Hyperthyroidism, Hypothyroidism and Thyroiditis Flashcards
what causes secondary thyroid disease
hypothalamic or pituitary disease
what is thyrotropin
thyroid stimulating hormone
what makes up 80% of TSH
T4- biologically inactive
what plasma proteins does TSH bind to
TBG, albumin, pre albumin
what is TSH released in response to
TRH
what happens to TSH when you are hypothyroid
is increased in attempt to get euthyriod
what is diodination
removal of iodine - T4 into T3
what are hormone levels like in primary hypothyroidism
free T3/4 low
TSH high
what are hormone levels like in primary hyperthyroidism
free T3/4 high TSH low (often 0)
what are hormone levels like in secondary hypothyroidism
free T3/4 low
TSH low/ normal
what are hormone levels like in secondary hyperthyroidism
free T3/4 high
TSH high/ normal
what is myxoedema
either
coma-severe hypothyroidism, a medical emergency
or
swelling of the skin and underlying tissues giving a waxy consistency, typical of patients with underactive thyroid glands.
what is pretibial myxoedema
sign of graves disease (hyperthyroidism) - infiltrative dermopathy resulting in localised lesions of the skin
what ethnicity is hypothyroidism most common in
white populations
what are the causes of primary goitrous hypothyroidism
chronic thyroiditis (hashimotos), iodine deficiency, drug induced (amiodarone, lithium), maternally transmitted (antithyroid drugs e.g. for graves), hereditary biosynthetic defects
what are the causes of primary non- goitrous hypothyroidism
atrophic thyroiditis (untreated hashimotos), post ablative therapy (radioiodine, surgery), post-radiotherapy (lymphoma treatment), congenital developmental defect
what are the causes of primary self limiting hypothyroidism
withdrawal of antithyroid drugs, subacute thyroiditis with transient hypothyroidism, post partum thyroiditis
what is hashimotos disease
autoimmune hypothyroidism - autoimmune destruction of thyroid gland and reduced thyroid hormone production
what characterised hashimotos (antibodies and histologically)
antibodies against thyroid peroxidase (TPO)
T cell infiltrate and inflammation microscopically
what are the clinical features of hypothyroidism in the hair and skin
coarse sparse hair,
dull expressionless face,
periorbital puffiness,
pale cool skin that feels doughy to touch,
vitiligo may be present (another autoimmune disease),
hypercarotenaemia (yellowing of the skin)
what are the clinical features of hypothyroidism in thermogenesis
cold intolerance
what are the clinical features of hypothyroidism in fluid balance
fluid retention- pitting oedema
what are the cardiac clinical features of hypothyroidism
reduced heart rate, cardiac dilatation, pericardial effusion, worsening of heart failure
what are the metabolic clinical features of hypothyroidism
hyperlipidaemia, decreased appetite, weight gain
what are the GI clinical features of hypothyroidism
constipation, (megacolon, intestinal obstruction, ascites)
what are the respiratory clinical features of hypothyroidism
deep hoarse voice, macoglossia, obstructive sleep apnoea
what are the neurological clinical features of hypothyroidism
decreased intellectual and motor activities, depression, psychosis, neuro-psychiatric, muscle stiffness, cramps, peripheral neuropathy, prolongation of tendon jerks, carpal tunnel, cerebellar ataxia, encephalopathy, decreased visual acuity
what are the gynae/ reproductive clinical features of hypothyroidism
menorrhagia, later oligo- or amenorrhoea, hyperprolactinaemia (increased TRH causes increased PRL)
what other lab abnormalities are seen in primary hypothyroidism
increased MCV
increased CK
increased LDL cholesterol
hyponatraemia (decreased tubular water loss)
hyperprolactinaemia (increased TRH and increased PRL)
what antibodies for graves
anti TPO (70-80%)
anti-thyroglobulin (30-50%)
TSH receptor antibody (70-100%) (stimulating
what antibodies for autoimmune hypothyroidism
anti TPO (95%)
anti-thyroglobulin (60%)
TSH receptor antibody (10-20%) (blocking)
what might rapid restoration of metabolic rate from hypothyroidism precipitate
cardiac arrhythmias
what is the management for hypothryoidism
slowly restore metabolic rate
