss + increasing appetite -> hyperdefecation due to increase GIT motility
- heat intolerance
- increased sweating
- nervousness, emotional liability
- irritable, agitated
- exaggerated reflexes
- fine tremors
What are the cardiovascular manifestations of Graves disease?
- all types of arrhythmias EXCEPT heart block
- high cardiac output failure -> water-hammer pulse
- flow murmur -> hyper dynamic circulation
- increase systolic hypertension -> increase pulse pressure
What are the musculoskeletal manifestations of Grave’s disease?
- Myopathy, Myasthenia Graves
- bone resorption -> hypercalcuria & hypercalcemia + osteoporosis
What are the skin manifestations of Graves disease?
- warm with excessive sweating
- onycholysis -> Plumer nail
- orange peel thickening of pretibial area
- clubbing of fingers & toes -> thyroid acropachy
What are the reproductive manifestations of Graves disease?
- women -> oligomenorrhea & deceased fertility
- men -> impotence, decreased sperm count & gynecomastia
What are the ocular manifestations of Graves disease?
SPASTIC
- Roenbach’s sign -> tremors of closed eyelids
- Stellwag sign -> infrequent blinking
- Dalrymple sign -> starring look
- Von Graefe’s sign -> lid lag
- Joffroy’s sign -> absence of forehead wrinkling
MECHANICAL (infiltrative opthalmopathy)
- proptosis & ophthalmoplegia (diplopia)
- Mobius sign -> lack of convergence
- Conjunctivitis, chemosis, peri-orbital swelling
- corneal ulceration, optic neuritis & optic atrophy
What are the causes of thyroid storm (thyrotoxicosis crises)?
- excessive manipulation of thyroid during thyroidectomy
- neglected severe hyperthyroidism + intercurrent illness
Clinical picture -> severeeee
- tachycardia
- fever
- irritability
- diarrhea
- psychosis
What are the indications of medical treatment of hyperthyroidism?
- thyrotoxicosis in pregnancy
- cases complicated by Heart Failure
- young patients < 25 yo
- pre medication before surgery
What are the contra-indications of medical treatment of hyperthyroidism?
- huge goiter
- retrosternal goiter
- suspicion of malignancy
What are the medications used in hyperthyroidism treatment?
THIONAMIDE -> inhibit thyroid peroxidase
- propyl thiouracil -> in pregnancy -> 300 - 600mg -> decrease peripheral production of T3 from T4
- methimazol -> 30 - 60mg
- carbimazol -> 30 - 60mg -> decreases the production of TSI
give for 6 weeks then follow up -> continue for 1 - 2 years
BETA BLOCKERS -> propranolol (inderal)
- decreases excessive adrenergic activity
- decreases converge of T4 to T3
Na Ipodate -> decreases T4 to T3 convergence
K. iodine -> decrease vascularity of gland
- used to prepare patient for surgery 10 days prior (5 drops)
Dexamethasone -> decreases secretion of thyroid hormone & T4
What are the side effects of thionamide drugs?
- agranulocytosis
- arthralgia
- skin rash
- serum sickness
What are the indications & contraindications of radiotherapy in hyperthyroidism?
Indications
- recurrence after thyroidectomy
- failure of medical treatment & unfit patient for surgery
- patients refusing surgery
Contraindications
- pregnancy, lactation, & childhood
- huge & retrosternal goiter
What should be the relationship between antithyroid drugs & radiotherapy?
antithyroid drugs should be stopped 10 days before radiotherapy & retaken 14 days after
- so it does not interfere with the uptake of the radio-iodine
- keep taking antithyroid drugs for a couple of months until the effect of the radiotherapy is apparent
What are the side effects of radiotherapy in hyperthyroidism?
- hypothyroidism
- > if it occurs after 1 month: transient
- > if it occurs after 1 year: permanent
- thyroid carcinoma
- fetal abnormalities & hypothyroidism in newborn if given during pregnancy
What are the indications for surgical subtotal thyroidectomy?
- allergy to antithyroid drugs
- patient refusing radiotherapy
- big & retrosternal goiters
- multi nodular toxic goiter
- malignant suspicion
How should a patient be prepared for thyroidectomy?
- thionamide drugs for several months before
- inorganic iodine 7 - 10 days before surgery
- beta blockers
What are the complications of thyroidectomy?
- hypothyroidism
- hypoparathyroidism
- recurrent hyperthyroidism
- recurrent laryngeal nerve injury
How should hyperthyroidism be treated in pregnancy?
- propyl-thiouracil
- surgical thyroidectomy if necessary ONLY in first or second trimester
- special attention paid to newborn because it can develop hyperthyroidism due to TSI
How is thyrotoxic crises treated?
- ice bags, fluids & electrolytes
- IV dexamethasone
- IV propranolol
- Ipodate (Na update)
- antithyroid drugs in large doses -> propyl thiouracil 600mg then 300mg every 6 hours
- antibiotics
- K-iodide
What are the non goitrous types of hypothyroidism?
