Week 3 - G - ITA thyroid tutorial Flashcards
Where are thyroid hormones stored?
In the colloid
What is the main plasma protein that T4 and T3 bind to?
Thyroxine binding globulin , less than 0.5% of each is present in the free form which is biologically active
As T4 accounts for 90% of the total thyroid hormones produced and T3 is the major biologically active, how does the main production of T3 take place?
T3 is mainly produced by de-iodination of T4 within target cells outside the thyroid gland. (mainly through D2-deiodinase enzyme)
What enzyme activates iodine to attach to the tyrosine residues?
A thyroid perxoidase enzyme
Once TSH has bound to the receptor on the follicular cell, how does this trigger the release of the thyroid hormones?
Release of thyroid hormones via endocytosis (pinocytosis) is triggered and the thyroglobulin is broken down by lysosomes to release T4 and T3 into the bloodstream
What are 7 causes of goitre?
Grave’s disease Hashimoto’s thyroditis Iodine deficiency Amiodorane Lithium Multi-Nodular goitre Sub-acute thyroditis
What age groups with a thyroid nodule are at an increased worry of malignancy?
Below 20 and above 70 years of age
If the lump is smooth, does this indicate benign or malignant? What about if there is dysphagia? Cervical lymphadenopathy?
If smooth then benign Dysphagia and cervical lymphadenopathy are malignant
What size does the thyroid lump have to be to assess for malignancy or benign? What procedure is used to carry this out?
Greater than 1.5cm Ultrasound guided fine needle aspiration (FNA)
Thyroid Storm (crisis) Untreated or inadequately treated thyrotoxicosis Rare but life threatening Medical emergency - HR increased , BP decreased, Fever , Altered mental status, Multiorgan failure How is it treated? (always rememeber to treat precipitating cause)
Management of thyroid storm Carbimazole –high dose Beta blockers - slow heart Hydrocortisone - reduces peripheral conversion of T4 to T3 Potassium Iodide IV fluids +/- Inotropes Treat precipitating cause e.g MI, Infection, PE
What is the hand, leg and eye conditions associated with grave’s disease?
Hand - thyroid acropachy Leg - pretibial myxoedema Eye - exopthalmos (aka proptosis)
What are the features of dysthyroid eye disease?
Clinical features of dysthryoid eye disease - Grittiness, watery eyes Conjunctival injection Eyelid retraction Proptosis Visual blurring Painful eye movements
When treating patients with (levo)thyroxine for hypothyroidism, usual starting dose is 50-100 micrograms, when is the starting dose lowered to 25micro grams?
Start lower dose if history of IHD or LVF
