The normal values for the serum T4:T3 ratio are seldom discussed in the literature because measurement of serum T3 levels is not a recommended outcome in hypothyroidism (1). In a large study of approximately 3800 healthy individuals (4), the serum free T4:free T3 ratio was around 3, as opposed to a ratio of 4 in more than 1800 patients who had undergone thyroidectomy and were receiving l-thyroxine monotherapy. The corresponding serum free T4:free T3 ratio in patients continuing to receive desiccated thyroid is not well-defined, but the serum total T4:T3 ratio is known to be low (28, 50). In one study, the serum total T4:total T3 was about 40 in patients receiving desiccated thyroid and about 100 in those taking l-thyroxine monotherapy (60). Of course, this is affected by the timing of blood collection in relation to the timing of l-triiodothyronine administration, which is not commonly reported. Other key factors are the well-known poor reproducibility of the serum total T3 assay (61) and the interferences with direct measurement of free T3 (5).
The thyroid gland, situated just below the Adam’s apple on the low part of the neck, produces the thyroid hormones in the body. The thyroid gland is shaped like a butterfly and wraps itself around the trachea with two lobes attached to a central isthmus. When you eat foods containing iodine such as salt and seafood, this thyroid gland uses the idodine to produce the thyroid hormones. There are two important types of thyroid hormones produced which would be T4 or Thyrozine and T3 or Triiodothyronine (T3). These account for most of the thyroid hormones present in the bloodstream. T3 is the more active of the hormones and it affects cellular metabolism.

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In some areas of the world, iodized salt is an essential way to prevent iodine deficiency, cretinism, and mental retardation due to iodine deficiency in pregnant women. In the United States, however, many people have limited their salt intake or stopped using iodized salt, and you need enough iodine for the thyroid to function properly. An excess of iodine, however, is also linked to increased risk of thyroid disease, so staying in range and avoiding deficiency or excess is essential. 

Hashimoto’s disease is the most common autoimmune disease linked to hypothyroidism. In fact, the condition in which the autoimmune system targets the thyroid specifically is commonly known as Hashimoto’s Thyroiditis. Hashimoto’s Thyroiditis is when the immune system targets antibodies directly to the thyroid, causing inflammation of the thyroid gland and thus limiting the gland’s ability to produce its delegated hormones.


Having a thyroid condition is no picnic, but you're not alone with this health issue. According to the American Thyroid Association, more than 12 percent of the population may end up dealing with a thyroid condition at some point in their lives. And thyroid issues can be sneaky: Of the nearly 20 million Americans living with the disease, as many as 60 percent don't even realize they have it.

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