According to Dr. Podell:
"Many holistic, integrative and complementary alternative medicine physicians believe that many people are effectively hypothyroid (thyroid deficient) because they are unable to make the main active thyroid hormone - which is not T4 but the form found in Cytomel and Armour Thyroid, that is, T3."Why would you need T3 treatment? Dr. Podell has some theories. According to him, some people are deficient in selenium, zinc, Vitamin A and/or Vitamin D, which can impair T4 to T3 conversion. He identifies a number of factors he feels can block T3 formation or aggravate thyroid dysfunction, including acute illness, excess cortisol due to physical and emotional stress, anxiety and chronic depression, goitrogenic vegetables, and foods high in iodine.
Dr. Podell explains some of the key signs that tell integrative practitioners a patient may need treatment: classic hyothyroidism symptoms; low basal body temperature; slow ankle reflexes; TSH level above 3; low free T4 or free T3 tests; and high Reverse T3.
Overall, the article is a helpful look at the approach that innovative thyroid doctors are taking to diagnosing and treating thyroid conditions. Well worth a read, if this is a direction you're interested in pursuing.