Thyroid hormones are made by the thyroid gland, situated at the base of the neck, and have far-reaching effects throughout the body.   It is estimated that 30-40% in the U.S. may suffer from undiagnosed hypothyroidism, or low thyroid, a staggering number, as the effects of being hypothyroid can be very diverse and often fairly subtle, but enough to make an individual feel constantly unwell, physically and/or emotionally.

The determination of levels of thyroid hormones arises from an elegant and complicated feedback loop between the thyroid gland, the hypothalamus, and the pituitary gland, the latter two of which are located in the brain.  The hypothalamus receives signals from the bloodstream as to levels of two important thyroid hormones, T3 and T4, and  then communicates accordingly with the pituitary via its signaling hormone called TRH (thyroid releasing hormone).  The pituitary is also monitoring levels of T3 and T4 in the bloodstream, as well as the TRH it is getting from the hypothalamus, and then produces something called TSH (thyroid stimulating hormone).  It is TSH that then travels to the thyroid to stimulate the release of T3 and T4.

After receiving the TSH from the pituitary, the thyroid then decides how much T4 and T3 to put out,  and utilizes iodide from the bloodstream for this process via the hormone TPO (thyroid peroxidase or thyroperoxidase).   The iodide then gets converted to iodine, which is then used to make T4.    The released thyroid hormone then needs to be carried to various tissues, which is accomplished via albumin, transthyretin, and thyroglobulin.  When the T4 arrives at the tissue level, it first has to convert to the more active T3, and then the T3 has to get into the cells’ nuclei in order to activate their mitochondria. This stimulation of the mitochondria, which are their “powerhouses”, releases heat and energy.   Only about 20% of the body’s T3 is actually formed in the thyroid gland, the rest is converted from T4 in such tissues as the liver and kidneys.

Obviously, in a process of this complexity lots of things have the potential to go wrong, or not function optimally.  In addition to physiological causes of dysfunction, there seems increasingly likely that our toxic and highly polluted environment and the tens of thousands of chemicals we are exposed to can wreak havoc on optimal thyroid functioning.  Some of these breakdown points are:

  • PCBs can prevent communication via TRH between the hypothalamus and pituitary
  • PCBs, DDT, and DDE can prevent TSH from docking properly at the thyroid
  • Perchlorate, bromine, chlorine, mercury and phthalates can interference with iodine’s role in the synthesis of T4
  • Many common herbicides and benzophenone (found in sunscreens) can disrupt TPO activity
  • PCBs, phthalates, PBDE, and PCP can interfere with the carrier molecules that take thyroid hormones throughout the body, preventing them from getting to your tissues
  • PCBs, mercury, triclosan (found in “antibacterial” products), and PCP can interrupt the conversion from T4 to T3 via the deiodinase enzyme.  Mercury can also cause disproportionate conversion to the inactive “reverse T3”, rather than to T3
  • PCBs, BPA and PBDE can interfere with T3 being able to get into the cell nuclei
  • PCBs, dioxins, chlordane (a pesticide) and acetochlor (an herbicide) can cause thyroid hormones to be excreted from the body too rapidly


One look at the above list should make it abundantly clear that it is of vital importance to pay close attention to the environment in our homes and workplaces, in our air, food, and water, and in the products and materials we use every day.  All of thyroid disruptors listed above are common chemicals in widespread use, and many of them lodge in the environment and in our bodies very stubbornly, degrading only very slowly, if at all.

It cannot be overstated how vital thyroid hormones are to optimal human physiology.  They are involved in many critical processes in the body, such as:

  • protecting many vital organs such as the brain, kidneys, gastrointestinal tract
  • optimizing immune system function
  • optimizing the entire cardiovascular system, by stimulating fat burning and dissolving cholesterol, thereby opening up the arteries and moderating blood pressure as they encourage elimination of waste from the cells
  • maintaining optimal circulation of blood and hormones throughout the body, helping to maintain integrity of the skin, hair, muscles, and joints
  • regulating metabolism and body temperature
  • maintaining good vision
  • regulating and maintaining healthy menstrual cycles in women


Some important symptoms of thyroid deficiency or hypothyroidism are:

  • loss of energy, experiencing constant fatigue
  • weight gain, even when dieting and exercising, slow metabolism
  • constipation
  • dry, thinning hair
  • hair loss in a generalized pattern
  • thinning nails
  • disturbances in memory and mood, including depression and dementia
  • pronounced sensitivity to cold
  • menstrual disorders in women
  • chronic hoarseness in the voice
  • peripheral neuropathy
  • sleep apnea and drowsiness during the day


It is important to note that the above list is only a very small sampling of some of the possible effects of thyroid deficiency, and that diagnosis of hypothyroidism can be very difficult, as symptoms can be very wide-ranging and often fairly subtle.  Amazingly, it is estimated that 30-40% of people in the U.S. may suffer from undiagnosed hypothyroidism, or low thyroid. It is crucial to have your free T3, free T4 and TSH tested as part of your blood work panel, as well as TPOAb  (Thyroid Peroxidase Antibodies) and TgAb (Thyroglobulin Antibodies) if Hashimoto’s Thyroiditis is a possible suspect.

Hashimoto’s is a fairly common autoimmune disorder, where the body’s immune system launches an attack on its own tissues, in this case the thyroid gland.  The immune system creates antibodies that attack thyroid cells, causing them to “leak” hormones into the blood in varying amounts, but eventually leading to the thyroid gland being “burnt out”, effectively in a permanent state of hypothyroidism.  As is the case with autoimmune disease in general, it is frequently necessary to do some detective work to discover the underlying cause(s) of Hashimoto’s, and attempt to tease out why the immune system has gone haywire and targeted the thyroid.

If you do need thyroid supplementation/treatment, Dr. Allen most likely will prescribe a natural thyroid hormone preparation such as Nature-Throid (which contains both T3 and T4), and will work with you to carefully tailor the dose for optimal results.  In addition, a good and thorough program of detoxification sometimes can help balance the thyroid, as toxic chemicals can be neutralized and made to pass out of the body, and some of the disruptions listed above can be lessened leading to more normalized thyroid functioning.

Thyroid hormone therapy often needs to be started with a small dose, with subsequent increases if necessary to find the best amount for you.  Some symptoms that you are taking too much might include some of the following, or that you have a hyperthyroid condition are:

  • Fast heartbeat
  • Feeling overheated
  • Intense sweating
  • Abnormal thirst
  • Abnormally large appetite
  • Unintended weight loss
  • Hair loss
  • Poor sleep quality
  • Nervousness
  • Trembling hands






Dr. Allen gives free lectures at the Library three to four times each year, on topics of interest from the cutting edge of integrative medicine.  If you would like to be added to our mailing list for these lectures and his other speaking engagements, please email