Thyroid hormone is probably the single strongest stimulator of the metabolism, and therefore sluggish thyroid function is almost always associated with stubborn weight problems.
Although decreased thyroid function can be due to problems with the gland itself, in many cases other factors are actually to blame.
Let's examine the whole thyroid hormone system so that you can better understand where things can go wrong and how its function can often be improved with lifestyle changes.
The stimulation of metabolism actually begins in a part of the brain called the hypothalamus - the master hormone controller.
The hypothalmus senses the need for more or less thyroid hormone production and when more is needed, it signals the pituitary gland to produce a hormone called TSH (you may have seen this hormone listed on a blood test for thyroid function).
TSH stimulates the Thyroid gland to produce the inactive form of thyroid hormone, called T4.
When the inactive T4 hormone levels increase, it is taken up by the liver and converted to the active form of the hormone, known as T3.
The T3 hormone then acts on receptor sites on the cells of the body and causes the cells to produce more mitochondria, which can be thought of a microscopic power plants inside the cells.
Mitochondria burn stored fat and sugar to produce energy for various cellular functions (and on a larger scale, for the whole body).
When something goes wrong in the thyroid system, the body does not burn fat and sugar as much, so there is a tendency for weight gain.
As the cells of the body are not procuding as much energy, a common symptom that develops is chronic fatigue.
And because there is not sufficient energy for certain cellular functions, healing and tissue regeneration may be depressed - this is most commonly noticed as hair loss and brittle nails.
There are several possible reasons why the system might not work as well as it should.
First, there may not be sufficient stimulation of the body to cause the hypothalamus to start the process.
The primary stimulator of the thyroid system is exercise - primarily short bursts of intense exercise.
In other words, for healthy metabolic function, it is more effective to do interval training in which you do repetetive bursts of intense activity with rest in between, than it is to do long periods of low-intensity exercise, but any form of exercise is helpful.
An additional potential problem is damage to the gland itself, which is most commonly due to infection or sometimes by radiation exposure.
Radiation exposure could come from accidental or long-term occupational contact, or in some individuals, may have been intentional as a part of cancer treatment.
In the case of actual thyroid damage, some type of thyroid medication will usually be necessary to compensate.
Yet another possible problem in the thyroid system is poor conversion of the inactive T4 hormone to the active T3 hormone by the liver.
This typically occurs with poor lifestyle - excessive alcohol and/or drug use, and/or bad diet (especially a diet high in fats and animal proteins).
In many cases, liver function can be improved with healthy lifestyle changes, and this will lead to improved T4 hormone activation.
Active thyroid hormone may be interfered with at the cellular receptor sites and may not be able to properly signal the cells to produce more mitochondria.
This is a common side-effect of estrogen and estrogen-like chemicals.
The most common sources of estrogen interference with T3 hormone function are birth control medications and estrogen replacement therapy.
If you have experienced weight gain and other thyroid-related symptoms since starting on birth control or hormone replacement, you may wish to consult with your physician about other options.
Finally, the formation of mitochondria can be interfered with by the presence of certain chemicals.
Sodium benzoate, a preservative found in many processed foods and beverages (especially soft-drinks) can damage the genetic material within the cells needed for mitochondrial formation.
Here again, cleaning up the diet can be very beneficial to overall thyroid hormone function and the ultimate goal of weight control.
To sum things up, there are steps you can take to maximize the metabolism-stimulating effects of the thyroid.
First, regular exercise is important, and interval-training is the most effective.
Next, avoid excessive alcohol consumption, avoid drugs and medications except for those that are absolutely necessary, and keep fat and protein intake to a moderate level so as not to overwork the liver.
In addition, you may wish to consult with your doctor if you are using any kind of birth control or hormone replacement medication containing estrogen.
Finally, avoid the preservative sodium benzoate in order to avoid interfering with the production of your cellular "power plants", the mitochondria.
In most cases these steps will gradually normalize thyroid hormone function and you will find that weight control becomes much easier.
In a few cases, medical treatment for thyroid damage may be needed, but simple lifestyle changes are often the most effective means of improving metabolism.