As a butterfly shaped gland located in the anterior portion of the neck, the purpose of the thyroid is to produce thyroid hormone, which works in almost every cell in the body. Due to the widespread action of thyroid hormone, the thyroid is often referred to as the master of metabolism.
Approximately 1 in 10 Canadians suffers from some degree of thyroid dysfunction, the most common diagnosis being hypothyroidism, or an under active thyroid. Hypothyroidism is much more common in woman than men.
Individuals suffering from decreased thyroid function often present with some or all of the following:
• weight gain
• cold intolerance
• decreased libido
• dry skin
• brittle hair and nails
• muscle cramps
• menstrual irregularities
• depression or low mood
• decreased cognitive functioning
Low thyroid function is often a result of prolonged stress, nutrient deficiencies, or an autoimmune condition known as Hashimoto’s thyroiditis, a process by which the patient’s immune system produces antibodies that attack thyroperoxidase (TPO), the enzyme responsible for the production of thyroid hormones from dietary iodine and tyrosine.
Under normal conditions in the thyroid gland, TPO catalyzes the production of two thyroid hormones, triiodothyronin (T3) and thyroxine (T4), typically, in a ratio of 2:8 respectively. An additional 30% of circulating T4 is converted to T3 in the liver and other organs, which is important, since T3 is 4 to 10 times more powerful than T4. This process is termed peripheral conversion, and depends on dietary selenium and zinc. If either of these nutrients are deficient, peripheral conversion is less effective, and reverse T3 (rT3) is produced, reducing circulating or Free T3 in the blood. Since T3 is much more powerful that T4, decreased Free T3 can contribute to symptoms of hypothyroidism even when levels of T4 are normal. Research suggests that the ideal ratio of T3:T4 is approximately 15:1.
Diagnosing Thyroid Dysfunction
If you are suffering from some or all of the symptoms listed above, see your doctor. The first line blood test used to identity thyroid dysfunction is measuring thyroid stimulating hormone, or TSH. TSH is equivalent to a chemical messenger released by the anterior pituitary. The anterior pituitary releases TSH in response to low levels of T4, encouraging the thyroid to increase production of this hormone. When the thyroid is unable to keep up with the body’s need for thyroid hormone, TSH secretion continues, and blood concentration increases.
In BC, the normal reference range for TSH is currently 0.3 – 5.6 mU/L. Unfortunately, doctors using this reference range often miss individuals with mild to moderate thyroid dysfunction leaving them untreated and without a diagnosis. According to the Whickham survey, the largest population based thyroid study ever conducted, serum TSH > 2.5 mU/L was indicative of mild to moderate thyroid dysfunction, while levels higher than this often confirmed overt hypothyroidism.
In response to this study, the American association of Endocrinologists changed their guidelines with respect to TSH references ranges in 2003, indicating that physicians should consider additional testing and treatment for any patients with a TSH level over 3.0 mU/L.
Unfortunately, if issues with peripheral conversion are contributing to symptoms of hypothyroidism, TSH may test within normal limits. This is why it is so important to check free T3 and free T4 in addition to TSH. Anti-TPO (a measurement of autoimmune dysfunction affecting the thyroid) should also be tested in order to obtain the most complete diagnosis.
Levo-thyroxine (synthroid) or synthetic T4 is the treatment of choice for hypothyroidism. Some patients feel much better after starting thyroid hormone replacement therapy, although some do not. In my experience as a naturopathic doctor, supplementing a combination of T3 and T4 in a ratio specific to the patient, can mimic thyroid function more closely than synthroid alone.
Most patients with an under active thyroid also need help and guidance in managing stress, and many need nutritional supplementation to support normal thyroid function and peripheral conversion.
If you feel you might benefit from thyroid testing, or would like guidance with respect to diagnosing your symptoms, book an appointment!
Yours in good health,
Dr. Kaleigh Anstett