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If you are struggling with chronic health issues – the way I used to – you probably have piles of lab tests that can potentially tell you a lot about your health. T4 or T3 may be one of them. However, doctors never had enough time to explain it properly. They will only notice it if the lab flags your test results as outside of normal. But what if all your results are coming back normal, yet you know you are feeling nowhere near healthy? They may even tell you there is nothing wrong with you, and that it’s all in your head – I’ve been there.

Lab Test Analyzer is the tool I wish I had when I was dealing with all my health issues. Instead of normal, it will tell you the optimal values for T4 and T3 and many other lab tests. And if you are outside the optimal range, it will give you actionable tips and recommendations that will help you get there.


Introduction to T3 and T4

The thyroid gland is located in the base of the neck in a typical body and is involved in secreting important hormones T4 (thyroxine) and T3 (triiodothyronine).

T3 contains 3 iodine atoms and is created from the breakdown of T4. The breakdown of T4 is encouraged by the thyroid stimulating hormone.

T4 is synthesized from residues of the amino acid tyrosine, found in thyroglobulin (a protein created in the thyroid). It contains 4 iodine atoms.

T4 allows the body to control the more active T3 better.

If there are too much of the thyroid hormones in the bloodstream, the hypothalamus will signal the pituitary gland (via TRH) to produce TSH for the thyroid to release more T3 and T4.

Once there is enough of these hormones, the hypothalamus will be signaled to stop the release of TRH and the cascade of actions to increase T3 and T4.

How Thyroid Hormones Works

Thyroid Hormones Increase Metabolism

T3 binds to thyroid hormone receptors outside of the cells and gets internalized into the nucleus, which then subsequently changes gene expression (cellular production of certain proteins and hormones).

These genes include PPAR-gamma, NRF1, NRF2, and other transcription factors that work with these genes (R).

Thyroid hormone can partner with another receptor to change gene expression. The partner could be another thyroid hormone receptor, RXR (vitamin A receptor), or VDR (vitamin D receptor) (R).

Thyroid Hormone Stimulates the Mitochondria

T3 stimulates increases oxygen consumption and heat production by the mitochondria (R).

T3 stimulates the production of new mitochondria (R, R2).

Therefore, mitochondrial dysfunction can results in symptoms of hypothyroidism, even in the presence of healthy levels of thyroid hormones.

Thyroid Panels

You can request from your doctor to test your T4 and T3. Conventional doctors will look at high or low thyroid hormone levels and not mention anything. Sometimes, a lab result may be in the reference range, but not actually be in the optimal range. Reference ranges are taken by essentially averaging a mostly sick or unhealthy population of people because people who go to the doctor to get blood tests are more likely to be sick. This is why thyroid hormones even in the ‘normal’ range can be unhealthy and indicate that certain processes in the body aren’t optimal. Lab Test Analyzer will let you know if your TSH, T4 and T3 are optimal and what you can do to get them there if they aren’t.

MeasurementFull NameUnitReference RangeExplanationReference
fT3Free T3pg/ml2.5 - 4.3
fT4Free T4ng/dL0.9 - 1.7
rT3Reverse T3pg/mL90.0-350.0
T3Triiodothyronine (free and bound)ng/dL75 - 200
T4Tetraiodothyronine or Thyroxine (free T4)ug/dL6 - 12
TBGThyroxine Binding Globulinmg/dL1.1 - 2.1
TGAbThyroglobulin AntibodyIU/ml<4
TPOThyroid Peroxidase AntibodyIU/ml<35
TRHThyrotropin Releasing HormoneU/mL5 - 25
TSHThyroid Stimulating HormoneU/mL0.27 - 4.2
T3 uptake%

What Do Thyroid Hormones Control

T3 and T4 aid cells into creating energy.

It affects:

  • Breathing
  • Metabolism (creating energy from calories)
  • Heart rate
  • The nervous system
  • Body weight
  • Muscle strength
  • Menstrual cycles
  • Body temperature
  • Cholesterol levels
  • Growth and development
  • Intestinal flow
  • Digestion

Hyperthyroid Symptoms

Higher levels of thyroid hormones will cause a faster heart rate, diarrhea and potentially weight loss .

Hyperthyroid (too much T3 or T4) symptoms include:

  • Anxiety
  • Irritability or moodiness
  • Nervousness
  • Hyperactivity
  • Sweating or sensitivity to high temperatures
  • Hand trembling
  • Hair loss
  • Missed or light menstrual periods

Hypothyroid Symptoms

Low levels of T3 will cause slower heart rate, constipation and potentially weight gain.

Hypothyroidism (too little T3 or T4) symptoms include:

  • Trouble sleeping
  • Tiredness and fatigue
  • Difficulty concentrating
  • Dry skin and hair
  • Depression
  • Sensitivity to cold temperature
  • Frequent, heavy periods
  • Joint and muscle pain

Adequate Iodine Intake

Everyone should have an adequate dose of iodine everyday.

