Hyperthyroidism Flashcards
Outline the function of a thyroid follicular cell
Anterior pituitary releases TSH which activates iodide uptake. TSH also activates proteolytic enzymes causing release of T3 and T4
What are the general symptoms of hyperthyroidism?
Weight loss despite increased appetite, breathlessness, palpitations, tachycardia, tremor, increased sweating, diarrhoea, lid lag and heat intolerance
What are the 4 main causes of hyperthyroidism?
Graves’ disease.
Plummers disease - toxic solitary nodule or multinodular.
Viral thyroiditis
Post-natal thyroiditis
Outline the pathophysiology of Graves’ disease and what specific symptoms this causes
Autoimmune disease where antibodies bind to and stimulate the TSH receptor in the thyroid. Causes smooth goitre, exopthalmos and pretibial myxoedema
What is seen in the thyroid scan of a patient with Graves’ disease
Uniform uptake
Outline the differences seen in blood hormone levels between primary and secondary hyperthyroidism
Primary = low T3/T4, high TSH
Secondary = low T3/T4, low TSH
Outline the actions of thyroid hormone
Essential for foetal growth and development. Increases basal metabolic rate and cardiac output
Outline the pathophysiology of Plummers disease
Toxic nodular goitre, not autoimmune but due to benign adenoma that is overactive
What difference in symptoms are there between Plummers disease and Graves’ disease?
In Plummers no pretibial myxoedema or exophthalmos, unilaterally large goitre
What does the pituitary gland of a patient with Plummers disease look like?
Unilateral lump, rest of gland atrophies
What would a radioiodine uptake test look like in a patient with Plummers disease
A single or multiple hot nodules
Outline the effects of thyroxine on the sympathetic nervous system
T3 makes beta adrenoreceptors sensitive to ambient levels of adrenaline and noradrenaline. This causes tachycardia, palpitations, tremor and lid lag
What is thyroid storm and what are the symptoms
Thyroid storm results from hyperthyroidism being left untreated. It is a medical emergency with 50% mortality rate. Is blood result confirmed hyperthyroidism plus: hyperpyrexia, tachycardia, cardiac failure, delirium, jaundice. Needs aggressive treatment.
What are the treatment options for hyperythyroidism?
Thyroidectomy, radioiodine, drugs
What drugs are used to treat hyperthyroidism?
Thionamides (PTU and CBZ). Potassium iodide. Radioiodine and non-selective B-blockers
What is the benefit of non-selective beta-blockers being used to treat hyperthyroidism?
Help stop tremors aswell as tachycardia
Outline the mechanism of action of thionamides
Inhibit thyroid peroxidase and hence T3/T4 secretion. Has instant biochemical effects but physical effect can take a month as T4 hormones already stored
What are the adverse effects of thionamides?
Agranulocytosis - suppression of the immune system, can lead to sepsis and rashes, reversable.
Outline the risks associated with a. Thyroidectomy
Risk of voice change - recurrent laryngeal nerve lesion. Risk of losing parathyroid glands
Outline the 6 steps of thyroid hormone synthesis
TSH binds to receptors causing TG production and TPO activation - transported into the colloid.
Iodide ions diffuse into colloid.
TPO oxidises I- into I2
TPO attaches I2 into tyrosine residues on the thyroglobulin producing MIT and DIT.
Iodinated tyrosines link together forming thyroid hormones.
Lysosomal enzymes remove thyroglobulin from thyroid hormones
What are the clinical uses of potassium iodide?
Preparation of hyperthyroid patients for surgery.
Severe thyrotoxic crisis (thyroid storm)
Should only be used temporarily (10 days)
What precautions need to be put in place for radioiodine treatment?
is contraindicted in pregnancy, have to avoid children and pregnant women for 7 days due to radiation
Outline the pathophysiology of viral thyroiditis
virus attacks follicular thyroid gland causing pain. No iodine uptake causing all stored thyroxine to be released. Free T4 levels rise, TSH drops for a month of hyperthyroidism. FT4 falls and patient becomes hypothyroid, body recovers naturally
what are the key clinical features of viral thyroiditis?
painful dysphagia, hyperthyroidism, pyrexia, thyroid inflammation
