Low Thyroid Symptoms when Blood Tests are Normal
Your thyroid gland produces two main hormones – T4 and T3. T4 is not active, and has to convert to T3. T3 enters each cell and attaches to the receptor site (the specific area that receives only thyroid hormone). T3 activates the receptor sites, like turning on a light switch. Activated receptor sites stimulate the effect that thyroid hormone produces. The amount of thyroid hormone in your blood stream is measured and regulated by the pituitary gland. If there is not enough thyroid hormone, the pituitary produces a hormone called Thyroid Stimulating Hormone (TSH) which stimulates the thyroid gland to produce more thyroid hormone. If there is too much thyroid hormone, then the TSH goes down, and less hormone is produced. About 80% to 90% of your thyroid gland production is T4, and about 10 to 20% is T3. Trace amounts of T1 and T2 are also produced, but the function of these two hormones is unknown.Perhaps the best way to understand the role of thyroid hormones is to know the clinical features which occur when thyroid hormone levels are too low or too high.
Major features of low thyroid:
Low body temperature
Feeling cold when others are comfortable
Cold hands and feet
Trouble staying awake
Hair loss (especially outer third of eyebrows)
Easy weight gain
Hard time losing weight
Slowed down mental processes
Slow heart beat (pulse)
Major features of high thyroid:
Feeling hot when others are comfortable
Rapid pulse rate
Unexplained weight loss
Anxiety and feeling jittery
Speeding up of thought processes
In conventional medicine, when thyroid problems are suspected, blood tests are done to measure circulating levels of TSH and T4. If these tests are both normal, it is assumed that your thyroid gland is functioning properly, and that it is being regulated correctly by the pituitary. If TSH is high but T4 is normal, a diagnosis of “subclinical hypothyroid” is made. The assumption is that the thyroid is not doing its job adequately, and that the pituitary is working overtime to stimulate the sluggish thyroid gland. Usually this is not treated, although some people with this diagnosis do well with thyroid hormone supplementation. If T4 is too low and TSH is too high then the diagnosis of hypothyroid (low thyroid) is made. Treatment almost always involves giving oral synthetic T4 (Synthroid or Levothyroxine). The dosage is adjusted until the thyroid function tests are in the “normal range”. Usually, little or no consideration is given to the clinical picture. Often people treated with thyroid replacement hormones continue to experience features of low thyroid in spite of perfect control according to the blood tests.
There may be several reasons why thyroid function could be low in spite of normal blood levels.
1. Poor response to synthetic T4 hormone. An alternative is to try “natural thyroid hormone” (Armour thyroid, Westhroid, Nature -throid). These hormones are derived from pork thyroid gland tissue. Since pigs produce thyroid hormones much like humans do, these hormones are much closer to human thyroid hormone than synthetics. Natural thyroid has 80% T4, but also contains 20% T3 along with trace amounts of T1 and T2. Many people have a substantially better response to natural thyroid than they do to straight synthetic T4. The reason for this improved response is unknown, but could be due to the active T3, or some effect of the T1 or T2. For those taking synthetic T4 with poor response, a clinical trial of natural thyroid would make sense.
2. Thyroid hormone is usually given only once a day. This is usually okay for synthetic T4, since the half life of T4 is over one week. In other words, if you take a dose of T4 today, in one week, half of it will still be in your system. The half life of T3 is only 6 – 8 hours. Dividing the dose into 2 or 3 doses daily may produce more smooth, even results.
3. Pathogenic microbes like Candida (yeast) or bacteria seem to interfere with thyroid function. Whether it is the microbe itself, the toxic compounds that they produce, or the response from your immune system that interferes is unknown. Many people who have an infection or imbalance with microbes have the same clinical features as those with hypothroidism. Correcting the imbalance or infection often clears up the low thyroid features.
4. Deficiency of iodine may interfere with thyroid function. Iodine is needed for the formation of thyroid hormone. It is also needed by the receptor sites upon which the thyroid hormone acts. Without iodine, the receptor sites are not activated optimally, and low thyroid symptoms remain in spite of treatment with thyroid hormone. Measuring the amount of iodine in your system is difficult and the optimal amount that should be in your stores is unknown. If low thyroid symptoms persist in spite of normal blood levels of thyroid, then a clinical trial of iodine makes sense. The amount of iodine to take is very controversial. Some experts believe that almost any amount is safe, and that the thyroid that your body doesn’t use is just excreted through the kidneys. Others believe that a diseased or malfunctioning thyroid gland is not capable of excreting the excess, that it concentrates in the thyroid gland and can cause damage. It seems prudent to try only 1 drop of Lugol’s iodine, or iodine in less concentrated forms.
5. Often there is a problem with converting T4 to T3. We have built-in starvation defenses that allow us to survive starvation by conserving energy when inadequate food is available. One of these starvation mechanisms is a change in your response to thyroid hormone. In normal circumstances 90% of the T4 produced converts to active T3, and 10% converts to reverse T3 (RT3). Because RT3 is a T3 hormone, it can attach to the receptor sites designed for T3. Unlike regular T3, RT3 does not activate the receptor sites. RT3 binds to the receptor sites and blocks them, making them unavailable to be activated by active T3. If for any reason a person takes in less food than required to meet energy needs, or if other stress exists (like having a baby, having surgery, or emotional stress) then starvation defenses kick in, less T4 is converted to active T3, and more converted to RT3. When you have too much RT3 and not enough active T3, you will develop clinical features of low thyroid. Your body temperature will fall, you will feel cold, your energy levels will fall and you will just want to lie around conserving energy. This great starvation defense may have served our ancestors very well and kept them alive in times of food shortage. Today, when plenty of food is available, this defense is maladaptive and does not serve you as well.
The amount of T3 and RT3 in your bloodstream can be measured by lab tests. The ratio between these two hormones is what really counts. To establish the ratio, the amount of T3 is divided by the amount of RT3 (T3/RT3). Since ten times as much active T3 should be present as T4, the ratio should yield a number of ten or more. The lower the number, the worse the ratio between T3 and RT3.