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
16
Q
Other Hyperthyroidism Causes
A
- Toxic Thyroid nodules
- Multinodular goiter
- Excess hormone intake
- Pregnancy
17
Q
Hyperthyroidism Symptoms
A
- Nervousness
- Anxiety
- Palpitations
- Emotional lability
- Fatigability
- Heat intolerance
- Increased appetite
- Weight Loss
18
Q
Hyperthyroidism Signs
A
- Warm
- Moist skin
- Pretibial myxedema
- Thin hair
- Lid lag
- Tachycardia
- Gynecomastia in men
- Hyperactive deep tendon reflex
- Fine tremor
- Thyromegaly
19
Q
Beta-Blockers + Hyperthyroidism
A
- Nonselective agents are preferred since they reduce palpitations, tremor, anxiety, and heat intolerance
- May also impair the conversion of T4 to T3
- Dose: 80-160 mg/day over 4 doses
- Symptomatic relief, not direct effect on thyroid hormones
20
Q
Pharmacological Treatment of Hyperthyroid - Iodides
A
- Iodides: block production and release thyroid hormone, used preoperatively for thyroidectomy and for reducing hormone release in thyroid storm
- Potassium iodide saturated solution (SSKI) - 38 mg iodide per drop
- Potassium iodide as Lugol’s solution 6.3 mg iodide per drop
21
Q
Pharmacological Treatment of Hyperthyroid - PTU/MMI
A
- Propylthiouracil and methimazole
- Block thyroid hormone synthesis
- PTU also inhibits the conversion of T4 to T3
- PTU: 300-600 mg per day over 3-4 doses
- MMI: 15-30 mg per day
22
Q
PTU/MMI Adverse Effects
A
- Generally low
- PTU: can cause hepatic necrosis
- MMO: cholestatic jaundice
- Agranulocytosis is the most serious, can occur suddenly, especially within the first 3 months of treatment and can cause sepsis
23
Q
Thyroidectomy
A
For patients with large glands who can’t tolerate or don’t respond to other therapies
24
Q
Radioactive Iodine
A
- RAI
- Used to destroy overactive thyroid cells
25
Q
Hyperthyroidism Special Populations
A
- Thyroid Storm: medical emergency of severe thyrotoxicosis usually precipitated by infection, trauma, surgery, RAI treatment, or withdrawal from antithyroid medications
- Pregnancy: usually caused by Grave’s disease. Beta-hCG has TSH agonist activity which can worsen or precipitate thyrotoxicosis
26
Q
Thyroid Storm Treatment
A
- Shorting acting beta blocker or iodide AND
- PTU at 900-1200 mg AND
- Hydrocortisone 100 mg IV q8h for assumed adrenal insufficiency
27
Q
Hyperthyroidism + Pregnancy Treatment
A
- PTU is the treatment of choice
- If untreated, spontaneous abortion, premature delivery, low birth weight, and eclampsia can occur