Age Male Female Pregnancy Lactation
Birth to 6 months 110 mcg* 110 mcg*
7–12 months 130 mcg* 130 mcg*
1–3 years 90 mcg 90 mcg
4–8 years 90 mcg 90 mcg
9–13 years 120 mcg 120 mcg
14–18 years 150 mcg 150 mcg 220 mcg 290 mcg
19+ years 150 mcg 150 mcg 220 mcg 290 mcg
  • Adequate Intake (AI)

*mcg stands for micrograms.


A  benign goiter is the swelling of the thyroid gland when adequate iodine is not received from the body’s diet.

The Hypothalamus-Pituitary-Thyroid (HPT) Axis


The hypothalamus, pituitary, and the thyroid gland (also called the hypothalamic/pituitary/thyroid or HPT axis) control thyroid hormone levels (R).

Thyrotropin-releasing hormone (TRH) made in the hypothalamus binds to the receptors in the pituitary, causing it to release the thyroid stimulating hormone (TSH), which then stimulates T4 production (R).

If there is too little of the thyroid hormones in the bloodstream, the hypothalamus signals the pituitary gland (via TRH) to produce TSH for the thyroid to release more T3 and T4.

Once there is enough of these hormones, the hypothalamus is signaled to stop the release of TRH and the cascade of actions to increase T3 and T4.

High free T4 and free T3 levels signal the pituitary to adjust TSH and TRH levels (R).

Low free T3 and free T4 increase TSH, so TSH is typically the only hormone measured in a blood test to screen for hypothyroidism.

Somatostatin and dopamine from the hypothalamus also reduce TSH levels, thus reducing thyroid hormones (R).

Iodine is required for the synthesis of thyroid hormones.

rT3 is the mirror image of T3. It binds to the thyroid receptor but does not activate the receptor. It competes with T3 and prevents T3 from binding to and activating the thyroid receptor.

Conversion of T4 to the more active T3

Both T3 and T4 are produced in the thyroid gland, although T3 is much more potent than T4.

In the blood, T4 levels are around 45 fold higher (90 nM) than T3 (2 nM) (R).

Most T3 is produced by removing an iodine from T4 in a process that requires selenium (R).

The total activity of T3 thyroid hormone in the body depends on the enzyme that converts T4 to T3, which is found outside of the thyroid. This includes (R):

  • Type 1 deiodinase, which generates T3 for circulation, is found in the liver and kidney.
  • Type 2 deiodinase converts T4 to T3 within the cells of the brain, pituitary, and brown fat tissue.
  • Type 3 deiodinase, found in the placenta, brain, and skin, leads to the generation of rT3

Carrier proteins bind to most thyroid hormones, leaving only a very small fraction available. These include thyroxine-binding globulin (TBG), albumin, and thyroid binding prealbumin (R).

Thyroxine Binding Globulin is made by the liver (R).

  • 99.97% of T4 is bound, and 0.03% is free.
  • 99.7% of T3 is bound and 0.3% of T3 is free.

T3 and T4 and the Immune System

Immune cells have receptors for T3, and administration of T3 increases the size and growth of cells in the thymus (R).

In mice, T4 treatment suppresses antibody synthesis and growth of white blood cells (R).

However, in a cell-based study, T4 potentiates rabbit lymphocyte to grow, while T3 suppressed it (R).

Both T4 and T3 enhanced interferon-induced (stimulated) natural killer cells but were ineffective at the baseline natural killer cell activity (R).

TNF-alpha and interferons induce production of class I and II HLA antigens in human thyroid cells (thyrocytes), which cause autoimmunity, as patients with autoimmune thyroid disorders have increased HLA class I and II antigens. The thyroid cells themselves produce IL-1 and IL-6 (R).

The immune system is weakened with stress, making the body more receptive of autoimmune (a condition where the immune system attacks itself) thyroid conditions (eg, Hashimoto’s thyroiditis) (R).

Too much physical stress may trigger potentially fatal thyroid problems in those with prior thyroid insufficiencies, such as untreated hyperthyroidism or Graves’ disease (R).

Human lymphocytes, when stimulated by toxin from the bacteria Staphylococcus, produce an immunoreactive TSH-like substance. Macrophage stimulated with LPS also produces TSH. While typically TSH production in the pituitary is inhibited by T3 hormones, this production of TSH in the immune cells is not (R).

TRH and TSH Fluctuates with the Circadian Rhythm

TSH is lower during daytime and increases at night around the time we go to sleep. Our biological clock (suprachiasmatic nucleus or SCN) communicates with cells that produce TRH in the hypothalamus. However, T3 and T4 fluctuate much less than TSH, perhaps because they take much longer to produce and degrade in the blood (R)

In depressed people, the nighttime TSH surge doesn’t happen. In addition, this fluctuation of TSH is abnormal in certain other diseases (R).

In healthy men, leptin and TSH fluctuate similarly over 24 hours. The fluctuation of TSH was not observed in men who are deficient in leptin (R).

Nerve cells that control TRH production and release have receptors for a-MSH (R).

