the American Thyroid Association®. 1 Blood tests to measure TsH, T4, T3 and free T4 are birth control pills, high levels of total T4 and T3 can exist. The relationship between T4 and TSH levels. Image source: Specifically, Total T4 and T3 and/or Free T4 and T3 can be tested. Total T4 and. A free or total triiodothyronine (free T3 or total T3) test is used to assess thyroid gland function, to Acute illness may affect thyroid testing test results. .. American Association of Clinical Endocrinologists: About Your Thyroid.
Avoid falling into this trap! The free T3 can give you seriously helpful information about how your thyroid is functioning. But what is a "normal" or "healthy" range? What levels should you look for when you test for this simple lab test? This is a simple yet very important question. The answer is that it varies based on which lab company is drawing and running your bloodwork.
And that happens for this reason: Each lab company creates their own "reference ranges" that your result is compared to. That means the reference range is compiled of a bunch of both healthy and unhealthy people which can skew the range.Reverse T3 Treatment Guide + How to “Flush” it out of Your Body
You don't want to be compared to someone who is in their 80's with multiple health conditions. So how do you do this? This isn't a perfect way to do it, but it is much better than potentially comparing yourself to unhealthy people.
Let's use this as an example: This example shows a free T3 of 2. If we break down the difference between 3. So you want your result to ideally fall between 2. You can apply this same methodology to your lab test.
Is having a High Free T3 Dangerous? What you will find, however, is that your free T3 will vary based on when you take your thyroid medication8 the type of thyroid medication you are taking and when you check your blood work. To prevent abnormalities in your blood work you will want to follow these basic rules: Make sure to test your blood work about 24 hours after you take your thyroid medication.
How reliable are free thyroid and total T3 hormone assays?
This will help prevent abnormal highs when testing. You want to look at the lowest level of thyroid hormone that is in your body prior to your next dose. Checking at hour 24 assuming you take your thyroid medication every 24 hours will show you the lowest that your free T3 will be right before you take your medication.
Don't check your blood work right after you take your thyroid medication. This will give you a value which is falsely elevated and not indicative of what your levels will be throughout the day.
Hypothyroidism is more commonly found with increasing age and female gender, with a female to male ratio of approximately 9: The signs and symptoms of hypothyroidism are dependent on the degree of thyroid hormone deficiency, the acuity of disease development, and the duration of disease. The consequences of untreated or wrongly treated hypothyroidism can be significant, ranging from nonspecific symptoms to life-threatening manifestations. Thus, accurate and timely diagnosis of hypothyroidism is essential.
Extra-thyroidal diseases are also important conditions requiring accurate measurement of thyroid hormones.
Why Free T3 & Total T3 are the Most Important Thyroid Lab Tests
For example, euthyroid sick syndrome occurs in critically ill patients and is characterized by low FT3, normal to low TSH, frequently elevated reverse T3, and low FT4 if of prolonged duration; an accurate FT3 is especially important to the diagnosis 7. Other important conditions for measurement of free thyroid hormones include those associated with drugs that affect thyroid function, peripheral metabolism of thyroid hormones such as amiodarone 8or binding of thyroid hormones to plasma proteins.
The majority of circulating thyroid hormones are bound to serum proteins, allowing for their transport and extension of half-life; however, carrier protein binding makes thyroid hormones unavailable to tissues and thus protein bound T3 and T4 are considered inactive.
The remainder of circulating T3 and T4 are bound to the low-affinity proteins albumin and transthyretin. Changes in binding protein concentrations occur in a number of conditions, and can significantly impact the total thyroid hormone concentrations. According to the free hormone hypothesis, only the free thyroid hormone is available for cellular uptake, while the bound form is not immediately available Recently it has been shown that T4 has a very poor affinity for the thyroid hormone nuclear receptor while T3 is avidly bound to the latter and responsible for the clinical effects, indicating that T4 is the prehormone and needs to be converted to the active hormone T3 13 The measurement of FT3 and FT4 are the most clinically relevant for the evaluation of thyroid disorders, with total thyroid hormones being affected by variations in binding protein concentrations.
It is essential that free thyroid hormone measurement accurately assess hormone concentration even in the presence of significant variation in the concentration of binding proteins that occur in a variety of physiological and disease states.
This is clearly achievable using equilibrium dialysis or ultrafiltration to effect the separation and then measure the free thyroid concentrations in the dialysate or ultrafiltrate. Increasing evidence by our group and others indicates inaccurate values are being generated for thyroid hormones by the commonly used immunoassay platforms.
Shortly after arriving he met with Dr Wellington Hung, the head of endocrinology and a thyroid expert. To establish why this happened, we sent these samples to Nichols laboratory for measurement of FT4 by equilibrium dialysis followed by immunoassay. Work by our team over the past 2 decades has verified that immunoassays for FT4, FT3, and TT3 frequently overestimate values for all 3 tests especially at low concentrations 314 — This review discusses the assays available for total and free thyroid hormone measurement.
Specific limitations of commonly used assays are discussed, and issues relevant to treatment are highlighted. Limitations of current free thyroid hormone immunoassays The majority of laboratories use one-step direct analog immunoassay for determination of free thyroid hormone.
A complete review of assay methodology for total and free thyroid hormone measurement has been published elsewhere A number of disease and physiological states have been shown to impact free thyroid hormone measurement. Furthermore, free thyroid measurements show poor agreement between various assays.