Endo 5 - Hyperthyroidism Flashcards
Describe Plummers disease (a form of hyperthyroidism)
- Toxic nodular goitre caused by benign adenomas
2. NOT AUTOIMMUNE - therefore no exophthalmos or pretibial myxoedema
What does thyroxine do to the SNS
It sensitises the Beta receptors = little bit of A/NA has massive effects
Looks like there is SNS activation, may manifest as palpitations, tremor, lid lag etc
If someone has a family history of hyperthyroidism, its more likely to be graves or plummers?
Graves (as autoimmune aspect)
What are some common symptoms of hyperthyroidism?
Weight loss w increased appetite Breathlessness Palpitations/tachycardia Sweating Heat intolerance DIarrhoea Lid lag
Thyroid storm is what?
requires aggressive treatment
Extreme hyperthyroidism with 2 of the following 5:
- Hyperpyrexia > 41*C
- Accelerated tachycardia
- Cardiac failur
- Delirium/ psychosis
- Hepatocellular dysfunction - jaundice
What are the treatment options for hyperthyroidism?
Surgery / radioiodine / drugs
What are the 4 classes of drugs used to treat hyperthyroidism?
- Thionamides (propylthiouracil (PTU) / Carbimazole (CBZ))
- Potassium iodide
- Radioiodine
- Beta blockers
1-3 = reduce thyroid hormone synthesis
4 = symptoms relief
When would you use thionamides?
- Daily treatment of hyperthyroid conditions, or before surgery or short term while waiting for radioactive iodine to act
How do thionamides (aka anti-thyroid drugs) work?
Inhibit thyroid peroxidase enzymes - slows down T3/4 synthesis and secretion
How long do thionamides take to have a clinical effect?
Weeks, although biochemical effect within hours
Does hyperthyroidism require a cardioselective or non-cardioselective B blocker?
Non cardioselective - e.g. propranolol
Thionamides may do 2 other things in addition to inhibiting peroxidase enzymes. They are?
- Suppress antibody production in graves disease
2. PTU may reduce conversion of T4 to T3 peripherally
What are some unwanted actions of antithyroid drugs
- Agranulocytosis (reduction in neutrophils) - rare and reversible if drug withdrawn
- Rashes (common)
PTU and Carbimazole are antithyroid drugs (thionamides). They are orally active. When pregnant, what must you consider?
Both PTU and carbimazole cross the placenta and are secreted in breastmilk, so lower doses. PTU crosses less into placenta and less secreted, so PTU preferred
Carbimazole is a prodrug which is converted into?
Methimazole
Where are antithyroid drugs metabolised and excreted?
Metabolised in liver and excreted in urine
How long should antithyroid treatment be?
18 months, then periodically check for relapse
When would you give KI to a patient
In severe thyrotoxic crisis
Or to prepare a hyperthyroid patient for surgery
Explain the mechanism of action of KI
- Inhibits iodination of thyroglobulin
- Inhibits thyroperoxidase and peroxide generation
WOLFF-CHAIKOFF effect - auto regulatory effect whereby body shuts down T4 production if exposed to too much iodine
How long does KI take to work?
Symptom reduction in 1-2 days
Vascularity and size reduction of thyroid in 10-14 days
KI ONLY USED VERY SHORT TERM
What are the unwanted actions of KI?
- Allergic reaction
When is radioiodine given?
When antithyroid drugs don’t work after 18 months.
How does radio iodine work?
Accumulates in colloid, emits B particles and destroys follicular cells
How is radio iodine given?
Given asa single oral dose