Younger patients: start levothyroxine at 50-100 μg daily
In the elderly with a history of IHD: start levothyroxine at 25-50 μg daily, adjusted every 4 weeks according to response
when should you check TSH when managing hypothyroidism
2 months after changing dose
if stable every 12-18 months
how do you manage secondary hypothyroidism
titrate dose of levothyroxine to the fT4 level
what is levothyroxine
T4
when should levothyroxine be taken
preferable before breakfast
what can require the levothyroxine dose to be increased
pregnancy
who usually gets myxoedema coma
elderly women with longstanding hypothyroidism that is frequently unrecognised or untreated
what is seen on ECG in myxoedema coma
bradycardia, low voltage complexes, varying degree heart block, T wave inversion, prolongation of the QT interval
what are the resp signs of myxoedema coma
Type 2 respiratory failure: hypoxia, hypercarbia, respiratory acidosis
how do you treat myxoedema coma
ABC passively warm to raise body temp cardiac monitoring for arrhythmias monitor: urine output, fluid balance, central venous system pressure, blood sugars, oxygenation broad spectrum antibiotics thyroxine cautiosly
what precipitates myxoedema coma
when the body compensatory mechanism to hypothyroidism are overwhelmed by e.g an infection
what is thyrotoxicosis
when tissues are exposed to excess thyroid hormone
what is hyperthyroidism
conditions in which overactivity of the thyroid gland leads to thyroidtoxicosis
what are the cardiac symptoms of thyrotoxicosis
palpation, AF, cardiac failure (rare)
what are the sympathetic symptoms of thyrotoxicosis
tremor, sweating
what are the CNS symptoms of thyrotoxicosis
anxiety, nervousness, irritability, sleep disturbance
what are the GI symptoms of thyrotoxicosis
frequent loos bowel movements
what are the vision symptoms of thyrotoxicosis
lid retraction, double vision (diplopia), proptosis (graves)
what are the hair and skin symptoms of thyrotoxicosis
hair change (brittle, thin hair), rapid fingernail growth
what are the reproductive symptoms of thyrotoxicosis
menstrual cycle changes, lighter bleeding and less frequent periods
what are the muscular symptoms of thyrotoxicosis
muscle weakness- esp in upper arms and thighs
what are the metabolic symptoms of thyrotoxicosis
weight loss despite increased appetite
what are the thermogenesis symptoms of thyrotoxicosis
intolerance to heat
what can cause excessive thryoid stimulation
graves disease, hashitoxicosis, thyrotropinoma (TSHoma rare), thyroid cancer (rarely causes thyrotoxicosis), choriocarcinoma (trophoblast tumour secreting hCG (similar to TSH))
what are the types of thyroid nodules with autonomous function
toxic solitary nodule, toxic multinodular goitre
what are the cases of thyrotoxicosis associated with hyperthyroidism
excessive thyroid stimulation and thyroid nodules with autonomous function
what are the cases of thyrotoxicosis not associated with hyperthyroidism
thyroiditis, exogenous thyroid hormones, ectopic thyroid tissue
what can cause thyroid inflammation (thyroiditis)
subacute (de Quervain’s) thyroiditis (self limiting viral condition),
post partum thyroiditis (self limiting),
drug induced (amiodarone (contains iodine))
what can cause exogenous thryoid hormones to cause thyrotoxicosis
over treatment with levothyroxine,
thyrotoxicosis factitia
what can lead to the production of ectopic thyroid tissue causing thyrotoxicosis
metastatic thyroid carcinoma, struma ovarii (teratoma containing thyroid tissue)
who gets graves
slightly more common in women,
20-50 years
what are the risk factors for graves
genes (70%) + environment
sister and children of women with graves
smoking important
what other lab abnormalities are seen in graves
hypercalcaemia and increased alkaline phosphate (increased bone turnover- graves associated with osteoporosis),
leucopenia,
TSH receptor antibody
what clinical signs are specific to graves
pretibial myxoedema, thyroid acropachy, thyroid bruit, graves eye disease (unilateral or bilateral)
what causes a thyroid bruit
only large goitre in graves- reflects the hypervascularity of the thyoid
not heard in other goitrous conditiond
what is graves eye disease associated with
