Thyroid Flashcards
Thyroid Disorders- goals
goals: minimize or eliminate symp-> improve quality of life
- minimize long term damage to organs
–Hypothyroidism
-myxedema come
-heart disease
–Hyperthyroidism
-heart disease
-arrhythmias
-sudden cardiac death
-bone demineralization and fractures
Normalize free T4 and TSH conc
Hypo vs hyperthyroidism
know this picture
Hypothyroidism overview
IODINE DEFICIENCY MC CAUSE
1. Hashimoto disease- mc hypo w/ iodine sufficiency
2. Iatogenic - thyroid resection or radioiodine ablatve therapy
3.Secondary causes
-pituitary insuff-failure to produce adequate TSH secretion
-drug induced
Thyroid hormone replacement= ae (star)
cardiovasc- tachy, angina, dysrhythmia, htn
cns- insomnia, tremors, ha, anxiety
GI- Nausea, diarrhea, cramps
Other: menstrual irreg, weight loss, sweating, heat intolerance, fever
Thyroid hormone replacement- general principles
- Antacids, calcium, cholestyramine, estrogen, iron, phenytoin-> Decrease levothyroxine effects
- Warfarin- increases warfarin effect
- Amiodarone- increase or decrease thyroid production
Contraind: 1. RECENT MI 2. ADRENAL INSUFF 3. HYPERTHYROIDISM
Levothyroxine
Synthetic T4
Brands: Synthroid, Levoxyl, Tirosint
brand only no generic bc branding has less variation
pts need consistently from same manufacturer to prevent variations
Levothyroxine dosing
lower dose in Cardiovascular dz
higher dose in pregnancy
USUALLY DOSED IN MORNING ON EMPTY STOMACH 30-60 MIN B4 BREAKFAST OR @ BEDTIME 4 HOURS AFTER LAST MEAL
- DOSED SEPARATELY FROM OTHER MEDS BC EFFECTS
Special about levothyroxine?
Color coded by mg dosing
Levothyroxine- monitoring, AE
Monitoring:
-TSH 4-6 wks after initiating or changing therapy
-use free T4 rather than TSH if CENTRAL OR SECONDARY HYPOTHYROIDISM bc gets away from feedback mech
AE- Hyperthyroidism & cardiac abnormalities
bioequivalency- changing from brand to genereic is discouraged
Hypothyroidism- M
TSH high= give high dose bc sign of not enough T4
Other meds not recommended
- Liothyronine- synthetic T3
- Liotrix - synth T4/T3
- Dessicated thyroid
NO THYROID MEDICATION SHOULD EVER BE USED FOR WEIGHT LOSS
Hypothyroidism pharmacotherapy
untx or inadequately tx hypthyroidism CAN NEGATIVELY IMPACT SURGICAL OUTCOMES
Preparing for surgery? depends on how long NPO
symptomatic therapy? check TSH to determine if dx appropriate
may be able to lower or stop levothyroxine dose
Management of hyperthyroidism
- Graves disease
-Beta Blocker
-Thionamides-> Methimazole & Propothiouracil
-Iodinated contrast agents
-Lithium carbonate
-Radioactive iodide - Toxic Nodular Goiter
-Beta blocker + thionamide - Hyperthyroidism from Thyroiditis
-Beta blocker
-Ipodate sodium or iopanoic acid-> corrects elevated T3 levels and is continued for 15-60 days until the serum FT4 level normalizes
-THIONAMIDES ARE INEFFECTIVE-> THYROID HORMONE PRODUCTION IS ACTUALLY LOW
-MONITOR FOR HYPOTHYROIDISM-> TX W/ LEVOTHYROXINE
Beta- blockers
Metoprolol, atenolol (selective), and propranolol (non selective)
MOA: blocks many hyperthyroidism manifestations mediated by Beta adrenergic receptors-> MAY BLOCK (LESS ACTIVE) T4 CONVERSION TO (MORE ACTIVE) T3
ae and warnings: Review from prior lectures-> Brady, ED
Efficacy:
-primarily for SYMPTOMATIC RELIEF
-OFF LABEL
Atenolol preferred:
Good candidates:
-Elderly
-heart rate over 90
- hx of CVD
-all pts experiencing symptoms
Alternatives to Beta blockers:
-clonidine
-nondihydropyridine calcium channel blocker
Thionamides
MOA: inhibits iodination and synthesis of thyroid homrones-> PTU may block t4/t3 conversion in the periphery as well
slow onset in reducing symp-> max effect 4-6 months
AE: HEPATOTOXICITY RISK W/ PTU (BOXED WARNING)-> OBTAIN BASELINE LFT, rash, arthralgias, fever, agranulocytosis early in therapy
1. Methimazole- preferred
2. Propylthiouracil (PTU)- 1st line prior to or during 1st trimerster
tx: usually lasts 1-2 years