Stress Elicits Thyroid Problems

Mental stress triggers the release of cortisol, which can increase thyroid hormone production (R).

The immune system is weakened with stress, making the body more receptive of autoimmune (a condition where the immune system attacks itself) thyroid conditions (eg, Hashimoto’s thyroiditis) (R).

Too much physical stress can trigger potentially fatal thyroid problems in those with prior thyroid insufficiencies such as untreated hyperthyroidism or Graves’ disease (R).

Winding down mentally through sleep or meditation and light exercise to increase endorphins (hormones to make the body feel happier) helps with thyroid conditions (R).

Surgery or Other Medical Treatments Combat Serious Thyroid Malfunctions

Thyroid hormone as a treatment to substitute a faulty gland’s hormones and to prevent further growth of thyroid tissue especially in those with thyroid cancer to prevent the return or advancement of the cancer (R).

Hypothyroidism, a condition where not enough of the correct thyroid hormones are produced, by disorders such as Hashimoto’s disease where the thyroid gland is not properly operating. Common treatments are to eradicate the current gland with surgery or radiation. Thyroid hormone replacement will be employed subsequently (R).

The Body Attacks its Own Thyroid Factors in Thyroid Autoimmunity

Thyroid Autoimmunity occurs when the body creates particles (called antibodies, etc) that, though normally is supposed to attack foreign substances, attacks the body’s own thyroid hormone (R).

Often, people with the thyroid receptor beta gene will develop an autoimmune disease (R, R2).

An autoimmune disease (AD) against thyroid hormones will exhibit a rise in TSH (a hormone by the pituitary gland which triggers the release of T3 and T4 from the thyroid) levels in the blood (R).

In addition, the thyroid hormones then regulate the release of growth-related factors (IGF-I and IGFBP-3) (R).

A common related AD is Hashimoto’s Thyroiditis (HT), where the thyroid gland is attacked by the bodies’ antibodies (R, R2).

HT leads to too little thyroid hormones being created because the thyroid gland is being attacked (R).

In Grave’s Disease, too much thyroid hormone is created because antibodies produced against the thyroid hormone receptor block places on them that TSH inhibitors were originally supposed to bind to stop T3 and T4 production bind (R).

Hyper/Hypothyroidism Causes Digestive Problems

Sometimes, absorption of T3 and T4 become abnormal in the small and large intestines (major thyroid hormone holding tanks). Too much T4 (a characteristic of hypothyroidism) overly limits thyroid hormone absorption. The liver returns some T3 and T4 from the blood back into the gut via its chemical secretion, bile. T4 and T3 directly returns to the gut via abdominal blood circulation (R).

Specific digestive diseases may be associated with autoimmune thyroid processes, such as Hashimoto’s thyroiditis and Grave’s disease. In the esophagus, thyroid hormone excess leads to faster contractions. Thyrotoxic (too much thyroid hormone in the body) patients report symptoms of fullness, lower-abdominal pain, oral gassiness, tachygastria (faster electrical pacemaker action in the stomach than normal), throwing up, less electrical pacemaker activity in their digestive tract and hypergastrinemia (results in the excess of stomach acid), which all may affect how food is pushed along the digestive tract. Slight appetite increase and slight diarrhea (because fat reabsorption in the body is weakened) occurs. All of these secondary symptoms of hyperthyroidism forces the liver to work harder and may lead to liver tissue scarring over time. Treatment for hyperthyroidism can cause hypothyroidism (underproduction of thyroid hormones) and prevents the body from gaining as much energy from food in addition to difficulty swallowing in severe cases, constipation, and a decreased appetite (R, R2).

Histamine and Thyroid Hormones Affect The Amount of the Other Present

A study found that newly- born rats used their thyroid hormones to regulate the number of neural mast cells, which release histamine as an inflammatory immune response (R).

Histamine decreases T3 and T4 for a short amount of time (15 to 30 minutes) (R).

Histamine can regulate how 3-iodothyroacetic acid (produced by the breakdown of thyroid hormones) breaks down particles into energy (R).

Higher Thyroid Hormone Levels Led to Higher Cognitive Function

For women and African Americans, increased levels of free T4 in the blood correlated with enhanced ability to see the relationship of objects in space. A higher total T4 count coincided with higher speeds between thinking about an action and ability to perform that action in people without elevated depressive symptoms (EDS). Men with higher free T3 and T4 in the blood had better language and verbal aptitude. Higher T3 absorption, for whites, demonstrated higher speeds between thinking and doing and enhanced ability to see the relationship between objects in space. Overall, higher free T4 levels was related to faster speeds of transmitting signals to muscles and visual-spatial skills while a lower TSH level was related to faster speeds of transmitting signals to muscles and higher focus (R).

Thyroid hormones regulate nervous system-related growth. In particular, the central nervous system (which consists of the brain and spinal cord) needs T3 and T4 to upkeep normal development. A drug, L-T4 (which consists of T4), when administered to rats, enhanced spatial memory (R).