smoking- really important to stop
how is graves eye disease treated
mild- topically (e.g. lubricants)
more severe- steroids, radiotherapy, surgery
is graves eye disease bad
can be sight threatening
how many people with graves get graves eye disease
20%
what is the onset for nodular thyroid disease
insidious onset
who gets nodular thyroid disease
older patients
what does nodular thyroid disease feel like
thyroid feels nodular, asymmetrical goitre (smooth in graves)
what test results are seen in nodular thyroid disease
increased fT3/4, decreased TSH
antibody negative (TRAb),
scintigraphy high uptake,
thyoid ultrasound
what is a thyroid storm
medical emergency (ABC) severe hyperthyroidism causing: -respiratory and cardiac collapse -hyperthermia -exaggerated reflexes -(may require mechanical ventilation)
who gets a thyroid storm
hyperthyroid patients with an acute illness/ infection or recent thyroid surgery
what is the treatment for a thyroid storm
lugols iodine, glucocorticoids, PTU, beta blockers, fluids, monitoring
what are the antithryoid drugs used to treat hyperthyroidism
carbimazole (1st line)
propylthiouracil (PTU) (first line in 1st trimester pregnancy)
how to antithyroid drugs work
inhibits TPO (enzyme helps produce thyroid hormones)
what are the side effects of anti thyroid drugs
well tolerated
1-5% rash, urticaria, arthralgia
cholestatic jaundice, increased liver enzymes, fulminant hepatic failure,
agranulocytosis (rare but warm patients for fever, oral ulcer or oropharyngeal infection)
what is used for immediate symptomatic treatment for hyperthyroidism
beta blockers- propanalol (reduce activity of sympathetic nervous system)
CCB in those with asthma
when is radioiodine used to treat hyperthyroidism
in relapsed graves disease and nodular thyroid disease
never in pregnancy
when is a thyroiectomy used for hyperthyroidism
when radioiodine is CI
what are the risks of a thyroidectomy
recurrent laryngeal nerve palsy, hypothyroidism, hypoparathyroidism
what can cause thyroiditis
Hashimoto’s De Quervain’s/subacute (viral) Post-partum Drug-induced (amiodarone, lithium) Radiation Acute suppurative thyroiditis (bacterial)
who gets subacute thyroiditis
females more than males, 20-50, can be triggered by viral infection
what are the symptoms or subacute thyroiditis
neck tenderness, fever, viral symptoms, self limiting over a few months
where in UK does hypothyroidism occur
in iodine rish areas
where in UK does hyperthyroidism occur
in iodine deficient areas
describe subclinical hypothyroidism
increased TSH, normal fT3/4, risk of developing into overt hypothyroidism treatment advised (always in pregnancy)
describe subclinical hyperthyroidism
decreased TSH, normal fT3/4, risk of developing into overt hyperthyroidism
treatment advised, associated with osteoporosis and AF, seen in multinodular goitres
what is non thyroidal illness
when illness impacts the HPT axis- TSH typically suppressed initially then rises during recovery
68 yr old lady Tiredness Weight gain Slowness Goitre
TSH 42 mU/L
Free T4 4 pmol/L
Normal Results:
TSH 0.4-4.0 mU/L
Free T4 9.8-18.8 pmol/L
Primary hypothyroidism
68 yr old lady
Family history of thyroid disease
Tiredness
Goitre
TSH 12 mU/L
Free T4 11 pmol/L
TPO Antibodies 200 (elevated)
Normal Results:
TSH 0.4-4.0 mU/L
Free T4 9.8-18.8 pmol/L
Subclinical hypothyroidism
52 yr old male Headache Visual field defect Dizziness/weakness Poor libido/loss of erections TSH 0.20 mU/L Free T4 6 pmol/L
Normal Results:
TSH 0.4-4.0 mU/L
Free T4 9.8-18.8 pmol/L
Pituitary tumour causing secondary hypothyroidism
32 yr old lady Weight loss and tremor Feels tired Sleep disturbance TSH <0.01 mU/L Free T4 54 pmol/L
Normal Results:
TSH 0.4-4.0 mU/L
Free T4 9.8-18.8 pmol/L
Graves’ disease
70 yr old lady Diagnosed with atrial fibrillation No symptoms TSH <0.01 mU/L Free T4 26 pmol/L
Normal Results:
TSH 0.4-4.0 mU/L
Free T4 9.8-18.8 pmol/L
Toxic multinodular goitre
32 yr old Sore throat and febrile illness Tired, weight loss, poor sleep GP blood tests: TSH<0.01, T4 36 pmol/L Seen in clinic 6 weeks later TSH 12 mU/L, Free T4 9 pmol/L
Normal Results:
TSH 0.4-4.0 mU/L
Free T4 9.8-18.8 pmol/L
Subacute thyroiditis
