Synthroid is a hormonal thyroid medicine. It contains chemical levothyroxine sodium and is used when the thyroid gland does not produce enough hormones. It could also help decrease the size of enlarged thyroid glands (known as goiter) and to treat thyroid cancer.

Rare side effects might include severe headache in children, skin rash or hives.

Synthroid, the most-prescribed thyroid medication for the past 42 years, will remain available in all strengths to meet the needs of the millions of patients who rely on it every day. Its manufacturer, Abbott Laboratories, has submitted a new drug application (NDA) for Synthroid to the FDA and is confident it will be approved. If patients have questions about their thyroid medication, they should talk with their physician.