Thyroid Disorders Flashcards
What can occur if there is suboptimal thyroid functioning during growth & development?
- mental retardation
- dwarfism
How is most T3/T4 circulated?
- highly protein bound
When is T3/T4 physiologically active?
- only when it is free
What drugs decrease TSH secretion?
- DA
- glucocorticoids
- octreotide
What drugs decrease T3/T4 secretion?
- Li
- I
- radiocontrast dyes
- amiodarone (can also increase T3/T4)
What are the hyperthyroid disorders?
- Graves
- multi-nodulare toxic goiter
- thyrotoxicosis
What are the types of hypothyroid disorders?
- primary
- secondary
What are the types of primary hypothyroid disorders?
- Hashimoto’s
- iatrogenic
What are the types of secondary hypothyroid disorders?
- pituitary dz
- hypothalmamic dz
What is the hallmark sign of hyperthyroidism?
- wt loss w/ increased appetite
- exopthalmos/proptosis
What are the levels of TSH and T3/T4 in hyperthyroidism?
- decreased TSH
- increased T3/T4
What are the tx options for hyperthyroidism?
- anti-thyroid drugs (ATD)
- radioactive iodine (RAI)
- lithium
- potassium iodide
- surgery
- symptomatic tx (i.e. beta blockers)
What is the preferred ATD class for hyperthyroidism?
- thioamides
What are the drugs of the thioamides?
- methimazole
- PTU
Define euthyroid
- normal thyroid levels
- asymptomatic
What is the MOA of thioamides?
- inhibit T3/T4 synthesis
- depletes stored hormone
- PTU only: inhibits peripheral conversion of T4 to T3 w/in hrs of dose
Why don’t pregnant women take methimazole?
- crosses placenta
- increases TSH and decreases T4 in fetus
What and when is the medication changed for preggers?
- PTU in 1st trimester –> switched to methimazole in 2nd
Discuss PTU v. methimazole for breastfeeding
- PTU OK but methimazole preferred
What are common ADEs for thioamides?
- GI upset
- arthralgia
- rash, urticaria, pruritis (more in methimazole than PTU)
What are the serious ADEs of thioamides?
- agranylocytosis
- hepatotoxicity
What is the monitoring schedule of free T4 for thioamides?
- 4w s/p initiating tx
- q 4-8w until euthyroid then q 2-3m
- once in remission, q 6-12m x 12-18m
What is the monitoring schedule of WBC for thioamides?
- onset of febrile illness of pharyngitis
What is the monitoring schedule of LFTs for thioamides?
- pts on pTU w/ S&S of hepatotoxicity
What is the MOA of iodides?
- inhibits prestored T3/T4 release
- decrease T3/T4 synthesis
- decrease thyroid gland vascularity
When are iodides used?
- thyrotoxicosis
What are the iodide products?
- potassium iodide (KI)
i. e. saturated sol (SSKI) & lugols
What are the ADEs of iodides?
- rash
- GI upset
- paresthesia
- immune hypersensitivity reaction
- salivary gland swelling
- iodism (iodine overdose)
When is lithium indicated?
- psych patients
- as an adjunct to thioamides
- not recommended in the guidelines
What is the MOA of Li?
- blocks T3/T4 relase
What is the dose of Li?
- 300mg q8h
What are the ADEs of Li?
- tremor
- polyuria
- renal failure
- seizure
- arrhythmia
- bradycardia
- suicide
- toxicity
When are beta blockers used in thyroid dzs?
- symptomatic tx of palpations, tachycardia, tremor, heat intolerance
What is the MOA of beta blockers?
- blocks b-adrenergic receptors to mitigate adrenergic symptoms
What are the ADEs of beta blockers?
- fluid retention
- bradycardia/heart block
- hypotension
- fatigue
What is an example of RAI?
- I131 (sodium iodide 131)
What is the MOA of RAI?
- taken up by thyroid via TSH receptor
- incorporated into stored hormone
- emits beta particles which irreversibly damage thyrocytes ==> hypothyroidism
What are the ADEs of RAI?
- dysphagia
- thyroid tenderness
Discuss T3/T4 monitoring on RAIs
- 2-4w s/p tx
When does hypothyroidism present on RAIs?
- 4-8w s/p tx
What will labs look like for subclinical hyperthyroidism?
- low TSH
- T3/T4 WNL
What is the tx for amiodarone induced thyroiditis Type I? Type II?
- type I: thiamides
- type II: glucocorticoids
What will labs look like for subclinical hypothyroidism?
- elevated TSH
- T3/T4 WNL
What will labs look like for hypothyroidism?
- increased TSH
- decreased T3/T4
What is the 1st line tx for hypothyroidism?
- synthetic levothyroxine
What is the MOA of L-thyroxine?
- increases T3/T4 levels
What is the dosing of L-thyroxine?
- initial = 1.6 mcg/kg/d
- adjustments = 12.5-25mcg/d
How is levothyroxine serum levels decreased?
- drugs that decrease absorption
- drugs that increase elimination
- age
- extreme obesity
- GI disorders
When are patients monitored who are on levothyroxine?
- 4-6w s/p intial tx
- once normalized, q 6-12m
What are the ADEs of synthetic thyroids?
- allergic reactions
- arrhythmia
- acute MI
- infertility
- wt loss
- heat intolerance
- increased fx risk
What are the synthetic thyroid hormones?
- levothyroxine
- liothyronine
- liotrix
What are the natural thyroid hormones?
- thyroid USP
- thyroglobulin USP
When are pregnant women being txed for hypothyroidism tested?
- q 4w during 1st half of pregnancy
What is a major concern of drug-drug interactions for pts on thyroid replacement therapy?
- warfarin
