Desiccated Thyroid, also known as Natural Desiccated Thyroid (NDT) or Armour Thyroid, is an endogenous hormone replacement derived from the dried thyroid glands of pigs. It belongs to the class of thyroid hormones and contains a combination of thyroxine (T4) and triiodothyronine (T3), along with other thyroid gland constituents. This compound is used to treat hypothyroidism by supplementing the body's natural thyroid hormone levels. Researchers have studied its composition and effects to understand its role in thyroid hormone replacement therapy. The primary physiological roles of Desiccated Thyroid include regulating metabolism, energy production, and protein synthesis. It is primarily used in research areas focusing on thyroid hormone replacement therapy, metabolic disorders, and endocrinology. Researchers have found that it can effectively manage symptoms of hypothyroidism, although its use compared to synthetic alternatives remains a topic of debate. The mechanism of action of Desiccated Thyroid involves binding to thyroid hormone receptors in the nucleus of cells, which then modulates gene expression and influences metabolic processes. This activation leads to increased basal metabolic rate, enhanced oxygen consumption, and heat production. The pharmacokinetic properties of Desiccated Thyroid are complex due to its combination of T4 and T3. The half-life of T4 is approximately 7 days, while T3 has a shorter half-life of about 1 day. Metabolism occurs primarily in the liver and kidneys, and the bioavailability of oral administration can vary. Clinically, Desiccated Thyroid is used for the treatment of hypothyroidism and is available by prescription. Its regulatory standing varies by country, with some regions preferring synthetic thyroid hormones due to standardization concerns. Researchers have observed that while it is effective, the variability in hormone content can pose challenges in clinical use.