Desiccated Thyroid (DT) is a prescription medication used to treat hypothyroidism, a condition where the thyroid gland does not produce sufficient hormones to regulate the body’s metabolism. This treatment method has a long history, predating the development of synthetic hormone options available today. The goal of taking desiccated thyroid is to restore normal hormone levels, thereby alleviating symptoms associated with an underactive thyroid, such as fatigue, weight gain, and cold intolerance.
The Source and Processing of Desiccated Thyroid
The name “desiccated thyroid” describes its physical state and origin. The raw material is sourced from the thyroid glands of pigs, which is why it is sometimes referred to as porcine thyroid. These glands are collected from animals used for food and undergo preparation to make them suitable for human consumption.
The collected glands are cleaned and then subjected to desiccation, the process of drying the tissue. This drying removes all moisture and concentrates the thyroid material into a stable form. The dried tissue is finely ground into a powder, which is combined with inactive ingredients, such as binders and fillers, to be pressed into tablets.
This manufacturing method aims to preserve the full spectrum of compounds naturally present in the porcine thyroid gland. While the final product is standardized based on its hormone content, the animal-derived nature results in a complex substance containing more than just the primary thyroid hormones.
Hormonal Components and Therapeutic Action
The therapeutic action of Desiccated Thyroid is linked to the specific hormones it contains, which are structurally identical to those produced by the human thyroid gland. DT provides a combination of all four major thyroid hormones: Thyroxine (T4), Triiodothyronine (T3), and smaller amounts of monoiodothyronine (T1) and diiodothyronine (T2). These hormones function as a replacement for the body’s deficient supply, restoring metabolic function.
Thyroxine (T4) is the prohormone, meaning it is long-acting and acts as a reservoir that must be converted into the active form by the body’s tissues. Triiodothyronine (T3) is the highly potent and metabolically active hormone, providing a more immediate effect on body cells. Desiccated thyroid typically contains a ratio of T4 to T3 that is approximately 4-to-1.
This fixed ratio differs from the proportion produced by the human thyroid, which secretes T4 and T3 at a ratio closer to 14-to-1. By supplying both the long-acting T4 and the readily available T3, DT ensures the body receives the necessary raw materials to regulate cellular energy expenditure, body temperature, and overall metabolic rate. The inclusion of T2 and T1, while less understood, adds to the idea of a comprehensive replacement therapy.
Distinction from Synthetic Hormone Replacement
The most significant difference between Desiccated Thyroid and synthetic treatments like levothyroxine lies in their hormonal composition. Levothyroxine is a pure, laboratory-made version of T4 only. The body is then expected to convert this inactive T4 into the active T3 hormone as needed.
Desiccated thyroid, however, offers a complete spectrum of thyroid hormones, including a direct dose of active T3. This characteristic is a primary reason why some individuals and practitioners prefer DT, especially if a patient’s body does not efficiently convert T4 into T3.
The composition of DT is closer to what a naturally functioning thyroid gland produces, though it comes in a fixed, standardized dose. This fixed ratio contrasts with the body’s natural ability to dynamically adjust T3 production from T4 based on moment-to-moment needs. Furthermore, DT’s use predates the modern regulatory process, meaning that while it is a prescription drug, many of its formulations have not undergone the safety and efficacy evaluation required for new medications by the U.S. Food and Drug Administration (FDA).
Administration and Safety Considerations
Desiccated thyroid is typically measured in “grains” for dosing, with one grain historically representing about 60 to 65 milligrams of the dried powder. Starting doses are generally low, particularly for patients with a long history of severe hypothyroidism or existing heart conditions. The dosage is carefully increased over several weeks until symptoms improve and blood work shows the desired hormone levels.
Regular blood monitoring is necessary to ensure the dose is appropriate and safe, which involves testing for Thyroid-Stimulating Hormone (TSH), Free T4, and Free T3 levels. The TSH level serves as the primary indicator of whether the thyroid hormone replacement is adequate. An excessive dose can lead to symptoms of hyperthyroidism, such as nervousness, weight loss, heat intolerance, and potentially dangerous heart rhythm abnormalities.
A concern with DT is the potential for batch-to-batch variability in hormone content due to its natural, animal-derived source, which can make consistent dosing a challenge. Because of the higher amount of T3 in DT compared to the human gland, patients may experience transient elevations of T3 in the blood after taking the medication. Patients with underlying heart disease should be monitored closely, as the rapid action of T3 can increase the risk of adverse cardiovascular events.