- congenital developmental defect
- post surgery
- post radiotherapy
- idiopathic -> antibodies
What are the goiterous types of hypothyroidism?
- Pendred syndrome
- endemic goiter -> iodine deficiency
- maternally transmitted antithyroid drug or radiotherapy during pregnancy
- drug induced
- chronic thyroiditis EARLY in disease
What are the neurological manifestations of myxoedema?
- reduced memory, mental slowing, dementia -> myxedema madness, depression
- delayed relaxation of tendon jerks -> suspended jerks
- mucinous infiltration
- > flexor retinaculum: carpal tunnel syndrome
- > internal ear: progressive deafness
- > vocal cords: hoarseness of voice
- > tongue: slurred speech
What are the cardiovascular manifestations of myxoedema?
- sinus bradycardia -> heart block
- cardiomyopathy -> heart failure
- cholesterol pericarditis & pericardial effusion
- atherosclerosis -> angina pectoris & intermittent claudication
- hypertension -> increased peripheral resistance -> increased diastolic BP
- hypotension only in myxedema coma
- anemia
- > normocytic -> bone marrow depression & decreased peripheral O2 requirements
- > megaloblastic -> pernicious anemia (Vit B12)
- microcytic hypochromic -> menorrhagia & achlorhydria
What are the GIT manifestations of myxoedema?
- dynamic ileus -> constipation, obstruction
- achlorhydria -> pernicious anemia
- ascites -> high cholesterol
What are the musculoskeletal manifestations of myxoedema?
- arthralgia
- joint effusion
- stiff muscles
What are the skin & hair manifestations of myxoedema?
- puffy face & coarse features
- dry cold skin
- orange due to accumulation of carotene
- malar flush
- sparse, brittle course hair
- loss of outer 1/3rd of eyebrow
- xanthelasma
What are the reproductive manifestations of myxoedema?
- menorrhagia
- amenorrhea & galactorrhea (if associated with hyperprolactinaemia) -> increased in TRH
- infertility
What are the pulmonary & renal manifestations of myxoedema?
Pulmonary
- pleural effusion
- decreased ventilatory response to hypoxia & hypercapnia -> CO2 narcosis
Renal
- hyponatremia -> may be due to SIADH
What are the metabolic & endocrinal manifestations of myxoedema?
- growth & developmental retardation in children
- weight gain & decreased appetite
- hypothermia & cold intolerance
- hyperlipidemia
What are the causes of myxoedema coma?
- long standing untreated hypothyroidism
- hypothyroidism with exposure to -> infection, cold, trauma, CNS depression
What is the clinical picture of myxoedema coma?
- subnormal temperature -> 34 - 35
- external features of severe hypothyroidism & bradycardia
- dilutional hyponatraemia
- alveolar hypoventilation -> CO2 retention & narcosis
What investigations are done for myxedema?
- thyroid function
- x-ray -> pericardial or pleural effusion
- ECG -> low voltage, bradycardia
How is myxoedema treated?
L thyroxin -> full effect in 2 - 3 months
- asses T3 & T4 & TSH in 6 weeks
what are the indications for rapid correction of hypothyroidism?
- neonatal, infantile, juvenile
- myxedema coma
- hypothyroid patient preparing for emergency surgery
-> IV administration of L-thyroxin + hydrocortisone
What are the indications for slow correction of hypothyroidism?
- elderly patients
- patients with heart disease
-> start with 25 - 50ug/day -> increase 25-50ug every month -> until reaching 150 - 200ug
How is myxedema coma managed?
- hydrocortisone 100mg FIRST -> incase associated with adrenal insufficiency
- IV L-thyroxin -> 500ug
- assisted ventilation
- avoid further heat loss
What is the cause & clinical picture of subacute thyroiditis? (De Quarvain)
- follows UPPER RESPIRATORY TRACT INFECTION
- pain over thyroid or referred to lower jaw, ear, occiput
- fever, nodular thyroid, dysphagia
What will be found on investigation of subacute thyroiditis & how should it be treated?
- increase T4 due to leakage in the beginning -> euthyroid -> hypothyroid -> recovery
- decreased RAIU
- increased ESR
treat using
- aspirin -> in mild cases
- prednisone 15-20mg & propranolol -> in severe cases
What is chronic lymphocytic thyroiditis?
HASHIMOTO’S -> autoimmune chronic thyroid inflammation
- increase T4 initially -> hypothyroidism later
- high tire of antimicrosomal antibodies -> could lead to Hashitoxicosis
treat using levothyroxin
What are the high risk factors for malignancy in a thyroid nodule?
HISTORY
- head & neck irradiation
- nuclear radiation exposure
- rapid growth
- recent onset
- young age
- male
- familial (medullary then papillary)
PHYSICAL EXAM
- hard nodule
- fixed
- lymphadenopathy
- vocal cord paralysis
- distant metastasis
LAB & IMAGING
- elevated calcitonin
- cold nodule on technetium
- solid lesion with micro calcification on US