While fixing thyroid problems may help normalize mood and cognitive ability, a severe hypothyroidism cognitive failure will not be completely cured (R).

Subclinical hyperthyroidism (an elevated level of TH with a decreased level of TSH) and higher free T4 within the normal range may cause decreases in thinking ability (R, R2).

Increased total T3 count was related to lower overall cognitive ability in people with mild cognitive impairment. Those with higher than average total T3 counts had trouble with remembering, visuospatial skills, planning, and emotional regulation. Lower total T3 in patients showed cognitive ability equal to those without thyroid disorders (R).

Based off of studies in rats, T3 along with electroconvulsive shock therapy may be a viable alternative to lithium with electroconvulsive shock therapy because the lithium treatment has shown cognitive damage in patients (R).

The body maintains thyroid hormone concentrations within a strict range. Aging changes these concentrations. Because aging and thyroid hormone level changes are simultaneous, studies suggest that hormone changes and cognitive decline are correlated. In those the euthyroid (those with normally-functioning thyroid glands) individuals aged between 61 and 79 years may be more affected by differences in T4 (the actual hormone) than TSH (stimulates the production of thyroid hormones). In those above 80 (euthyroids), TSH concentration increases compared to thyroid hormones, possibly as an evolutionary advantage as thyroid hormones have the role of breaking down components in the body for energy, which the very elderly would not need (R).

Thyroid Hormones Obstructs Sleep

Sleep deprivation leads to increases in thyroid hormone activity. In this way, the hormone may inhibit sleep (R, R2, R3).

A full day of no sleep caused a 1.5 times increase of T4 to convert into T3 (levels of T4 stayed the same in the study) (R).

Half a typical dose of sleep deprivation led to higher levels of TSH in the blood; this elevation continued for another day (R).

Patients with obstructive sleep apnea, though rarely caused by too little thyroid hormone in the body, who undergo hormone therapy often show improvement. Those with no thyroid disorder do not improve from such therapy for sleep apnea (R).

Hypothyroidism Increases Severity of Mood Disorders

Hypothyroidism in adults cause mild anxiety in mice. T3 is suggested to lower the sensitivity of the part of the brain that makes hypothyroid test subjects anxious (R). More T4 in the body corresponds to less severe anxiety. More severe panic attacks were associated with higher TSH levels (R).

Major depressive and anxious-depressive women showed lower T3, T4, and TSH levels than their non-depressive female counterparts. Furthermore, these depressive women showed less sensitivity to TSH (R).

More T4 and Less T3 May Indicate Severity of Depression

Depression can accompany thyroid problems. The mental disorder, in turn, adds further abnormalities such as high T4 levels, low T3, high reverse T3, a blunted TSH response to TRH (chemical signal that triggers TSH), positive antithyroid antibodies, and high TRH (in the spinal fluid) concentrations. Those on antidepressant drugs report elevated positive response to antidepressants when simultaneously coupled on thyroid hormone therapy. Dysphoria, anxiety, irritability, emotional lability, and lack of focus are common mental disorders following hyperthyroidism. The older, affected with overly high levels of thyroid hormones, appear to experience a depressive-like condition. Anxiety is also prevalent among thyrotoxicosis.

Hypothyroid patients experience depression-like conditions. The lower TSH levels were from the normal state, the more severe the depressive conditions. T4 seems to be ineffective as treatment. Conversely there is some evidence that more T4 and less TSH  are found in those with deeper depression due to thyroid problems. In those with only depression, low T3 and high reverse T3 levels were observed (R, R2).

Infections Lower Thyroid Activity

The body enters a state of rest by slowing production of thyroid hormones to decrease bodily levels of energy extraction from food sources when fighting an infection (a condition called non-thyroid illness syndrome or NTIS), however, this state may prove disadvantageous when not enough energy is taken for the muscles, which leads to failure of muscle-dependent body processes like breathing (R).

Hyper and hypothyroidism have both been associated with weakened ability to detoxify free radicals that enter the body (oxidative stress). NTIS displays oxidative stress, supporting the idea that this condition is a mechanism of immunity in addition to being a condition of hypothyroidism (R).

Cytokines Stop Actions When Dealing with the Thyroid

Cytokines, part of the hypothalamic-pituitary-thyroid system, is primarily to stop actions during euthyroid sick syndrome and AITD (autoimmune thyroid disease) (R).

Cytokines that inhibit responses can signal for additional T cells (which are immune cells from the thyroid) to help fight off an infection (R).

Weight Loss and T3 Levels

Weight loss follows treatment for hypothyroidism (of which weight gain is a symptom, although much of this loss may be only water when the patient is treated with L-T4. Those with higher fat contents contain higher levels of TSH and T3 (R, R2, R3).

Severe weight loss after hypothyroidism showed signs of a decrease in total T4 and free T3 but an increase in reverse T3. NTIS patients showed a decreased sensitivity of TSH to TRH and even, more rarely, reduced thyroid-binding proteins (which means a reduced ability for thyroid hormones to perform actions) (R).

