Desiccated thyroid hormone , Armour thyroid and Thyroid USP is listed as obsolete by the FDA but continues to be prescribed and used by some people . I recently saw a video promoting the use of desiccated thyroid which prompted me to write this note.
Our thyroid gland produces thyroid hormone in a response to TSH ( thyroid stimulating hormone ) from our pituitary gland. The primary form of thyroid hormone produced and released into our blood is T4 . This T4 is slowly converted to the active hormone T3 in our tissues,primarily the liver . The T3 Hormone in correct amounts helps keep all of the cells of our body running at peak efficiency.
A deficiency of T4 and T3 results in a slow down of all of the machinery in our body and an excess of T4 and T3 can have toxic effects especially for our heart causing arrhythmia , heart failure , angina or even cardiac arrest. The effect of excess T3 is a concern for anyone with heart disease.
( many of us have a little silent coronary heart disease ).
So, why is desiccated thyroid hormone not a recommended treatment for hypothyroidism ?
Desiccated Thyroid Hormone is of animal thyroid tissue origin. This means that it contains a mixture of T4 and T3. The T3 is almost 100% absorbed rapidly producing abnormally high levels of T3 in the blood stream and potentially a toxic effect on that persons heart.
Levothyroxine ( L-thyroxine , levothyroid , synthyroid and others) is T4 and is much safer to use. The T4 is absorbed and converted slowly to the active T3 , similar to the function of a normal thyroid gland. Be safe . If you need thyroid hormone replacement, use T4.