OPTIMIZE YOUR HEALTH
Thyroid Awareness

Is Your Thyroid Sluggish?
By Jannet Huang, MD, FRCPC, FACE

Up to 27 million Americans are affected by thyroid disorders, although more than half remain undiagnosed. Hashimoto’s thyroiditis is the most common cause of hypothyroidism, an under-active thyroid, which is the most prevalent thyroid disease in US. Symptoms of hypothyroidism include fatigue, weight gain, feeling cold, muscle aches, constipation, hair loss, dry skin and difficulty with concentration and memory. Women with thyroid disease can experience menstrual abnormalities.

We approach individuals with possible thyroid dysfunction by carefully listening to their concerns and conducting a comprehensive history, physical examination and laboratory testing. The best screening test for thyroid dysfunction is TSH (thyroid stimulating hormone), which is the signal the pituitary (“master gland”) makes to tell the thyroid to produce thyroid hormones (T4 and T3). When a person’s thyroid is underactive, the pituitary gland senses the decline in thyroid levels and tries to compensate by sending out more stimulating signal. TSH is therefore elevated when a person is hypothyroid.

The “normal range” that is reported by laboratories is very wide (usually 0.35-5.50), but studies have shown that people with normal thyroid function have a TSH close to 1.0 and each individual has a set point around which their TSH stays. The AACE (American Association of Clinical Endocrinologist) states that normal TSH should be in the range of 0.3-3.0. At the Center we also recommend testing Free T4 and Free T3 levels which are the thyroid hormone levels that are available to the tissues for utilization, as opposed to the total T4 and T3 levels that are in circulation. We also test for antibodies against the thyroid (anti-TPO and anti-thyroglobulin antibodies) which provides confirmation for Hashimoto’s thyroiditis.

Most physicians use synthetic levothyroxine (T4) preparations (identical to the human T4) for the initial treatment of all forms of hypothyroidism. T4 is most frequently used because tissues convert T4 to the bioactive T3. T4 is more stable than T3 and has a longer half-life, therefore providing more even blood levels. Many patients do well on synthetic T4 (eg. Synthroid, Levoxyl, Unithroid). It is important that you do not switch from one brand to another or from brand to generic without specific instruction from your physician since different brands and generic T4 preparations are not bioequivalent. For patients whose symptoms are not resolved by T4 alone, I recommend adding T3 (eg. cytomel or compounded slow release T3). Even though several studies have not been able to shown obvious measurable advantage of T4+T3 combination over T4 alone, some individuals prefer the T4+T3 combination, finding their energy, cognition and weight better on the combination therapy. Others may find that they do best on the “natural thyroid” which is desiccated porcine thyroid preparation (eg. Armour Thyroid) which contains T4, T3 and probably other hormones/proteins the thyroid produces. Proponents of Armour thyroid feel that it is a complete preparation while opponents argue that porcine thyroid and human thyroid have different T4/T3 ratios. Our approach is to attempt to find the right preparation that suits each individual the best to optimize their quality of life. We aim at a target TSH of between 0.3-2.0, along with listening carefully to each individual’s symptoms to recommend any dose or preparation adjustment.

—January 2007

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