Thyroid 3 Flashcards
(49 cards)
What labs should be checked before starting MMI?
- CBC/d
- LFTs
What are the side effects of methimazole? Which one is most common?
- Rash (most common)
- Bone marrow suppression
- Liver toxicity
What is the dose of MMI?
0.1 to 1.0 mg/kg/d although typical is 0.2-0.5
Which beta blockers are used to tx Graves disease and how are they different?
- Propranolol: Non-selective (blocks both B1 and B2 receptors), blocks conversion of T4 –> T3. Don’t use in patients w/ asthma.
- Atenolol: Cardioselective (blocks B1 only). Given once per day.
- Metoprolol XR: Cardioselective (blocks B1 only) with CNS penetration, so give if there is psychosis or significant anxiety.
How often do you check labs in neonatal vs regular Graves after starting treatment? When do you start the wean MMI dose?
- Neonates: Weekly until stable, then every 2 weeks
- Regular: Every 2-6 weeks
- In either group, begin to wean once T3 and T4 in normal range
When do you check TFTs in newborns if there is concern for neonatal Graves?
- The first 3-5 DOL or sooner if concerned.
- If normal, repeat at 10-14 DOL. If still normal, then at 1, 2, and 3 MOL given risk of delayed presentation.
What does a TSH adenoma cause? How do you rule it out?
- Hyperthyroidism
- Alpha glycoprotein
How can GH affect thyroid hormone production? When should you check TFTs during GH therapy?
- GH causes increased somatostatin production, which will then decreased TSH mimicking central hypothyroidism.
- Check TFTs 3 mos after starting GH and then annually thereafter.
What dose of levothyroxine should be used when treating central hypothyroidism?
1.6 mcg/kg/d
How often do you dose levothyroxine?
- Neonates: 10-15 mcg/kg/d
- 3-6 MOL: 8-10 mcg/kg/d
- 6-12 MOL: 6-8 mcg/kg/d
- 1-5yo: 5-6 mcg/kg/d
- 6-12yo: 4-5 mcg/kg/d
- 12+ years w/ incomplete growth and puberty: 2-3 mcg/kg/d
- Max: 100-200 mcg/d
What are the ultrasound findings like in patients w/ Hashimoto’s?
- Enlarged thyroid
- Heterogeneous
- Hypoechoic micronodules (“cobblestoning”)
What is Van Wyk-Grumbach syndrome?
- Long-standing hypothyroidism –> elevated TSH –> TSH stimulates alpha subunit of FSH receptors leading to vaginal bleeding or testicular enlargement. TRH can also increase prolactin levels.
- Phenotype: Looks like precocious puberty yet bone age is delayed.
- Labs: FSH high, LH low because prolactin is high, TRH and TSH high
What is cystinosis?
- AR lysosomal storage disease due to mutation in CTNS on chromosome 17 that leads to crystal formation throughout the body.
- Phenotype: Primary hypothyroidism + photophobia + renal Fanconi’s
How does Lithium affect the thyroid?
- Hypothyroidism w/ goiter (more common than hyperthyroidism) due to inhibition of thyroid hormone synthesis and secretion OR by enhancing effects of underlying autoimmune thyroid disease.
- Hyperthyroidism due to transient and painless thyroiditis OR by inducing thyroid autoimmunity.
What is the half-life of amiodarone? How long does it take for iodine stores to return to normal after stopping it?
- 100d
- 6-9 mos
How does amiodarone affect the thyroid?
Hypothyroidism by:
- Inhibiting conversion of T4 –> T3 (happens right away)
- Inhibiting thyroid hormone synthesis and secretion via Wolff-Chaikoff effect (3-6 mos later)
- In general, occurs during first year of tx.
Hyperthyroidism by:
- Type 1 AIT: Exacerbates underlying Graves disease AND escape from Wolff-Chaikoff. Look for nodular goiter.
- Type 2 AIT: IL-6 destroys thyroid follicular cells with release of thyroid hormone (similar to Hashitoxicosis). Thyroid will be of normal size w/ normal U/S.
- In general, occurs mos to 3 yrs after starting tx.
What is the Wolff-Chaikoff effect?
- Protective mechanism that occurs when body is exposed to excess iodine.
- Works by inhibiting organification of iodine, thus lowering production of T4 and T3.
- Last weeks to months but eventually wears off (Wolff Chaikoff escape).
Which drugs decrease TSH production? Increase?
Decrease TSH = Little DOppy DOG
- Lithium, Dopamine, Octreotide, Dopamine agonists (bromocriptine, cabergoline), Opiates, Glucocorticoids
Increases TSH = My Low Cortisol
- Metoclopramide (reglan, which is a dopamine agonist) + Low Cortisol (Addison’s)
Which medications cause primary hypothyroidism?
CROPPs Grow ___ in the Little ___ GAPP
- Increased clearance due to increased hepatic p450 activity: Carbamazepine, Rifampin, Oxcarbazepine, Phenobarb, Phenytoin, GH
- Decreased production of thyroid hormone: Lithium
- Disrupts peripheral metabolism: Glucocorticoids, Amio, PTU, Propanolol
How does a hepatic hemangioma affect the thyroid?
Increased Type 3 deoidinase activity (T4 –> rT3, T3 –> T2) leads to consumptive hypothyroidism
What causes a goiter in newborns?
iodine deficiency or dyshormonogenesis
What is subacute thyroiditis?
- AKA DeQuervain’s thyroiditis
- Occurs 2-8 weeks after a viral infection
- Hyperthyroid –> euthyroid –> hypothyroid –> euthyroid
- Exam: Non-tender or tender goiter w/ radiation up the neck to throat/ear/jaw.
- Labs: Depends on what stage you’re in.
- Scintigraphy: Low uptake.
- Tx: NSAIDs +/- steroids +/- BB. Don’t use thionamides. If a patient becomes hypothyroid, start LT4.
What is acute suppurative thyroiditis?
- Infectious thyroiditis due to bacteria from L pyriform sinus fistula (strep > staph > anaerobic). Sometimes also due to fungal infection.
- Exam: Painful and warm thyroid.
- Labs: TFTs all over the place.
- Tx: Abx +/- I&D.
In what order are pituitary hormones lost due to cranial radiation?
Good Luck, Fucking Act Tough
- GH > LH/FSH > ACTH > TSH
