Low T3 and Weight Loss Relationship

Low T3 and Weight Loss Relationship

Thyroid hormones play a big role in growth and development.


There are two types of hormones made in the thyroid gland: T3 (Triiodothyronine) and T4 (Thyroxine.)


In focus here today is T3, the most active form of thyroid hormone, and how it plays a huge role in your current weight.


What is T3?

Containing 3 atoms of iodine, T3 is one of the thyroid hormones responsible for the many development, neural, and metabolic activities of the body.


The thyroid gland produces 20% of the total T3 in the body, with the rest being produced via the conversion of T4 to T3 through the process of deiodination in the liver and peripheral tissues of the body.


Although there are more T4 hormones in the body, T3 is more potent or more biologically active. However, it has a shorter half-life and is bound less firmly to the carrier proteins that transport the hormone around the body.


T3 Function Test

The primary diagnostic exam to determine Triiodothyronine levels is the T3 test. It measures the T3 hormone bound to carrier proteins, as well as the free hormone circulating around the body.


The T3 test is requested by the doctor if he/she suspects you to suffer from an overactive thyroid gland (hyperthyroidism) or an underactive thyroid gland (hypothyroidism.) It is also done if your pituitary gland is not producing the hormones it normally generates.


The normal levels of T3 in the body are 100 to 200 nanograms per deciliter or 1.54 to 3.08 nanomoles per liter. In pediatric patients, the ‘normal ranges’ according to doctors are as follows. Note that it is always better to be on the higher end.



Normal Range (nanograms per deciliter)

0 to 5 days

78 to 288

6 days to 2 months

80 to 275

3 to 11 months

86 to 265

1 to 5 years

92 to 248

6 to 10 years

93 to 231

11 to 19 years

91 to 218


Alterations in T3 Levels

In case your T3 levels are higher than the rates above, your physician might consider the following diagnoses:


  • Overactive thyroid gland, as in the case of Graves Disease
  • Toxic nodular goiter
  • T3 Thyrotoxicosis
  • Liver disease

Although this is the case, T3 levels might also be elevated if you are pregnant or taking thyroid medications, estrogen, or birth control pills.


Other medications that can cause a spike in T3 levels include Methadone, Clofibrate, and other herbal medications.


If you have T3 levels lower than the norm, you might be suffering from any of the following conditions:


  • Underactive thyroid gland
  • Thyroiditis or thyroid gland swelling, as in the case of Hashimoto’s disease

However, low T3 levels can also signify that you are starved or suffering from a chronic illness. Intake of the following drugs can also lower your T3 levels:


  • Thyroid medications such as Methimazole and Propylthiouracil
  • Amiodarone
  • Androgens
  • Steroids
  • Propanolol
  • Neuro-Psych medications such as Lithium and Phenytoin

Studies on the Relationship of T3 and Weight Loss

As it has been mentioned, an increase in T3 often signifies hyperthyroidism or an overactive thyroid.


In this condition, there is a heightened number of T3 hormones that affect metabolism or the body’s way of using energy. As a result, one of its profound symptoms is weight loss.


In the early days, physicians determined an individual’s thyroid function by measuring his basal metabolic rate. It was found to be increased in patients with excessive thyroid hormone levels, and decreased in those with lower levels of thyroid hormones.


As expected, with a higher level of T3, metabolic rate is increased. With a high BMR, weight loss occurs as the body uses more calories in compared to what the person is taking in.


Such effects of T3 on the cells have been the driving force behind many studies, and most of them have strengthened the link between the hormone and weight loss.


One of the oldest researches to do so is the study of Wilson and Lamberts. Published in 1981, it involved 11 obese patients who were given 25 mg of T3 supplementation with a low-calorie diet at 8-hour intervals. Results showed that the said intervention was able to increase weight loss at approximately 395 from 269 grams per day.


Showing the same positive result is the study of Koppeschaar, Meinders, and Schwarz. With obese subjects, the researchers assigned T3 supplementation of 150 micrograms daily for the treatment arm.


As expected, those who belonged in this group manifested an increase in T3 levels, alongside a decrease in the levels of T4 and Thyroid-Stimulating Hormone.


Compared to the control group, weight loss was constant in the supplemented group. Despite T3 administration, the patients did not develop hyperthyroidism or resistance to the medication.


Apart from supplementation, baseline T3 levels were also deemed to be associated with the person’s ability to lose weight. Such was uncovered in the study of Liu et al, printed in the 2017 edition of the International Journal of Obesity.


Results showed that those higher T3 at baseline showcased better weight loss. This conclusion reinforced the hormone’s role in weight regulation. As such, the difference in people’s baseline T3 levels can be one of the reasons why people lose more weight compared to others.


Thyroid Hormones for Weight Loss

Because of T3’s impact on a person’s metabolic rate, many have turned to thyroid drugs for weight loss. After all, studies have showed that 5 to 10 pounds of one’s weight can be attributed to the function of thyroid gland.


In addition, treatment of hypothyroidism – which causes weight gain – can lead to weight loss of about 10%. This is due to the fact that ‘correcting’ the condition can lead to the removal of the accumulated salt and water in the body. 


While experts say that thyroid hormones should not be used to treat obesity in patients with normal thyroid functioning, studies that support T3’s effects on weight reduction have inspired many to add the hormone to their respective regimens.


One of the drugs that have gained footing for its weight loss potential is Liothyronine, known to many as Cytomel. It is primarily prescribed to treat hypothyroidism, a condition wherein the thyroid gland is not able to produce the amount of thyroid hormones that the body needs.


Apart from that, it is also used to determine the presence of suspected hyperthyroidism in a patient.



