Low Thyroid? What you need to know


Positioned on the front of your windpipe at the front of the neck, just below your Adams apple, the thyroid is a butterfly-shaped gland. The thyroid has two side lobes, connected by a bridge (isthmus) in the middle. the thyroid is rich with blood vessels and nerves important for voice quality. Thyroid hormones act throughout the body, influencing metabolism, growth and development, and body temperature. During infancy and childhood, adequate thyroid hormone is crucial for brain development.

What does it do?

Thyroid is the regulator of your overall metabolism. It sets your basal body temperature via the hypothalamus and pituitary gland at the base of the brain, thyroid regulates many metabolic processes including protein synthesis and fat metabolism.

Specifically the thyroid gland secretes two types of thyroid hormones T4 and T3. Although most of the thyroid hormone in circulation is T4, it’s T3 that’s most important. At the cellular level, T3 is the one that binds to receptors – most of this “bioactive” hormone comes from the deconstruction of T4 to T3. The most common thyroid condition that fitness professionals encounter with clients is hypothyroid condition - a chronically suppressed production of active thyroid.

Don't let decreased active thyroid get in the way of your progress - Sam O'Reily


While it can have hereditary aspects, a history of chronic dieting and calorie restriction with an excessive approach to exercise will result in a decrease in active thyroid.

Most often overweight females that are diagnosed with a thyroid condition is the result of years of yo-yo dieting and inadequate nutrition. A decrease in active thyroid is also the main cause of ‘metabolic slow down’, a plateau in fat loss and disruption of fat metabolism in general.

The second cause of decreased active thyroid is cortisol. When the cortisol receptors on the pituitary gland are activated, they reduce the production of thyroid stimulating hormone TSH, which is the messenger between the hypothalamus (brain) and thyroid gland. High circulating cortisol levels occur from lack of sleep, too much stress and medications – anti-depressants and anti-inflams.

Cortisol affects the T4- to T3 conversion process. A specific enzyme called 5’-deiodinase is impaired in the presence of cortisol. When you consider the potential causes as described above, you can see how many people may fall into this category.

What you need to be aware of...

The only way to obtain an accurate diagnosis of a decreased production in active thyroid is via the correct pathology which I will explain in a moment. Natropathy, homeopathy, crystals etc, cannot not provide an accurate diagnosis of the condition.  Additionally, when traditional blood work is obtained, often T4 levels appear to be in normal range, while T3 is ‘low’ but still within normal range. Just because these levels still fall within ‘normal’ range, does not mean ‘optimal’. While many overweight people have thyroid levels that are ‘normal’ they are not ideal for fat metabolism. To shed fat requires optimal health. We don’t just want good health, we need optimal health.

No matter where you start from, you can make great improvements - Tina Sims

Indicators of metabolic rate are surprisingly easy to observe – body temp measure via a theromoscan inner ear infrared thermometer, is a simple, cost effective way to measure body temp and therefore metabolism. Every morning before you get out of bed, stick the device in your ear and get a reading – For optimum health (and fat loss) we need a reading of 36.55 to 36.77 degrees C.

If readings are on the low side of this range, you may want to follow my principles bellow. If you suspect you have a decreased production in active thyroid, this can only really be determined clearly via blood work that encorporates 3 specific thyroid tests.

Thyroid Stimulating Hormone (TSH) assay.

This recent advancement in thyroid tests is called a “sensitive thyrotropin assay” because older TSH tests were not sensitive enough.

Normal .3 - 5 µU/ml
Subclinical 5.1 – 20 µU/ml
High 20 µU/ml

TSH is produced in the pituitary. Most hypothyroidism which is a deficiency of both T3 and T4 is usually indicated by an over production of TSH. The older TSH tests only when down to 1 µU/ml. This is a good test to complete because overmedication (with thyroid hormone), T3 & T4 levels can look normal because of the medication. During any medication, if TSH too low, you will know that too much medication is being used.