Infections Cause Lower T3 Levels

When a mouse is infected, after food consumption, it will contain 75% less T3, T4, and liver nuclear T3 receptors when compared to uninfected mice. Mice that have not eaten but are infected showed a stagnation in the normal rise of reverse T3 levels when the mice did not eat (R).

Because the pituitary gland stops producing TSH to stimulate thyroid hormone secretion, T4 is converted into T3 more intensely during serious infection. Less thyroid hormone in the body translates to less extensive energy extraction from food molecules, which means there would be less energy wasted for the body. Regular TSH levels reboot after the infection (R, R2).

Fatigue Causes a Drop in Thyroid Hormones

Thyroid dysfunction is likely the reason behind fatigue (R).

General fatigue and fatigue due to strain are associated with lower free T4. Physical fatigue was associated with lower T3 (R).

Severe Pain Raises T3 and T4 Levels

Thyroid diseases are not thought to cause tendinopathies (tendon disease) and tendons tears. New research indicates the presence of thyroid hormone receptors in tendons and their possible role killing off tendon cells isolated from tendons (R).

Pain signals that reach the brain from any injury in the peripheral nervous system activate three releasing hormones in the hypothalamus. Thyroid releasing hormone(TRH) is one of three. These three releasing hormones, in turn, cause the anterior pituitary to release other hormones including TSH to the thyroid gland, which release into the serum hormones necessary for pain control including triiodothyronine (T3), and thyroxine (T4). Since normal blood hormone levels usually mean that the patient’s pain is not extreme, there would be less need for immediate intense treatment. Hormone levels return to equilibrium after the pain has passed (R).

Thyroid Hormone Receptors and Their Genes Can Lower the Risk of Cancers

Thyroid hormone receptors may be useful as tumor suppressors (R, R2, R3).

Incorrectly formed thyroid hormone receptors might lead to acute erythroleukemia (immature red and white blood cells crowd out the body) and sarcomas (connective or nonepithelial tissue cancers). If the thyroid hormone receptor beta gene is not as involved in making thyroid hormone receptors, there is a higher prevalence of breast, lung, and thyroid cancers (R).

Thyroid Hormones Can Combat Heart Problems

Thyroid hormone therapies have been considered as a treatment for hypothyroid patients with weak blood flow because T3 can make heart contractions harder as well as make arteries wider so that more blood can pump through (R).

Overt hyperthyroidism induces a state of a faster heart rate, enhanced left ventricular (LV) systolic (blood pressure when heart beats) and diastolic (blood pressure when heart rests) function, and increased prevalence of supraventricular tachyarrhythmias (overly rapid heart rate originating in the lower chambers of the heart) – especially atrial fibrillation (irregularly quick heart rate that causes poor circulation), whereas overt hypothyroidism is characterized by the opposite changes. Subclinical hyperthyroidism is associated with increased heart rate, reduced exercise performance, and increased risk of cardiovascular mortality. Subclinical hypothyroidism is heart rate problems and an enhanced risk for atherosclerosis (fat buildup in the arteries) and myocardial infarction (heart attack).  L-thyroxine (L-T4) or 3,5-diiodothyropropionic acid administered in a timely manner to these patients reverses almost all of these symptoms (R, R2, R3).

Thyroid Hormones Increase Glucose Absorption From the Blood

Thyroid hormones increase oxygen consumption and glucose uptake because oxygen and glucose are used in providing energy for the body (R).

In rats, lower thyroid hormones correlated with lower levels of insulin (a storage hormone for glucose) (R, R2).

Thyroid hormones encourage protein breakdown and glucose exchange throughout cells and insulin (R).

Type 2 diabetes by thyroid dysfunction can be attributed to insulin resistance (R).

T3 may be a viable treatment for type 2 diabetes because it improved insulin production and communication with other chemical signals in mice (R).

Hypothyroidism Leads to Too Little Skeletal Development While Hyperthyroidism Leads to Too Early Development

Hypothyroidism in children leads to delayed growth, while thyrotoxicosis makes bones mature so quickly that children’s bones fuse before the child is ready. T3 builds up bone mass but also can break down bones in adults to increase new bone growth (R, R2, R3).

T4 and T3 supplements can be used for hypothyroid children to grow the bone they had not in the lack of thyroid hormone (R).

Lack of TSH may be one of the reasons for bone loss in patients who formed their bones under too much thyroid hormone (R).

T3 May Be Used To Heal Dermal Injuries

Hypothyroidism leads to yellowed, pale, scaly, and dry skin. Hyperthyroidism leads to thinning (but not wasting away) skin resulting from autoimmunity (R).

Topical T3 quickened skin tear restoration because it stimulated keratinocytes (cells that produce keratin, which gives skin an elastic characteristic) and fibroblasts (cells that allow the skin to heal itself). T4 treatments have also been suggested as a topical ointment but changed hair growth and coloration in tested cows (R, R2, R3).

