Hyperthyroidism Flashcards
definition
hyperthyroidism refers specifically to conditions in which overactivity of the thyroid gland and excess thyroid hormones leads to thyrotoxicosis
thyrotoxicosis definition
thyrotoxicosis is the clinical, physiological and biochemical state arising when tissues are exposed to excess thyroid hormone
hyperthyroidism and thyrotoxicosis are
not the same thing
symptoms of thyrotoxicosis
- palpitations
- atrial fibrillation
- tremor
- sweating
- anxiety, nervousness, irritability, sleep disturbances
- lid retraction
- double vision (diplopia)
- proptosis/ exophthalmus ( specific to graves disease)
- muscle weakness especially in the thighs and upper arms ]
- weight loss despite increased appetite
- heat intolerance
causes of thyrotoxicosis associated with hyperthyroidism subtypes
excessive thyroid stimulation and thyroid nodules with autonomous function
causes of thyrotoxicosis which cause excessive stimulation of the thyroid gland
- graves disease (most common)
- hashitoxicosis
- thyroid cancer (rare cause)
- choriocarcinoma (type of gestational trophoblastic disease which secreted HCG i.e. trophoblast producing cancer occurring during pregnancy)
causes of thyrotoxicosis which cause a thyroid nodule with autonomous function
- toxin solitaire nodule
- toxic multi-nodular goitre
causes of thyrotoxicosis not associated with hyperthyroidism subtypes
thyroid inflammation, exogenous thyroid hormone, ectopic thyroid tissue
causes of thyrotoxicosis caused by thyroid inflammation
- subacute (de quervains) thyroiditis
- post- partum thyroiditis
- drug induced thyroiditis ( amiodarone)
causes of thyrotoxicosis caused by exogenous thyroid hormones
- overtretment of hypothyroidism with levothyroxine
- thyrotoxicosis factitia (self induced thyrotoxicosis)
causes of thyrotoxicosis caused by ectopic thyroid tissue
- metastatic thyroid carcinoma
- struma ovarii (teratoma containing thyroid tissue)
graves disease is the
number one cause of hyperthyroidism
who is graves disease more common in
8x more common in woman with the average age of onset around 20-40 years old
whats is graves disease
autoimmune hyperthyroidism targeting the TSH receptor
symptoms of graves disease
- all the symptoms of thyrotoxicosis and specific graves symptoms:
- graves opthalmopathy
- pretibial myxoedema
- thyroid acropathy
- thyroid bruit
graves opthalmopathy
occurs in 20% of patients with graves disease and is strongly associated with smoking
- exophthalmus (proptosis): abnormal anterior protrusion of the eyeball
- lid retraction
thyroid bruit
occurs only in graves disease and only if there is an extremely large goitre
laboratory investigations for hyperthyroidism
HIGH T3/T3 LOW TSH
- hypercalcaemia and increased ALP due to T3 activating osteoclasts causing increased bone turnover (graves disease is associated with osteoporosis)
- leucopenia (reduced white cell count)
autoantibodies
- TSH receptor autoantibody (most specific to graves)
- thyroglobulin antibody
- thyroid peroxidase antibody ( anti-TPO)
if TSH receptor antibody is negative then
a radioactive iodine uptake test is required, if the antibody is positive then no scan is required, should show confluent increased uptake in graves disease
first line management of graves disease
propranolol+ carbimazole
why is propranolol used in graves disease
used for symptomatic relief of thyrotoxicosis symptoms but does not treat the underling disease
propranolol is a
non-selective beta blockers which blocks beta 1 and beta 2 adrenoreceptors, it thyrotoxicosis is used because the blockage of beta-1- adrenoreceptors in the heart reduces heart rate, contractility and speed of conduction through the AV node and inhibits D101
who is propranolol used with caution
asthmatics because it can cause bronchospasm as it blocks beta-2-adrenoreceptors causing bronchoconstriction
if propranolol cannot be used what is used
diltiazem which is a calcium channel blocker
when would carbimazole be contra-indicated and what is used instead
during the first trimester of pregnancy as there is a risk of aplastic cutis (absence of areas of skin) so PTU (propiothiouracil) is used instead
mechanism of action of carbimazole and propiothiouracil
after absorption is converted to the active form called methimazole which prevents thyroid peroxidase enzyme (TPO) from iodinating the tyrosine residues on thyroglobulin inhibiting the production of thyroid hormones (T3 AND T4)
rare side effect of propriothiouracil (PTU)
liver failure
theres 2 ways graves can be treated wit anti-thyroid drugs
- dose titration over 12-18 months by starting with a low dose and titrating up
- block and replace (over 6 months) start with a very high dose and induce hypothyroidism over 6 moths and then treat with levothyroxine
side effects of carbimazole and PTU
- 1-5% of people develop an allergic type reaction: rash, urticaria and arthralgia
- cholestatic jaundice, increased liver enzyme and fulminant hepatic failure
- agranulocytosis in 0.1-0.5%
what is agranulocytosis
disorder of bone marrow causing a severe reduction in the number of granulocytes causing a particularly severe neutropenia causing severe bacterial or fungal infections
when is the risk of agranulocytosis highest
in the first 6 months of starting mediation, patient should e warned verbally AND in writing to stop medications and have urgent FBCS if they have a fever, oral ulcer of oropharyngeal infection
medical management of graves disease has a
50% realisation rate
1st line management of graves disease after medical management
radioactive iodine ablation
radioactive iodine ablation is contradicted in
pregnant woman and after treatment woman should not conceive for at least a year
should not be used in graves eye disease as it will worse it (but can be used in milder eye disease if it is first treated with steroids)
radioactive iodine ablation commonly causes what after treatment
hypothyroidism which will then need to be treated with levothyroxine
what is used if radioactive iodine is contraindicated
thyroidectomy
thyroidectomy can
damage the recurrent laryngeal nerve, cause hypoparathyroidism and hypothyroidism
thyroid storm
life threatening form of thyrotoxicosis which mostly occurs in people with untested graves disease when they get an acute infection/illness
laboratory investigations for thyroid storm
T3 AND T4 LEVELS VERY HIGH, TSH IS LOW
presentation of thyroid storm
- sweating
- hypertension initially and in late stages causes hypotension
- hyperthermia
- exaggerated reflexes
- altered mental status (delirium, seizures and coma)
management of thyroid storm
ABCDE
IV PTU
LUGOLS IODINE (works by saturating the thyroid gland)
propranolol
iv fluids
hydrocortisone
toxic nodular thyroid disease caused by
- toxic nodular adenoma
- toxic multi-nodular growth
what is felt on palpation in someone with toxic nodular thyroid disease
nodules felt rather than a goitre
occurs most often in
older patients
investigations for toxic nodular disease
- high T3 AND T4 and low TSH
- antibody negative (TRAb)
- high uptake in radioactive iodine uptake scan
what happens if TSH is normal or the radioactive iodine scan does not show increased uptake
the hyperthyroidism could be caused by thyroid cancer
management of toxic nodular thyroid disease
1st line= radioactive iodine ablation
2nd line= thyroidectomy
why is smoking cessation important
because smoking is the main risk factor for thyroid eye disease
