Synthroid, a trade name for levothyroxine, is a man-made supplement used to treat hypothyroidism. Hypothyroidism occurs when the thyroid gland, which helps to regulate all body functions, is functioning at less than normal levels. Hypothyroidism can hinder heart rate, body temperature, bowel regularity, digestion and efficient use of medications. Levothyroxine requires 4 to 6 weeks of use to achieve therapeutic levels, and side effects reflect too much or too little medication.
Heart Irregularities
DailyMed, a website from the National Library of Medicine, recommends not prescribing levothyroxine for patients with a history of cardiac problems. Levothyroxine may precipitate an increase in heart rate, palpitations, chest pain and an irregular heart rate for this group of patients. If levothyroxine is necessary, careful dosing and monitoring of the heart's response to the medication is required.
Weight Loss
Though weight loss is a side effect of this medication, according to DailyMed, using levothyroxine for weight loss in patients with a normally functioning thyroid causes hyperthyroidism, and may have life-threatening consequences. Hyperthyroidism occurs when the thyroid is functioning at a faster than normal level, which may harm vital organs.
Heat or Cold Intolerance
According to the website Rxmed, patients with hypothyroidism experience an intolerance to cold as a symptom, but when they use levothyroxine, this symptom is alleviated. Continuing cold intolerance or developing heat intolerance requires physician notification and a possible adjustment in the levothyroxine dose.
Fatigue
Fatigue, a symptom of hypothyroidism, responds to levothyroxine treatment, according to MayoClinic.com. If fatigue continues or worsens while taking levothyroxine, the dosage may need to be adjusted by the physician.
Hypersensitivity
Symptoms of hypersensitivity to the inactive ingredients in levothyroxine may cause a reaction in certain individuals, according to DailyMed. Notifying the physician of symptoms such as itching, rash, nausea, vomiting, wheezing, fever, and swelling in the face and neck is necessary to avoid an emergency situation. DailyMed indicates that no hypersensitivity to the active ingredient, levothyroxine, has occurred.
