Hyperthyroidism Flashcards
What is the causes of Grave’s disease?
Autoimmune - antibodies bind to and stimulate TSH receptors in the thyroid
What happens to the body in Grave’s disease?
Stimulation of gland causes growth and forms a smooth goitre
Also causes lid lag
Other antibodies bind to muscles behind the eyes and cause exophthalmos
Other antibodies cause pretibial myxoedema
Non pitting oedema
What is the cause of Plummer’s disease?
Not autoimmune - a benign adenoma
What is different in Plummer’s disease to Graves?
Toxic nodular goitre which no pretibial myxoedema and no exophthalmos and is also called a ‘hot nodule’ on a thyroid uptake scan
What are signs and symptoms of general hyperthyroidism?
Everything SPEEDS UP Weight loss Dyspnoea Palpatations, tachycardia Sweating and heat intolerance Diarrhoea Lid lag and other SNS features
How does hyperthyroidism lead to apparent SNS activation?
Thyroxine sensitises beta-adrenoceptors to ambient levels of adrenaline and noradrenaline (not more adrenaline, just more sensitive receptors) which leads to the SNS activation
What is Viral (de Quervains) Thyroiditis?
Painful/tender dysphagia with hyperthyroidism and prexia - fever and a raised erythrocyte sedimentation rate
How can hyperthyroidism become hypothyroidism after a month in Viral (de Quervains) Thyroiditis?
Virus attacks thyroid gland causing pain and tenderness, then the virus lyses the cell and thyroxine spills out into the blood (hypertension) and then the thyroid is not creating thyroxine hyper -> hypothyroidism
What is shown on an uptake scan in Viral (de Quervains) Thyroiditis?
ZERO iodine uptake
What is a thyroid storm? What are the signs and symptoms?
Medical emergency!! Hyperpyrexia – high fever (>41). Accelerated tachycardia/arrhythmia. Cardiac failure. Delirium/frank psychosis. Hepatocellular dysfunction, jaundice
What is the treatment for a thyroid storm?
Surgery (thyroidectomy)
Radioiodine
Drugs
What are the three drugs that inhibit thyroxine synthesis?
Thionamides
Potassium iodide
Radioiodine
What are 2 examples of thionamides? What are they?
Propylthiouracil
Carbimazole
which are anti-thyroid drugs
What is the clinical use of thionamides?
Daily treatment of hyperthyroid conditions eg grave’s
Treatment prior to surgery
Reduction of symptoms while waiting for radioactive iodine to act
What is the mechanism of action of thionamides?
Inhibits TPO and peroxidase transaminase
Suppress antibody production in graves
Reduce T4 -> T3 in peripheral tissues
What is the difference between the biochemical and clinical effects of thionamides?
There is a biochemical effect in hours but no clinical effect until a week or so has passed so there is a large store of normal thyroxine in the thyroid gland which is released for a while
What other drug is usually paired with thionamides in a treatment plan for hyperthyroidism?
Propanolol which is a beta blocker to rapidly reduce treamours and tachycardia
What are unwanted actions of thionamides?
Agranulocytosis - reduction or absence of granular leukocytes
Rashes
What is the pharmacokinetics of thionamides? (administration? half life? metabolize rate?)
Orally active prodrug that has a plasma half life of 6-15 hours and crosses the placenta so is secreted in breat milk and metabolised in liver and secreted in urine
What is the follow up for thionamides?
Stop anti thyroid treatment after 18 months and review patient frequently
When is iodine treatment of KI used in hyperthyroidism?
Preparing the hyperthyroid patient for surgery
In severe thyroid storm crisis
What is the mechanism of action of iodine treatment for hyperthyroidism?
Inhibit iodination of TG
Inhibit hydrogen peroxide generation
WOLF CHAIKOFF EFFECT
What are unwanted reactions of KI treatment for hyperthyroidism?
Allergic reactions
What are the pharmacokinetics of KI treatment for hyperthyroidism? (administration? When is maximum effect?)
Orally active - lugol’s solution with maximum effect after 10 days of continuous administration