When people “diet” (restrict calories) a reading of 20 µU/ml will usually predict low T4 & T3. With a normal person, a thyroid specialist will try to balance the hormones so that T4 levels are as normal as possible and TSH is still above .3 µU/ml. Unfortunately, the dosage sometimes required to achieve the desired body temperatures described earlier will often be so high it can suppress TSH, and even after stopping medication it can take TSH levels to get back to normal.

As I said previously, in people that "diet" a reading of 20 µU/ml will usually predict low T4 & T3. Therefore T3 and T4 assessment is necessary.

Free T4 test

Technically this test is called an equilibrium dialysis – its the only T4 test you want to do. There are others, (such as Total T4 and Free T4 Index) but they are not accurate enough.

The Free T4 test is the most expensive and some labs don’t do it but as I said it’d by far the most accurate.

Normal Free T4 ranges from 4.5 to 12.5 µg/dl. Athletic people are rarely below this range. If body temperature is low and T4 is low, a medication like Synthroid probably won’t help because raising T4 won’t raise T3 much at all. Remember, unlike classic hypothyroidism in sedentary people, a dieting induced below par thyroid function is caused by faulty conversion of T4 to T3.

Radioimmunoassay Free T3 test

This is the most important one for active people and metabolically speaking – this is where the action is. Unfortunately, thyroid specialists work mostly with T4 as its hard to get consistent readings with T3 (as opposed to T4) as it is unbound (T4 is 99.9% bound). After T3 medication, blood levels will peak within 4 hours and decline rapidly, and most specialists don’t like to work within these variables.

Having said that, as long as you have the blood draw first thing in the morning and you don’t take T3 medication before the test, a reliable T3 reading shouldn’t be a problem.

The Free T3 blood test readings should be somewhere between 80 – 175 ng/dl. Pay close attention to this, dieting-induced or cortisol medication-induced reduction is usually a problem with T4 converting to T3. A low body temp reading will confirm this.

To clarify, a “dieting-induced” or “cortisol medication-induced” reduction in T3 is supported by a TSH and T4 reading that are somewhere within normal ranges but T3 is low! That is, below 80ng/dl or at least the low end of the normal values.

Here is the irony...

The irony is, even if you are diagnosed with a decreased production in active thyroid, medication only does so much. To improve health, body composition (your shape) and performance really does take a proactive approach to the principles I've outlined below. Living with a decreased production in active thyroid simply means applying these principles with even more conviction to address the main contributors. This will improve the effectiveness of the pharmacology and ultimately, in many cases reduce the amount of medication required..

In just 12 weeks you can can make some big improvements - Kelly Thomas

1. Resistance training designed to build muscle
Essential to normalize/restore anabolic hormone production that are essential to fat metabolism and synthesis of lean muscle
Increase resting metabolic rate by building muscle mass.
Intense contractile activity ↑ GLUT expression -mechanism of increased insulin sensitivity.

2. ICE (Intense Cardio Exercise) training
Promotes ↑ GLUT expression
Reduces cortical responses
Increases bioactive GH in circulation

3. Nutrient Timing
Works in sync with ↑GLUT expression to optimize body composition.
Nutrient timing is a key non-pharmalogical means of promoting the nutrition partitioning effect - dietary nutrition is channeled to lean tissue and away from fat storage to improve body composition.

4. Increased meal frequency
Reduces blood insulin responses and peaks (key for reversing hyperinsulinemia, see my article on Diabetes)

5. Meals high in protein
Promotes lower blood insulin responses. Promotes thermogenesis and body temperature.

6. Correct plant food selections
Unprocessed plant food provide the material that optimize thyroid function. Often people diagnosed with a thyroid condition don't like vegetables.
Strategic increases in unprocessed plant food is the only way to reverse thyroid conditions caused by the Metabolic Slow down and calorie restriction
↑ muscle glycogen (key for work capacity).
Photochemicals in plant foods help to restore insulin and thyroid receptor function

7. Omega-3 fats Reduce inflammation at the cellular level
Key mechanism of reversing insulin resistance.

8. Reducing sugar and beverages helps reduce blood insulin surges and lows.
(key for reversing hyperinsulinemia).

This is article is from Guide to Working With Special Populations - part of the MP Level 1 Coaching Systems