Thyroid Hormones Make Mitochondria More Efficient

Mitochondria, which are responsible for powering the cell by breaking down chemical compounds into energy, which is an action thyroid hormones control by stopping the energy extraction (R). This is beneficial because sometimes, the energy extracted is wasted as heat. Thyroid hormones increase the efficiency of the process.

T3 in the mitochondria, early in the organelle’s life, makes sure it forms correctly (R).

T3 may mollify mitochondrial wear and improve mitochondrial function in those cells with defective mitochondria (R).

Fewer Thyroid Hormones Contribute to a Longer Lifespan

Lower thyroid function and TSH levels are related to longer lifespans (R, R2).

Hypothyroidism becomes increasingly prevalent with age (R).

Thyroid dysfunction- overt and subclinical, is related to heart-related death (R, R2).

In those with healthy thyroid glands, lower free thyroid hormones (within the normal range) was correlated with a higher chance of any type of health-related death, especially liver cancer (R).

Older age was correlated to less T3 and free T4 (R).

Higher levels of free T4 was related to lower levels of liver tissue scarring (R).

In older men, lower free T4 and reverse T3 concentrations correlated with higher physical ability (R).

Thyroid Supplements Benefit Athletes

When the body is overworked, unnecessary cells (at the moment) decrease activity in converting molecules into energy stop to save energy. Too much overworking will lead to increased cytokine (molecules which signal others) levels while decreasing secretion of insulin (which stores glucose) and the breakdown rate of fats. TSH may be an indicator of controlling these fats and sugars. Because the hypothalamus normally regulates these changes, repeated overworking will cause the hypothalamus to become less sensitive to changes in the body and lead to fatigue and poor performance, which would lead to the development of slow muscle fibers (R).

There is speculation that thyroid supplementation to athletes improves their performance. However, experts are leaning both ways, though those who dispel this idea are more popular in number. Thyroid hormone supplements for athletes may prevent or treat thyroid gland damage from intense training (R, R2, R3). A few experts believe that more T3 and T4 may slightly increase physical ability (R).


  • Thyroid hormones combine with retinoic acid receptors, vitamin D receptors, and PPARs (R)
  • For example, both psychological stressors and metabolic stressors from starvation have been shown to cause a decrease in TRH production levels within the PVN (R1, R2)
  • In a genetic network analysis, hub (highly connected) genes that are most connected to thyroid hormones include CREB, thyroid hormone receptors (THRA and THRB), AP-1 (Jun and Fos), STAT-3, and Nf-kB (R)

Irregular Thyroid Hormones?

If you have not yet tested your thyroid hormones, I recommend that you ask your doctor for it. If you already have your blood test results and you’re not sure what to make of them, you need to check out Lab Test Analyzer. It does all the heavy lifting for you. No need to do thousands of hours of research on what to make of your various blood tests.

People don’t realize that their blood test results contain a gold mine of information that’s waiting to be unearthed. Unfortunately, not everyone has the time or the inclination to sift through dozens of research papers.

It’s super-simple so that even if you don’t have any background in science, you will understand what your results mean, and what you can do to get them in the optimal range.

Lab Test Analyzer gives you up-to-date scientific information about your lab results. In addition, you will get both lifestyle tips and natural solutions to help you optimize your health. You can also rely on our science-based Optimal Ranges to prevent potential health issues and maximize your overall wellbeing.

All of the content is backed by science and researched by a team of PhDs, professors, and scientists.

We’re all unique, so we deserve solutions that treat us that way.

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  • Dylan

    Sometimes people have high RT3, and still cannot tolerate t3 by itself.

    If cortisol is within acceptable ranges as is iron, and free t4 isn’t above range, (and inflammation isn’t too high: ESR/CRP/Ferritin), then paradoxically the person needs pure t4, and once they work there way up enough, possibly an additional 1-2 mcg of t3.

    This is for people wit HPA-axis dysfunction, that can’t seem to tolerate thyroid hormone. You still need it, but what you take, and how much is the tricky part.

    Let me know if this sounds like you.

  • Johanna David

    I have a question what if the person is already removed her thyroid hormones what will happen to her?

  • Thud

    A friend has thyroid problems; In 15 years no Doctor has been able to properly adjust the medication properly ! She has had less side effects with Armour thyroid medicine . Here skin is softer and the rash is clearing.

  • Amber Wiest

    Very well written and educational. Great job and thank you for the information!

  • Jason

    I’m appears that high TSH with low T4 free, but high T3 free if known as “pooling” of T3, according to the STTM website. It always that the real cause is low serum iron (which i already know i had super low ferritin, but moderate serum) and/or needed up cortisol levels.

    To be with honest, i don’t think doctors know what to do besides give you through hormones. It’s pretty rare for someone to find an endo that’s willing to check ALL your vitamin and mineral levels to see what your real problem is, before supplementing with through hormones. I heard levothyroxine and/or synthroid is the most prescribed drug in America. Lame af.

