Term
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Definition
1. Restore euthyroid state.
2. Reverse clinical manifestations of hypothyroidism.
3. Reduce the size of goiter in Hashimoto’s thyroiditis. |
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Term
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Definition
T4
• Brand names: Levothroid®, Levoxyl®, Synthroid®, Unithroid®, etc.
• Drug of choice
• MOA: prohormone that becomes deiodinated in peripheral tissues to form T3
• Dose:
• Young, healthy patients: 1.6 mcg/kg/day (based on IBW for obese patients)
• Typical: females: 75-112 mcg/day, males; 125-200 mcg/day
• Elderly: 25-50 mcg/day
• IV = 50% of oral dose, IM = 80% of oral dose
• Controversy regarding bioequivalence among formulations and subtle differences
in bioavailability
• Monitoring
• Re-evaluate TSH after six weeks and ↑ dose in 12-25 mcg/day increments
• If symptoms persist, may repeat TSH in three weeks
• Periodic monitoring after goal is achieved |
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Term
| Levothyroxine dose adjustments |
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Definition
Increase:
• Pregnancy
• GI disorders/impaired acid secretion
• Nephrotic syndrome
• Treatment with rifampin, carbamazepine, phenytoin, or phenobarbital
• Decrease:
• Geriatrics
• After pregnancy
• Weight loss
• Treatment with androgens |
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Term
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Definition
May be considered in patients remaining symptomatic despite T4
replacement and normal TSH
• T3 combinations demonstrate a wide variation in serum T3
concentrations throughout the day
• Short t1/2 (~24 hours) and rapid GI absorption
• T4 levels remain low although TSH may reflect adequate
therapy, causing inappropriate dose changes |
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Term
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Definition
synthetic T3
Brand names: Cytomel®, Triostat®
• Place in therapy:
• Not recommended for initial therapy
• Patients remaining symptomatic despite T4 replacement and normal TSH or
preparation for thyroid scan in patients with thyroid cancer
• MOA: exact mechanism unknown; several metabolic effects including
metabolism, growth, and development
• Dose:
• Young, healthy patients: 25 mcg/day; max. 100 mcg/day (usual: 25-75 mcg/day)
• Elderly: 5 mcg/day
• Monitoring
• Re-evaluate TSH and T3 every one to two weeks and ↑ dose by 12.5-25 mcg/day
• Geriatrics: ↑ by 5 mcg/day every two weeks
• Adverse reactions: higher incidence of CV side effects |
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Term
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Definition
Synthetic T4+T3 Combination
• Brand names: Thyrolar® (T4:T3 = 4:1)
• Place in therapy: offers no therapeutic advantage despite high cost
• Formulations:
• Thyrolar®: 1/4 [levothyroxine sodium 12.5 mcg and liothyronine sodium 3.1 mcg]
• Thyrolar®: 1/2 [levothyroxine sodium 25 mcg and liothyronine sodium 6.25 mcg]
• Thyrolar®: 1 [levothyroxine sodium 50 mcg and liothyronine sodium 12.5 mcg]
• Thyrolar®: 2 [levothyroxine sodium 100 mcg and liothyronine sodium 25 mcg]
• Thyrolar®: 3 [levothyroxine sodium 150 mcg and liothyronine sodium 37.5 mcg]
• Dose:
• Young, healthy patients: levothyroxine 25 mcg/liothyronine 6.25 mcg daily
(usual: levothyroxine 50-100 mcg/liothyronine 12.5-25 mcg/day)
• Elderly: levothyroxine 12.5-25 mcg/liothyronine 3.1-6.25 mcg daily
• Monitoring
• Re-evaluate TSH and T4 every two-three weeks and ↑ dose
by 12.5mcg/3.1 mcg increments |
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Term
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Definition
T4+T3 Combination
• Brand names: Armour Thyroid®
• Dessicated thyroid of pigs, sheep, or beef and standardized by I- content
• Place in therapy: not recommended
• Formulations: 15, 30, 60, 90, 120, 180, 240, 300 mg (1 grain~60 mg)
• Dose:
• Young, healthy patients: 15-30 mg (usual: 60-120 mcg/day)
