Friday, July 31, 2015

Basic intro to T3, T4, FT3 and FT4 after thyroidectomy

T3 is the active thyroid hormone utilized in the body. T3 can be used directly essentially everywhere in the body.

T4 is a storage form of thyroid hormones. T4 cannot be used anywhere in the body at all, so it is considered inactive or storage. It can only be converted to an active hormone state (T3) before being used.

Some T3 is made by the thyroid; the rest is converted from T4 in places like the liver and kidneys before being circulated for use around the body, also in cells that convert T4 to T3 for their own use directly.

T3 is also in a prescription called cytomel or liothyronine, this is synthetic T3. Cytomel is often sold in 5 mcg (low amount) or 25 mcg (high amount) pill forms so it is difficult to titrate a long term dosage sometimes if you need to be on it. T3 is also in natural thyroid (NDT) prescriptions (from animals). There are 9 mcg of T3 in each grain of natural thyroid in USA. T3 has very rapid effects. It has a fairly short half life.

T4 is in a prescription called Levothyroxine, Synthroid, Tirosint and other names. These are the synthetic forms. It also is in natural thyroid prescriptions (from animals). In natural thyroid there are 38 mcg of T4 per grain of natural thyroid (NDT) in USA. T4 tends to change things slowly because it is converted to T3 before being used, and may take weeks to come out of the body and thus has a longer half life.

T3 is best measured by Free t3 which is a measure of how much T3 is available for use. This varies fairly widely over the day. A higher value means more is available. A low value and we generally do poorly at that point of the day where it is low.  There are other T3 measures other than the Free T3 form but they are not ideal. T3 labs don’t measure daytime levels well near time of taking medications based on experience, so Free t3 labs are fairly time sensitive. When Free t3 level is low, many of us experience severe hypo symptoms no matter what the TSH says. You can also experience too much T3 and get hyper symptoms so having an experienced physician handling prescriptions in the T3 or NDT area is ideal, unfortunately this is hard to find.

T4 is best measured using Free t4. When relatively high in some of us it excites a high level of hyper symptoms and I experience this fairly easily. I do poorly at high levels of Free t4. One can also be hypo or get hypo symptoms when the FT4 is quite low.

Two common problem areas and some symptoms often faced post TT

As thyroid cancer survivors, having no thyroid, we are fairly unique medically in that we can experience both an excess (hyper) and a deficiency (hypo) simultaneously.

HYPER (most common with a high FT4 post TT on high levels of T4, but can be from too high a FT3 too) symptoms include mood changes and swings, irritability or a short temper, headaches and migraines, anxiety, palpitations, shortness of breath and/or breathlessness, too fast a GI system and in some more on the constipation side, sleeplessness in some and in some the opposite or sleeping 12 or 15 hours at a time, body aches and pains like joint pains and shoulder issues, weight changes due to excess hunger with little or no satiety, lots of pre-migraine and migraine aura effects (can include thyroid ocular aura disorders -TOADs) even if you never get or have never had a migraine in your life.

HYPO (most common with low FT3 even if TSH suppressed) all the symptoms of hypothyroidism, but common are the brain fog, depression, loss of attention span (forgetting things), skin issues, hair loss, fingernail issues, feeling dog tired, Sleeping lots, slowing metabolic rate leading to inability to lose weight despite honest effort, medication sensitivities, irritable/sensitive GI, inability to do things like we used to, food intolerances, allergies, just can't focus on work or family, when very HYPO a differing kind of irritability and headache than the HYPER one. A very low Free T3 can also cause bradycardia, palpitations in some, and many types of cardiac issues are possible. Many more issues are common when HYPO and can be found on internet searches.

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