  • Mary

    Hi. I think it is better to be with dairy-free diet.
    If your Tsh is less than 10 It is better for you to be without any medicines. Wish you good health

  • Allison Boyle

    Hi there. I was just reading through comments and seen yours and wondered if it wasn’t too much trouble if you knew what to supplement with for low cortisol.?
    Had cortisol and thy panel done and cortisol is practically dead.
    Any help if you have spare time would be much appreciated.

  • Jason

    Wondering if anyone knows why my TSH is elevated, always 8 or 9 something…. likely due to my free T4 being on the low end of the acceptable range (0.8 ng/DL), however my free T3 looks great at around 3.9 pg/mL.

    My reverse T3 is also very low, so should I even bother taking synthetic T4 just to bring the TSH down? … or is the TSH not really that important. Most doctors I’ve seen will ONLY test TSH and free T4… not even considering the free T3 and reverse T3 (which I had to order myself from private labs). My last endo finally tested me for antibodies, which showed TPO ab’s in the mid-300’s…. but after cutting out gluten, my numbers dropped down to the 180’s. My TSH, free T4, & free T3 all stayed in the range I mentioned above. Should I just ignore the TSH and watch my free T4 and free T3? Or should I try to get the free T4 up as well? So confusing….

  • Olti

    I am sorry to hear people not getting better after treatment. It seems like you are having worse hypothyroidism symptoms and the cause is likely the treatment. Usually it is given T4 that in some people may make them worse. I suggest you to read the “CT3M handbook” and discuss it with your doctor. It suggests a treatment with pure T3. Good luck.

  • cynthia l laskowski

    I have had hashimtos for 30+ years & have not used thyroid medication for the last 10 years- The meds caused increased severe inflammatory body pain & reduced energy so I stopped. I didnt neglect my disease & monitored my levels yearly & took supplemental tyrosine & glandulars keeping all TSH t3 free t3 t4 in norm range unfortunately both antibodies never budged & were always near the 1000 mark. About 2 years ago, I started getting rapid heart rate activity & gained 30 lbs in a months time. all markers still in the norm range, except I was told I am going through menopause & was sent to a cardiologist to monitor heart. Heart is in great shape & my symptoms of rapid heart rate are more often now in addition to the scary episodes of not being able to catch my breath. My sensitivity to food has increased where if I eat fast release foods like bread or rice, seems to set off the symptoms, so I am afraid to eat now. After reading, I notice that TSH rises at night- which is when my increased heart rate symptoms start. After my last severe episode of 100 beats per minute from 11pm til 6 am I went to the Emergency room thinking I was having a heart attack. My Tsh was at 10 during this episode. I had a CT scan & they have found nodules on my thyroid (which I have to have ultra sound on now) I guess my reason for writing my experience, is that all the doctors I have seen (for which I owe thousands of dollars to now) I still have no direction & explanation to my extremely debilitating episodes. If I were to make my own assumptions, seems I am hopping from Hypo to Hyper thyroidism & am desperate for some help. Has anyone else experienced these type of symptoms? thanks!

  • Carla

    Huh? :The last sentence makes zero sense to me: “Thyroid dysfunction is likely the reason behind fatigue (R). General fatigue and fatigue due to strain is associated with lower free T4. Physical fatigue was assoicated with physical fatigue (R).”

    1. Helen

      Hi Carla, sorry for the confusion! We’ve fixed the sentence now. It should say “Physical fatigue was associated with lower T3”

  • Poornachandra Sridhar

    Hello I want to send my Thyroid blood reports which I have got done over period of time for your help in letting me know the healthiness of myself. I am not taking any allopathy treatment but taking Indian Ayurveda treatment for the same. How to attach the Excel data file please. I am from Bengaluru, India

    1. Helen

      Hi, you can contact Joe at or over at

  • Therese Souza

    You state this in your article. “A higher total T4 count coincided with higher speeds between thinking about an action and ability to perform that action in people without Ehlers- Danlos Syndrome (a condition that lowers joint capacity).” I checked the reference and the EDS in the reference is “elevated depressive symptoms (EDS)”.

    1. Evguenia Alechine

      Hi Therese,
      Thank you for your comment. We apologize for the mistake. It’s already fixed now!