• Elderly: not recommended due to CV risk and availability of safer
alternatives
• Monitoring
• Re-evaluate TSH and T4 every two to three weeks and ↑ dose by 15 mg
increments |
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Term
Dosage Conversions
Dessicated thyroid T4 |
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Definition
1 grain thyroid extract = 100 mcg T4
• Example: 1 ½ grains dessicated thyroid (90 mg) = 150 mcg T4 |
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Term
Dosage Conversions
T4-T3 combination T4 |
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Definition
Calculate based upon the amount of T4 and T3 in the preparation
• T4:T3 = 4:1
• Example: levothyroxine 50 mcg and liothyronine 12.5 mcg
T4 50 mcg and T3 12.5 mcg
50 + (4*12.5) = 100 mcg of T4 |
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Term
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Definition
Long lasting hypothyroidism +
Acute event
• Infection
• Trauma or MI
• Cold exposure
• Administration of hypnotics or sedatives |
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Term
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Definition
Thyroid hormone
• Controversy regarding preferred regimen
• Levothyroxine 200 – 400 mcg IV LD, then 1.6 mcg/kg/day IV thereafter
• Liothyronine 5-20 mcg IV, followed by 2.5-10 mcg q8h
• Both T4 and T3 doses may be reduced in patients with cardiovascular
disease
• Glucorticoids
• Stress doses of GCs should be used until coexisting adrenal insufficiency
can be ruled out
• Hydrocortisone 100 mg IV q8h
• Supportive therapy
• Mechanical ventilation if necessary
• IVF including electrolytes and glucose
• Correction of hypothermia
• Treatment of underlying infections with empiric antibiotics |
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Term
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Definition
1. Eliminate excess thyroid hormone.
2. Minimize symptoms.
3. Reduce the likelihood of long-term consequences. |
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Term
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Definition
• Place in therapy:
• Drug of choice for mild hyperthyroidism and minimal thyroid enlargement
• Short term as preparation for ablative radiotherapy or surgery
• Goal: attain euthyroid state in three to eight weeks followed by ablative
surgery (radioiodine or surgery) or continuation with hope for remission
• Symptoms improvement after 4-8 weeks
• Baseline labs
• CBC with differential
• Contraindicated in ANC < 5000 mm3
• Liver profile
• Contraindicated in elevated liver transaminases |
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Term
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Definition
• Tapazole®
• Drug of choice in non-pregnant women and less side effects
• MOA: inhibits thyroid hormone synthesis by blocking oxidation of I- in
thyroid gland (inhibits formation of T3)
• Does not inactivate circulating T4 and T3
• Dose
• Hyperthyroidism:
• Mild: 15 mg/day in three divided doses
• Moderate: 30-40 mg/day in three divided doses
• Severe: 60 mg/day in three divided doses
• Maintenance: 5-15 mg/day (may be given as single daily dose)
• Grave’s disease: 10-20 mg once daily
• Maintenance: 5-10 mg once daily x 12-18 months, then taper or D/C if TSH normalizes
• Available in 5 and 10 mg tablets
• Monitoring: TSH, T4, T3, CBC w/ diff, LFTs, PT/PTT |
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Term
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Definition
• Propyl-Thyracil®
• Drug of choice in first trimester of pregnancy and in thyroid storm
• MOA: inhibits thyroid hormone synthesis by blocking oxidation of Iin
thyroid gland (inhibits formation of T4 and T3)
• Inactivates circulating T4 and T3
• Dose
• Hyperthyroidism:
• Initial: 300 mg/day in three divided doses
• Severe or large goiter: 400 mg/day in three divided doses
• Maintenance: 100-150 mg/day (may be given as single daily dose)
• Grave’s disease: 50-150 mg TID to restore euthyroidism
• Maintenance: 50 mg BID-TID x 12-18 months, then taper or D/C if TSH
normalizes
• Available in 50 mg tablets
• Monitoring: TSH, T4, T3, CBC w/ diff, LFTs, PT/PTT |
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Term
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Definition
• Formulations:
• Lugol’s solution ® (potassium iodide-iodine) – 6.3 mg I-/drop
• SSKI ® (potassium iodide solution) – 38 mg KI-/drop
• Place in therapy: severe hyperthyroidism or allergy to
thionamides
• MOA: inhibits I- organification in the thyroid gland for use
(Wolff-Chaikoff effect) inhibits thyroid hormone synthesis
• Inhibits hormone secretion within 1-2 days
• Symptomatic improvement in 2-7 days
• Maximum effect after 10 days |
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Term
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Definition
• Pre-op prep for thyroidectomy in Grave’s disease: 3-5 drops po TID
• Thyroid storm: 10 drops po TID |
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Term
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Definition
Pre-op prep for thyroidectomy in Grave’s disease: 1-5 drops po TID
• Thyroid storm: 5 drops po QID
• Adjunctive therapy following radioiodine: 3 drops po BID |
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Term
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Definition
Place in therapy: ameliorate symptoms of tachycardia,
palpitations, anxiety, heat intolerance until euthyroid state is
achieved
• ↑ β-receptors in hyperthyroidism
• Some β-blockers slowly reduce T3 concentrations
• Propranolol, atenolol, metoprolol
• Should be started as soon as diagnosis is identified, unless
contraindicated
• Dosing:
• Atenolol 25-50 mg/day (up to 200 mg/day)
• Goal: pulse < 90 bpm |
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Term
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Definition
• Hicon®, Iodotope® (Sodium Iodide,131I)
• Place in therapy:
• Treatment of mild, well-tolerated hyperthyroidism
• In patients with underlying heart disease, elderly, or severe disease,
MUST pre-treat with thionamide
• MOA: active in thyroid gland necrosis/fibrosis and edema
• Contraindicated in pregnancy and lactation
• Caution: may worsen Grave’s opthalmopathy
• Dose administered orally as capsule or solution
• Result:
• Thyroid ablation within 6-18 weeks
• Lifelong therapy with T4 |
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Term
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Definition
• Rarely conducted
• Most invasive and most costly treatment
• Indications
• Obstructive or large goiter
• Toxic adenoma and multinodular goiter
• Ineffective or contraindicated drug therapy
• Ophthalmopathy
• Pregnant women allergic to anti-thyroid drugs
• Patients with allergies or poor compliance with treatment
• Pre-operative medications:
• Prevention of thyroid storm (may occur during surgery through
first 18 hours)
• Thionamide x 5-8 weeks pre-op (methimazole 10-15 mg po daily)
• Iodides x 10 days pre-op (KI-)
• β-blockers |
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