Synthroid (Levothyroxine) is a synthetic version of the thyroid hormone thyroxine, prescribed to treat conditions of the thyroid gland. Individuals taking Synthroid are warned they may expect to take this medication for the rest of their lives. Synthroid has a number of listed side effects, many of which are considered serious. Burning, or a sensation of heat, in the feet and/or hands, has been reported by a number of patients taking Synthroid.
The thyroid gland, located in the front of the throat, is one of the largest endocrine glands in the body, making hormones that regulate many functions of the body, including heart rate, blood pressure, and body temperature. Thyroid hormones are needed for the optimal functioning of all body cells. Malfunctions of the thyroid gland include hyperthyroidism, or overactivity of the thyroid gland, and hypothyroidism, or underactive thyroid. Medications such as Synthroid help to regulate the thyroid's production of hormones for healthy functioning of all the body's systems.
In people with hypothyroidism, Synthroid replaces or raises levels of thyroxine in the body to normal. In cases of hyperthyroidism, Synthroid is prescribed alongside drugs such as Tapazole to manage symptoms of a thyroid gland overproducing thyroid hormones. Since Synthroid is a synthetic form of thyroxine, the dosage prescribed should approximate normal production of this hormone. Blood tests can determine if the amount of Synthroid needs to be adjusted.
According to MedicineNet's overview of Synthroid and the thyroid conditions for which it is prescribed, the side effects of this medication spring from toxic levels of thyroxine and generally mimic the symptoms of hyperthyroidism. Side effects can affect all systems of the body. Some are life-threatening, such as difficulty breathing, cardiac arrhythmia, and seizures. More common symptoms include weight loss, nervousness, irritability, gastrointestinal problems, insomnia, excessive sweating, joint inflammation, sensitivity to heat and feelings of warmth in various parts of the body.
According to WrongDiagnosis.com's symptom lists, numerous diseases and syndromes, including thyroid conditions, can be associated with sensations of burning in the feet and legs. Although instances of burning feet have been reported by Synthroid users on medical forums such as AskAPatient and Medications.com, the symptom of burning feet has not been specifically listed as a side effect of this medication.
Since side-effects of Synthroid relate to high levels of thyroxine in the body and cause symptoms similar to those of hyperthyroidism, such as sensations of heat and changes in responses to heat and cold, it's important to consult your physician about your dosage. If adjusting the Synthroid prescription doesn't resolve the discomfort of burning feet, further investigation may be needed, since burning, redness or tingling in the feet can also be a symptom of many other conditions and diseases.