Desiccated thyroid, also known as thyroid extract, is thyroid gland that has been dried and powdered for medical use. It is used to treat hypothyroidism. It is less preferred than levothyroxine. It is taken by mouth. Maximal effects may take up to 3 weeks to occur.Side effects may occur from excessive doses. This may include weight loss, fever, headache, anxiety, trouble sleeping, arrythmias, and heart failure. Other side effects may include allergic reactions. Use in pregnancy and breastfeeding is generally safe. Regular blood tests are recommended to verify the appropriateness of the dose. They contain a mixture of thyroxine (T4) and triiodothyronine (T3).Desiccated thyroid has been used since the late 1800s. It is usually made from pigs, sheep, or cows. It is available as a generic medication. In 2017, it was the 130th most commonly prescribed medication in the United States, with more than five million prescriptions. Usage has decreased since the 1960s. Medical uses
The American Association of Clinical Endocrinologists and the Royal College of Physicians recommend against the use of thyroid extract for the treatment of hypothyroidism. Concerns include the potential for adverse effects from superphysiological levels of T3 and the absence of long-term safety data from randomized clinical trials. They recommend levothyroxine as the preferred treatment. Some practitioners refuse to use desiccated thyroid.About 65 mg of thyroid extract is equivalent to 100 μg of levothyroxine.Arguments against desiccated thyroid include:

Desiccated thyroid preparations have a greater variability from batch to batch than synthetic ones.
It was also discovered that even mild hyperthyroidism as defined by a suppressed TSH level, whether due to disease or overtreatment, was associated with poorer bone density in women, and with higher rates of atrial fibrillation in elderly patients. Names
This product is sometimes referred to as thyroid USP, thyroid BP. Brands differing only in binders and fillers. References
External links
"Thyroid tablets". Drug Information Portal. U.S. National Library of Medicine.