Thyroid hormones regulate the metabolism of protein, fat, carbohydrates, involved in the producation of growth hormones, vitamin utilisation, increase of absorption of glucose from gut and uptake into muscles and fat and helps break down stored sugar in the liver. This process helps with temperature regulation, which is why under-active thyroid patients have a low core temperature and experience fatigue.
There are many symptoms of low thyroid activity but the classic symptoms are cold extremities, cold intolerance and feel chilly. Others like weight gain and early morning fatigue are very common. Depression, dry and or brittle hair, dry skin, eczema, acne, puffy eye lids/face, brittle nails, difficult menses, constipation, mentally sluggish, headaches, insomnia, late morning fatigue, evening fatigue, muscle cramping and low sex drive.
The thyroid gland is located in the neck and responds to thyroid stimulating hormone (TSH) from the hypothalamus which manufactures thyroid hormone thyrosine (T4). In the blood the T4 gets converted to an active form called T3 and a non active competitor (which is a nuisance) called reverse T3 (rT3). T3 binds to and activates receptors and penetrates the cells that govern metabolism, but if rT3 binds to these same receptors it does not activate metabolism but in turn decrease metabolism thus the transport of thyroid hormones into our cells is the most important factor in assessing thyroid activity.
T3 is considered the major regulator in mitochondrial activity. Mitochondria are part of our cells that are responsible to produce energy for that particular cell. The most important determinant of thyroid activity is the internal cellular level of T3 and the most important determinant of interal T3 level is the activity of the cellular thyroid transporters. A reducation in thyroid transport is seen in a wide variety of conditions, such as insulin resistance, diabetes, depression, bipolar disorders, anxiety, chronic dieting, ageing, chronic fatigue syndrome, fibromyalgia, MS, parkinsons, alzheimers, migraines and stress. It is important to work with your physician to find the major cause of an underactive thyroid, whether it is inadequate production of T4, an inbalance of TSH release, hypothalaemic disorder or the conversion failure of T4 to T3. Iodine deficiency is a common cause so it low tyrosine (more common in vegetarians, vegans and body builders). Other co-factors that may be due to poor nutrition include riboflavin (B2), niacine, magnesium, selenium, zinc and copper. Selenium is one of the main minerals in assisting the conversion of T4 to active T3. Selenium levels need to be checked, in particular the red blood cell levels as it is more reflective of blood tissue levels. If the body is low in selenium, more T4 coverts to rT3, the inactive form. We can suggest a dose then re-test levels in 3 months. Major stress is also another reason that favours more rT3 production from T4 instead of active T3 production. A saliva cortisol level test can help define whether stress is a determining factor in affecting the production of active T3.
Normally the body converts T4 to T3 and rT3 in a 50:50 ratio. If there is a decreased conversion to active T3, it is always accompanied in an increase of rT3 conversion. This is why if T4 is given alone (common commercial products include oroxine and eutroxsig) the imbalance conversion will make the situation worse. This explains why when blood comes back and all the thyroid levels are optimal, yet the patient is still symptomatic and suffering signs of hypo-metabolism.
When testing thyroid levels indicators required include TSH, total T4 ( includes both bound & free), free T4, total T3, free T3 and rT3 are available. Reverse T3 is an excellent marker for reduced cellular T4 and T3 levels not detected by TSH or serum T4 and T3 levels.
TSH does not measure the thyroid efficacy, but it tests the brain’s happiness with the amount of thyroid hormone in the system.
In treating patients , they should be patient specific.
Treatment options include Levo-thyroxine (T4), T3 slow release or combination T4/T3 porcine thyroid extract ( in a ratio of 1:4.2 T3 to T4 ) or bioidentical T3 and T4 combinations which are physiologically mimic human hormones ( in a ratio of 1:3.3 T3 to T4) which is closer to human physiological levels. These can all be custom made in our laboratory with the advise of your physician.
Sometimes treating with a slow release T3 alone is better as it does not convert to reverse T3. Our thyroid porcine in a 60mg dose contains 9mcg of T3 to 38mcg of T4. Dosage guidelines would be to titrate, start therapy then re-test after 5-6 weeks and adjust according to labs and symptoms. Always starting conservatively and working upwards.