The standard dosing for hypothyroid patients is 25 mcg per day, which can be increased by another 25 mcg every 1 to 2 weeks depending on the individual’s response to the treatment.


Given that there are no studies conducted to determine the appropriate amount of Liothyronine for weight loss, recommended doses are drawn from the experience of those who have used it for weight reduction.


Accordingly, a dose of 25 to 50 mcg daily is recommended for those men who want to make the most out of Cytomel’s effects on metabolism. Once you are able to tolerate 50 mcg for 2 days, you can increase your dose to 75 mcg to up to 100 mcg per day.


While there are those who have tried 125 mcg per day, this high a dose is not recommended by weight loss experts.


While females respond the same way as males to Liothyronine therapy, the recommended dosage is usually lower because of the fact that women have lower weights and body masses compared to men. With that being said, the suggested dose for women should range from 50 to 75 mcg per day.


While Liothyronine is effective in increasing metabolism and hastening weight loss, it has been known to lead to muscle loss, especially if taken in larger amounts. To prevent this, bodybuilding experts recommend the intake Liothyronine together with anabolic steroids at doses ranging from 300 to 500 mg per day.


Side Effects

As with other drugs, taking Liothyronine can result in a variety of side effects, with weight loss being one of them. Other events to anticipate include:


  • Temporary hair loss
  • Headache
  • Diarrhea
  • Mood changes, i.e. nervousness, irritability
  • Heat sensitivity, increased sweating
  • Menstrual irregularities

Adverse reactions such as chest pain, irregular heart rhythm, breathing troubles, fatigue, and swollen lower extremities can occur with Liothyronine intake, especially if done so in higher doses.


Should these happen, contact your physician right away.


Precautions and Reminders

Given that Liothyronine is not primarily intended for weight loss, you must be careful, should you decide to try this drug for that intention.


Here are some precautions that can help you reduce weight without jeopardizing your state of health:


  • Avoid Liothyronine if you have allergy to the said medication or other related drugs (thyroid medications.)
  • Women who are pregnant, trying to be pregnant, or breastfeeding should refrain from taking Liothyronine for the purpose of weight loss.
  • Liothyronine can interact with certain drugs and such can result to untoward medical conditions. DO NOT try Cytomel if you are taking any of the following medications for your pre-existing illness:
    • Anti-depressants or anti-anxiety drugs
    • Anti-hypertensive medications, specifically Beta-blockers
    • Anti-diabetic medications
    • Arthritis medications
    • Aspirin
    • Blood thinners, i.e. Coumadin
    • Cholesterol-lowering drugs
    • Estrogen and other contraceptives
  • Take Liothyronine 1 hour before or after taking Colestipol or Cholestyramine.
  • Store your Liothyronine in a tightly-closed container, maintained at room temperature, away from moisture or excess heat.

The most important thing to remember is this: stopping your intake of Liothyronine can result to the eventual gains of the weight you have lost.


However, this is necessary in the event that you experience the adverse reactions that have been stated above. Should this be the case, you need not fret as proper diet and exercise can help you lose the weight that you have been trying hard to get rid of.


Thyroid Hormones and Weight Gain

While an increase in thyroid hormones can lead to weight loss, you can expect the opposite with low levels of the said hormones.


With that being said, if you experience weight gain and other signs that may point to a thyroid disorder, check with your doctor so he can recommend the examinations above – and more – to accurately diagnose your condition.


And if your underactive thyroid is to blame, here are some tips that can help you cure your illness – and claim your old body back:


  • Take thyroid medications as prescribed by your physician. Note the possible side effects that can come with the intake of too much hormones, such as shakiness, nervousness, increased appetite, and inability to sleep, to name a few.
  • Eat food high in iodine, as well as other minerals that support the thyroid, namely selenium, iron, zinc, and copper.
  • Reduce the intake of food rich in goitrogens, or substances that suppress the thyroid gland. Examples include cauliflower, broccoli, and cabbage.
  • Cut back on junk food, alcohol, sugar, and gluten as they can affect proper thyroid functioning.

Thyroid hormones such as T3 play a big role in development and metabolism, among many other bodily functions.


Granted its complex relationship with your weight, it is best to keep your thyroid gland healthy with thyroid supplements such as Thyromate – so you can avoid weight gain and the other unpleasant effects of hormonal imbalance on your body.



Koppeschaar, H. P., Meinders, A. E., & Schwarz, F. (1983). The effect of a low-calorie diet alone and in combination with triiodothyronine therapy on weight loss and hypophyseal thyroid function in obesity. International Journal of Obesity, 7(2), 123-131. Retrieved September 18, 2017, from https://www.ncbi.nlm.nih.gov/pubmed/6408016.


Liu, G., Liang, L., Bray, G. A., Qi, L., Hu, F. B., Rood, J., . . . Sun, Q. (2017). Thyroid hormones and changes in body weight and metabolic parameters in response to weight loss diets: the POUNDS LOST trial. International Journal of Obesity, 41(6), 878-886. Retrieved September 18, 2017, from https://www.ncbi.nlm.th/pubmed/28138133.


T3 test. (2016, February 3). Retrieved September 18, 2017, from https://medlineplus.gov/ency/article/003687.htm


Test ID: T3. (n.d.). Retrieved September 18, 2017, from http://www.mayomedicallaboratories.com/test-catalog/Clinical and Interpretive/8613


Wilson, J. H., & Lamberts, S. W. (1981). The effect of triiodothyronine on weight loss and nitrogen balance of obese patients on a very-low-calorie liquid-formula diet. International Journal of Obesity, 5(3), 279-282. Retrieved September 18, 2017, from https://www.ncbi.nlm.nih.gov/pubmed/7275465.


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