In recent years, research has advanced in the area of local control of thyroid activity and metabolism, including thyroid hormone membrane transport and deiodinase activity. Thyroid hormone replacement in certain conditions despite having normal TSH levels has shown significant clinical benefits. Research has also shown the superior benefits of T3 replacement instead of the standard T4 thyroid hormone replacement therapy.
Thyroid replacement therapy is one of the key areas in compounding pharmacy, where customized solutions are delivering benefit to many patients. American Integrative Pharmacy provides compounded thyroid hormone replacement therapies to patients in Long Beach, Torrance, Los Angeles, South Bay Orange County, Southern California areas and nationwide.
Assessing Thyroid Function
For the correct assessment of thyroid function, it is important to understand that deiodinase enzymes are vital control points of cellular thyroid activity. They determine intracellular activation and deactivation of thyroid hormones. Three different deiodinase enzymes present in different tissues mediate this local control of cellular thyroid levels.
Type I deiodinase (D1) and type II deiodinase (D2) promote cellular thyroid activity through the conversion of inactive thyroxine (T4) to the active triiodothyronine (T3). On the other hand, type III deiodinase (D3) diminishes cellular thyroid activity through the conversion of T4 to the anti-thyroid reverse T3.
Each type of deiodinase enzyme acts according to the change in physiologic conditions. This local control of intracellular T3 and T4 levels leads to different tissue levels of T3 and T4 under varying conditions. The activity of these deiodinases and the transport of T3 and T4 into the cell determine the cellular and tissue thyroid levels and not serum thyroid levels. Therefore, serum thyroid levels may not necessarily predict tissue thyroid levels under different physiologic conditions.
Deiodinase Type I (D1)
While D1 is responsible for the conversion of inactive T4 to active T3 throughout the body, but it is not a key determinant of pituitary T4 to T3 conversion, which is controlled by D2. D1 but not D2 is down-regulated and suppressed due to emotional and physiologic stress, dieting, depression, weight gain, insulin resistance, diabetes, obesity, inflammation from systemic illness or autoimmune disease, chronic pain, chronic fatigue syndrome and fibromyalgia, and exposure to plastics and toxins.
D1 activity is also reduced in females, which makes women more prone to tissue hypothyroidism. This condition can result in fatigue, chronic fatigue syndrome, depression, fibromyalgia, and obesity despite having normal TSH levels.
Deiodinase Type II (D2)
Thyroid stimulating hormone (TSH) is produced in the pituitary and is regulated by T3 levels. Pituitary is different than all other tissues in the body, which means that the T3 levels in the pituitary may not directly correlate with that of other tissues in the body under different physiologic conditions.
Deiodinases have a unique make up in the pituitary, which enables them to respond differently and often opposite to that of every other tissue in the body. Several conditions lead to a growth in pituitary T3 levels, which suppressing cellular T3 levels in the rest of the body at the same time. That makes pituitary and the TSH an inferior indicator for tissue thyroid levels in the rest of the body under varying physiologic conditions.
AIP offers a wide range of services, including online prescription refills, to patients in Long Beach, Torrance, Los Angeles, South Bay Orange County, Southern California areas and nationwide.
American Integrative Pharmacy is located in Lomita, CA serving residents in and around Orange County, Los Angeles, Long Beach, Torrance and surrounding areas. Online prescription sales are available across the US.