As my first blog on Thyroid Answers explained, our thyroid gland makes two active forms of thyroid hormone. The first difference between these forms, T4 and T3, lies in how many iodine atoms are attached to the backbone structure. As you might guess, T4 has 4 iodines and T3 has 3 iodines. They are added to a backbone made out of two bonded amino acids, both of them tyrosines.
The second difference lies in how strong of a reaction these hormones trigger in the tissues of our body. The primary function of the thyroid hormones is to control the gas pedal of metabolism. While the prior blog goes into more detail, the point here is that T3 puts a stronger pressure on the gas pedal: it may be 100 times more potent. In other words, one drop of T3 equals 100 drops of T4.
The final difference lies in the half lives of T4 and T3. A half life measures the amount of time required for a chemical substance’s concentration to drop in half without further production. A half life of 1 hour would mean that after 1 hour, ½ of the original substance would be metabolized and ineffective. T4 has a half life of 7 to 10 days while T3 has a half life of 4 to 6 hours.
Why would you produce a weak, yet long acting form and a stronger, yet short acting form? You could say that God knew a system where the slow to change weaker form, T4, is then changed into the shorter acting, stronger form, T3, over time would prevent sudden fluctuations that might cause adverse effects.
The challenge for health care providers arises when we are trying to supply the right dose for patients after their system has gone haywire. Conventional medicine believes that supplying T4 in the pharmaceutical versions takes care of the issue, and T3 is not needed. They believe the body will convert enoughT4 into T3 on its own. For many patients they are correct.
The problem arises when some patients are not able to convert T4 into T3 adequately. Their pituitaries think they have enough T4, but in reality their bodies would benefit from more T3 that the tissues can’t get. For those patients, administering T3 or T4 plus T3 serves to alleviate their hypothyroid symptoms much more effectively.
Helping patients live healthier more abundant lives with thyroid conditions requires several things: we must understand the science; we must recognize the uniqueness of each patient’s metabolism; and we must treat each patient as individuals to whom we apply evidence-based principles. Return for the next article on the different therapies we offer hypothyroid patients.
Sanctuary Functional Medicine, under the direction of Dr Eric Potter, IFMCP MD, provides functional medicine services to Nashville, Middle Tennessee and beyond. We frequently treat patients from Kentucky, Alabama, Mississippi, Georgia, Ohio, Indiana, and more... offering the hope of healthier more abundant lives to those with chronic illness.