  • Monique

    Ask for a thyroid ultrasound. Tell the ultrasound tech the doctor is looking for cysts, scarring and size. Thyroid should be 2.5 centimeters on each side. Anything larger shows the thyroid is being stimulated too much by TSH, because it is not functioning well enough. Scars can happen from too much stimulation overtime because of the thyroid not functioning well enough. Same thing for cysts. Possible Hashimoto’s? Ask the doctor for a nuclear thyroid uptake scan. This will show if there are any active cells in the thyroid. Hashimoto’s can kill off your thyroid and result in very few active cells. TSH will still be normal with Hashimoto’s. Have all of your antibodies checked for Hashimoto’s. My thyroid doctor told me that the thyroid levels from blood tests show the thyroid hormone that is floating around in your blood. This doesn’t mean your body is using the thyroid hormone. Thyroid hormone can be floating around and your blood and not getting used by your body. There is no way of testing how much of the thyroid hormone is being used by your blood. That is why he goes off symptoms as well. You can have normal thyroid levels and your body not taking in the thyroid hormone and using it for energy for the cells. This is usually when a person has cellular resistants and needs T3 medication, Cytomel. The thyroid gland produces T4 hormone. It is for molecules of thyroid hormone. The body breaks one of these molecules off and it is only the T3 hormone that can enter cells . Only use name brand medication. They are coated so that they pass into the duodenum where they cross over into your blood. The generics are not coated with the enteric coating and they start dissolving in your throat as soon as you swallow them. The medication needs to crossover in the duodenum, past the stomach to be able to cross over into your blood system. If you do need T3 medication because your body is not breaking down the T4 hormone into a T3, then you will also have insulin resistance. Look up the symptoms for insulin resistance. Insulin resistance also makes it almost impossible to lose weight. Do you get shaky and crabby if you need to eat? Extremely sleepy right after eating? Need something sweet after you eat? Fatigue after working out? Cannot regenerate energy as quick as normal people? Wake up with achy restless legs? My doctor says he will start people on Metformin when their A1C is in the fives. An A1C of 6 or higher is diabetic. When someone has cellular resistance and insulin resistance symptoms, he will start them on 500 mg of metformin each day to get the body to recognize the insulin and start using it. Metformin will make your cells recognize the insulin and start using it so you will have more energy. It also will make your liver stop producing glucose constantly, sugar, to bind to all of the extra insulin floating around in your blood. The extra insulin that is in your blood is what causes the achy legs and tired after eating. He said metformin only lasts 4 to 6 hours so he eventually gets the patient up to the metformin three times a day. Start with getting the ultrasound and the thyroid uptake scan. Search on the internet for good thyroid doctors near you. So many thyroid doctors don’t believe in cellular resistance and the need for T3. Just keep going to doctors until you find one. Even paying $300 for the first visit is worth a lifetime of good health. Being hypothyroid and fat sucks and restrict lifestyle. Believe me, I know.

  • Rachael Shayna Nelson

    Make sure they look at a problem in your Thyroid too

  • Kim

    You answered your own question. Your lacking cortisol- which you need to recover from an physical injury including working out. Cortisol is what dampens inflammation and gives you energy along with other hormones. If your almost flat lined on a cortisol test you need to back off working out for a while and supplement to aid in healing..

  • Yulia Orme

    You have a wrong info. You mentioned that T3 is thyroxine and T4 is triiodothyronine, its not! T4 is thyroxine and T3 is triiodothyronine…

    1. Nattha Wannissorn

      ya it’s a typo. Corrected. Thanks.

  • Travis

    Can you tell me why I have all the symptoms of hypothyroidism, but when I got my thyroid checked everything appeared normal?

    The doctor screwed up testing my free T3, but tested TSH, T3, T4, free T4, and it all looked in the normal range. He also tested reverse T3 and that was high but at the edge of the normal range.

    I’ve also had trouble losing weight in the past. Where I was basically working out for 6 days a week. 5 hours of martial arts a week, 1 hr 5 days a week, and then lifting weights 2 days a week for about an hour. I also use to count calories regularly and rarely cheated. I went from 205 to 180 in about a year, but ended up cutting calories to about 1700 (about 1g of protein per pound, no junk food) a day and still couldn’t lose weight, was feeling like crap so I tried a low carb diet. The weight melted off. I went from 180 to 160 in about 7 weeks. I was also able to eat about 2500 calories per day. I was taking a fat burner as well and that probably helped a bit but I’ve tried the fat burner on a regular carb diet and it didn’t seem to have much affect. Sure I lost a few extra pounds but that was it. Nothing like what I lost before.

    So I’m trying to find info on why someone can have problems losing weight while eating carbs and working out regularly, but they can eat more on a low carb diet and lose weight while working out the same.

    My other hormones were tested as well. T was normal, my estrogen was low, my DHEA was high, and I did the 4 salivary cortisol test and my cortisol was low and the bump that’s suppose to happen at night happened during the day and was barely a curve. Although the high DHEA and low Cortisol was probably from overtraining. As at the time of the tests, I hadn’t done martial arts or worked out regularly for awhile. Started again by doing light weighs and high reps with light weight DBs 1 hour in the morning and 1 hour in the night. I was just trying to burn some calories and jump start my body. After a few weeks though I felt like crap and no matter how long I rested (rested several weeks without working out) I still felt the same. That’s when I went to the doctor and ran all those tests on my thyroid and hormones. He just diagnosed me with adrenal fatigue and recommended an adrenal supplement. It sort of worked. But I think it may have been the high vitamin C and he several forms of vitamin C that did it.

    I just want to get back into shape now. I’m out of shape though, more now than ever, and I weigh too much to do a low carb diet like before. I’d like to know why carbs affect me so much. Why I can’t eat many calories without gaining weight even when working out 6 days a week. I think a normal guy should be able to eat at least 3500 calories as a maintenance when working out that much. Why am I stuck around 2k calories and having low recovery? Doesn’t make sense.

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