2.4 Diagnosis and Treatment of Thyroid Disorders Flashcards
Where is thyroglobulin synthesised? Where does it react with iodine? Is the iodine always in this form?
- Synthesised in thyroid follicular cells
- Tyrosine residues from thyroglobulin react with iodine to form thyroid hormones
- No; the iodine starts are I- (iodide), and is converted within the colloid by TPO
This supplement can interfere with thyroid function testing, and should be witheld prior to blood tests for thyroid panel…
Biotin
In order for hyper/hypothyroidism to be considered “subclinical”, what must T3/T4 levels be? TSH?
- Both normal
- If TSH is high, this is subclinical hypothyroidism (not enough neg feedback)
- If TSH is low, this is subclinical hyperthyroidism
Explain the mech of gestational hyperthyroidism. Does it self-resolve?
- hCG can bind to TSH receptors and act like a weak form of TSH
- Will self-resolve after pregnancy
This type of thyroiditis is especially common after an infection
Subacute thyroidits
A patient is medicated for AF, and shows signs of hyperthyroidism. What medication might they be taking, specifically? Why do we think this?
Amiodarone. Amiodarone contains relatively large amounts of iodine as % weight, so can cause increased synthesis of thyroid hormones -> hyperthyroidism
Which class of drug is used to acutely slow conversion of T4 to T3 during thyroid storm?
Glucocorticoids
Which antithyroid drug can be given during the first vs second and third pregnancy trimesters?
During first: Propylthiouracil can be given (NOT carbimazole)
During second two: carbimazole can be given
{PT = Prior To = First}
What are the three kinds of thyroid-related autoantibody that we see (in terms of target)?
- Thyroglobulin
- Thyroid peroxidase
- TSH receptor (can be inhibitory, excitatory, or neutral)
What is the typical action of thyroid peroxidase (TPO)?
- Enables production of DIT and MIT
- Essentially, enables production of T3 and T4
What are some indications for radioactive iodine uptake scan of the thyroid? What isotopes are used? How does it work?
- Indicated to find the cause of hyperthyroidism, and to determine if a nodule is hot/cold
- Uses I-123 or (more commonly) I-131
- Scan tells us which tissue is taking up iodine to produce thyroid hormones, helping to determine activity levels of various tissue
What’s the difference between radioiodine uptake scans and -therapy?
The therapy uses much stronger radiation, enabling it to kill cells instead of just visualising uptake.
What are some criteria of the Thyroid Imaging Reporting DAta System (TIRADS)? Why is it used? How does the scoring system work?
- Used by radiologists to measure criteria such as echogenicity, shape, margin, composition of thyroid
- Scoring system enables assessment of risk on a scale of TR1-TR5; for TR3 and above, fine needle aspirate is indicated, otherwise observations instead
What are the indications for thyroid CT?
- Evaluation of suspected cancer (?metastases)
- Determining size and extent of goiter (?compression of surrounding structures)
Explain the mech for propylthiouracil (PTU) and carbimazole
- Inhibits thyroperoxidase
- This inhibits thyroid hormone synthesis
