Pharmacotherapy: Thyroid Disorders Flashcards
1
Q
Normal Thyroid Values
A
- Total T4: 4.6-12 mcg/dL
- Free T4: 0.7-1.9 ng/dL
- Total T3: 80-180 ng/dL
- TSH: 0.4-4 mIU/L
2
Q
Hypothyroid Values Compared to Normal
A
- ALL low except TSH
- TSH is elevated
3
Q
Hyperthyroid
A
- All elevated except TSH
- TSH is low
4
Q
Hypothyroidism
A
- Deficiency of thyroid hormone defined as either primary or secondary
- Primary: thyroid gland failure. Hashimoto’s disease, iodine deficiency, goitrogens
- Secondary: pituitary disease, hypothalamic disease
5
Q
Hypothyroidism Symptoms
A
- Asymptomatic to coma
- Dry skin
- cold intolerance
- Decreased appetite
- Weight gain
- Constipation
- Weakness
- Lethargy/fatigue
- Mental impairment
- Depression
- Myalgia/muscle cramps
- Stiffness
- Menstrual irregularities
6
Q
Hypothyroidism Signs
A
- Weakness
- Coarse skin
- Cold or dry skin
- Periorbital puffiness
- Bradycardia
- Speech slowed
- Hoarseness
- Hyporeflexia
7
Q
Hypothyroidism: CV Effects
A
- Systolic dysfunction
- Reduced stress tolerance
- Cardiac autonomic dysfunction
- Reduced oxygen uptake
- Diastolic hypertension
- Increases arterial stiffness
- Insulin resistance
- Pro-atherosclerotic profile
- Pro-coagulative pattern
8
Q
Hypothyroidism Treatment
A
- Levothyroxine (LT4) = drug of choice
- Bioavailability differences can exist between patients, so the same LT4 product should be maintained
- Liothyronine (synthetic T3) - IV or PO, rapid absorption
- Liotrix (synthetic T4 and T3)
- Natural Hormones: dessicated thyroid extract from beef/pork thyroid gland
9
Q
LT4 Dosing
A
- Depends on age/cardiac disease history
- <50 y.o.: initial dose 50 mcg and increased to 100mcg/day after about 4 weeks
- Patients >50 y.o. OR with known cardiac disease: initial dose 25 mcg, titrate up by 12.5-25 mcg as needed every 4 weeks
10
Q
Myxedema Coma
A
- End-stage hypothyroidism
- Initial therapy: IV bolus levothyroxine 300-500 mcg and IV hydrocortisone 100mg q8h
- Follow by IV levothyroxine 75-100 mcg until patient stabilizes and oral meds begun
11
Q
Hypothyroidism Special Populations
A
- Pregnancy: associated with increased risk of still births
- Congenital deficiency associated with decreased physical/mental activity, CV, GI, and neuromuscular function
- Infants born with hypothyroidism require replacement to prevent cretinism
12
Q
T4/T3 Controversy
A
- Synthetic T4 preferred by most physicians and considered drug of choice
- Some patient complained of worsening symptoms and then switched to T4 from other formulations including DTE and thus prefer other formulations
13
Q
Drug Induced Thyroid Disease
A
- Lithium: up to 50% develop hypothyroidism, goiter, or hyperthyroidism (less common) likely due to hormone synthesis/secretion inhibition
- Treat with LT4, removal of lithium may not reverse these symptoms
14
Q
Hypothyroidism DIs
A
May have to increase the doses of the following:
- Calcium
- Iron
- Prenatal
- Vitamins
- Fiber
- Soy
- Orlistat
- Sevelamer
- Sodium Polystyrene
- Sucralfate
May Increase Thyroid Hormone Elimination:
- Rifampin
- Carbamazepine
- Phenytoin
- Phenobarbital
15
Q
Hyperthyroidism
A
- Increased T4, T3, or both
- Grave’s Disaese: autoimmune syndrome, more common in women, antibodies act similarly to TSH and cause hormone release. Can diagnose by detecting TSHR-SAb
