Case 7 - Thyroid disease Flashcards
What are the types of hyperthyroidism?
Graves disease Thyroid tumour Post-partum hyperthyroidism Neonatal hyperthyroidism Abnormal thyroid stimulation Due to drugs
What is Graves’ disease?
Most common cause of hyperthyroidism
Autoimmune condition in which TSH-R Abs are made by the body
Stimulates the thyroid to produce more thyroid hormones
Has the characteristic eye signs of Graves’ disease and may produce a diffuse goitre
More likely to have other autoimmune conditions too
Normal or raised uptake on radioactive iodine scan
How can a benign thyroid tumour causes hyperthyroidism?
A small benign tumour can develop in the thyroid and become resistant to the negative feedback on the thyroid gland, and continues to make more thyroid hormones
How can tumours cause hyperthyroidism?
How can abnormal thyroid stimulation cause hyperthyroidism?
May produce a multinodular goitre
Usually in those >40y
Tumour of the thyrotrophic cells releases excess hormones
hCG particularly in pregnancy can mimic TSH and act at the receptors to stimulate the thyroid gland to produce thyroid hormones
How can drugs cause hyperthyroidism?
Interferons and amiodarone can cause it
What is post-partum hyperthyroidsim?
Sub-type of hashimotos Milder symptoms than in Graves' TPO Abs are made Decreased uptake of radioiodine Rarely requires treatment, just beta blockers for symptoms
What is neonatal hyperthyroidism?
When TSH Abs crosses the placenta to stimulate the fetus’ thyroid gland
What are the signs and symptoms of hyperthyroidism?
Anxious/Agitated Tachycardia Difficulty sleeping Tremor Intolerant to heat Hyperreflexia Conjunctival oedema Pretibial myxoema Proximal myopathy Acropachy Exophthalmos Omphthalmoplegia Weight loss
What are RFs for hyperthyroidism?
Female <40y Emotional/physical stress Smoker Pregnant Other autoimmune conditions FHx of thyroid disease
What are the treatment options for hyperthyroidism?
Beta blockers
Anti-thyroid drugs
Radioactive iodine
Thyroidectomy
What are the complications of hyperthyroidism?
Pregnancy - can lead to neonatal hyperthyroidism. Also pre-eclampsia, miscarriage, maternal HF
Arrythmias - AF can be caused by hyperthyroidism
Thyrotoxic crisis - rare and drastic, where a sudden increase in thyroid hormones leads to adrenergic symptoms
Osteoperosis
How do antithyroid drugs treat hyperthyroidism?
PTU or carbimazole
PTU take 3x a day, carbimazole once a day
Treat until T4 levels within range
Titrate dose down or block-replace (can’t do in pregnancy)
SEs- rash, itching, arthalgia, get pts to report infections as there’s a risk of agranulocytosis
How does radioactive iodine treat hyperthyroidism?
Taken as a drink
The iodine moves into the thyroid and reduces the activity of the cells by destroying them
Cannot sleep in the same bed as people, be around pregnant women or children etc. for significant periods of time
Eventually become hypothyroid
How does a thyroidectomy work?
Can be partial or total
Risks dependent on surgeon - can get recurrent laryngeal nerve damage
Will get subsequent hypothyroidism - need to take T4 post-op
Low relapse rate
How does the thyroid produce thyroid hormones?
Anterior pit gland makes TRH
TRH activates hypiothalamus to make TSH
TSH binds to G protein coupled receptor
Activates adenylyl cyclase to activate cAMP
Thyroglobulin made and secreted into colloid
Iodine moved into colloid using pendrin transporter
Combined with thyroglobulin using TPO
Thyroglobulin taken into cells
Broken down into T3 and T4
These are in circulation bound to thyroid binding hormones
Only free hormone can act on the tissues
T3 made 10x more by gland and is more effective at the tissues than T4 - T4 converted to T3 to act on cells
