Comprehensive Nursing Pharmacology Q 22
Which of the following adverse effects is associated with levothyroxine (Synthroid) therapy?
A. Hypotension
B. Bradycardia
C. Tachycardia
D. Constipation
Correct Answer: C. Tachycardia
Levothyroxine, especially in higher doses, can induce hyperthyroid-like symptoms including tachycardia. Adverse effects (frequency undefined) include: angina pectoris, tachycardia, palpitations, arrhythmias, myocardial infarction, dyspnea, anxiety, fatigue, headache, heat intolerance, insomnia, irritability, diaphoresis, skin rash, alopecia, goiter, weight loss, menstrual irregularities, abdominal cramps, diarrhea, emesis, reduced fertility, and decreased bone mineral density (a result of TSH suppression).
Option A: Hypotension would be a side effect of bradycardia. Thyroid hormone therapy decreases aortic stiffness, promoting decreased blood pressure in about 50 percent of these patients. Antihypertensive treatment further improves aortic elasticity and can decrease blood pressure among patients with hypertension and hypothyroidism whose blood pressure does not drop as thyroid function is normalized.
Option B: An agent that increases the basal metabolic rate would not be expected to induce a slow heart rate. in a hypothyroid state, diastolic blood pressure increases, pulse pressure narrows, and renin levels decrease. This results in diastolic hypertension that is often sodium sensitive. Erythropoietin secretion is increased by T3, which can explain the normochromic, normocytic anemia often found in hypothyroidism. Thyroid hormones also regulate pacemaker-related genes through transcription as well as the beta-adrenergic system in cardiomyocytes. As a result of these mechanisms, heart rate increases in the presence of thyroid hormones and decreases in hypothyroidism
Option D: Constipation is a symptom of hypothyroid disease. The thyroid gland can have a significant impact on the gastrointestinal system. A common misconception is that diet causes chronic digestive trouble and weight changes, but this may be an oversimplification. Thyroid conditions and their resultant symptoms are often complex and require ongoing treatment by an endocrinologist.