Low T3 (Triiodothyronine) – Symptoms, Causes, Treatment

Low T3 (Triiodothyronine) – Symptoms, Causes, Treatment

Before understanding everything about low T3 levels, let’s quickly go through about the Thyroid Gland in general.
The thyroid gland is a butterfly shaped gland located in the neck, in front of the voice box. The thyroid gland is larger in females than in males. It increases in size during menstruation and pregnancy.

Functions of the Thyroid Gland are:

  • Calcium Metabolism
  • Metabolism of Fats
  • Increases breakdown of proteins in the muscles
  • Promotes skeletal growth and development
  • Promotes normal development t of the brain
  • Maintaining Basal Metabolic Rate (BMR)
  • Regulation of body temperature. T4 and TSH act as a thermostat.
  • Increases rate of secretion of digestive juices.
  • Stimulates physical and mental growth and development.
  • Regulation of menstrual cycles.

Thyroid Hormones with Normal Values:

T3 – 60-181 ng/dL Free T3 – 1.4-4.4 pg/mL
T4 – 4.5-10.9 µg/dL
Free T4 – 0.8-2.7 ng/dL
TSH – 0.5-4.7 mU/L
  • Production of T4 is stimulated by the Thyroid Stimulating Hormone (TSH) secreted by the Pituitary Gland.
  • Production of T3 and T4 is stimulated by the Thyrotropin Releasing Hormone secreted by the pituitary gland. Therefore, thyroid hormones production and secretion are directly controlled by the hypothalamic-pituitary-thyroid axis.
  • T4 is inactive and does not have the ability to bind unless it gets converted into t3.
  • Majority of T4 is converted into t3 in the gut, liverkidneys and some in other tissues as well.
  • The thyroid hormones work as binding proteins for various physiological processes in the body.
  • T3 and T4 are found in circulating blood mostly bound to proteins. Free T3 is found lesser in circulation than T4.

T3 or Triiodothyronine and What Does it Do

  • T3 is a hormone secreted by the thyroid gland.
  • As discussed earlier, T4 is converted to T3. T3 increases the Basal Metabolic Rate (BMR) and increases body’s oxygen and energy consumption.
  • T3 has its action on almost all tissues of the body except spleen and testes.
  • It increases the rate of glucose synthesis or gluconeogenesis.
  • T3 is also responsible for increasing rate of synthesis of proteins.
  • T3 increases heart rate and contractions. It also increases the cardiac output.

Low level of T3 is termed as a Low T3 Syndrome, Euthyroid Sick Syndrome or Non-Thyroidal Illness Syndrome. Interestingly, low T3 levels are not entirely related to the thyroid gland.

  • The typical presentation of the euthyroid sick syndrome is low levels of T3 and TSH with raised T4.
  • There is an increased level of reverse T3.

In the intensive care unit, the amount of patients having low T3 levels is significantly high. More than 70% of the patients show low T3 levels. However, only a few patients had low free T3 levels.

Causes of Low T3 Levels:

  1. Both Primary and Secondary Hypothyroidism causes low T3 and T4 levels. Some patients may even show normal levels of T4.
  2. In patients suffering from some psychological or physical stress, T4 is excessively converted into reverse T3 (rT3).
  3. Low levels of Thyrotropin Releasing Hormones – In patients having a chronic illness and in acute infections where inflammatory cytokines suppress the production of Thyrotropin Releasing Hormones.
  4. Reduced secretion of TSH.
  5. Low calorie intake due to fasting or chronic infections.
  6. Auto Immune Hypopituitarism – The progressive destruction of the pituitary gland leading to deficiency of hormones, namely, Adrenocorticotropin (ACTH), Thyrotropin, Gonadotropin (FSH/LH) growth hormone and Prolactin.
  7. Increase in gastrointestinal lipo-polysaccharides is responsible for under-conversion of T4 to T3.
  8. Altered levels of binding proteins.
  9. Changes in function of Thyroid Receptor Hormone (TRH).
  10. Change in Thyroid Hormone Metabolism.

Symptoms of Low T3 Levels:

Since the thyroid gland is responsible for a lot of physiological functions inside our bodies, it is obvious, that even a slight alteration in its function may trigger significant abnormalities. Some of the low T3 symptoms are

Neurological Symptoms:

  • Depression and other psychological complaints
  • Poor concentration
  • A migraine occasionally
  • Poor sleep

Metabolic Symptoms:

  • Weight gain
  • Poor metabolism of nutrients and hormones
  • Over-sensitivity to cold temperatures
  • Fatigue, muscle and joint aches and pains

Dermatological Symptoms:

  • Dry skin and lusterless hair, occasionally alopecia
  • Loss of lateral eyebrows.
  • Peri Orbital Edema and myxedema

Immunological Symptoms:

Reproductive System:

  • Heavy and Irregular Menstruation (Menorrhagia)
  • Infertility in Females and Impotence in Males.

Other Symptoms Include:

Low levels of thyroid require medical attention primarily. Any signs of severe dysfunction like respiratory distress, hypertension or heavy menstruation are not to be ignored. These conditions need to be evaluated by a qualified physician.

Special care and attention need to be paid in pregnant women who have pre-existing thyroid conditions or have been diagnosed with thyroid abnormality during pregnancy.

Serial assessment of thyroid function during all three trimesters is essential to monitor thyroid levels.T3 and T4 tend to be elevated during pregnancy, but this does not require specific treatment.

However, women with pre-existing thyroid disorders may need to adjust medicine dosages as and when the pregnancy progresses.

All the natural ways to improve thyroid functioning can work hand-in-hand along with appropriate medical treatment. None of these following mentioned methods can be used to replace the on-going medical treatment.

Ways to Increase Low T3 Levels Naturally:

  1. Fresh fruits and vegetables are rich sources of anti-oxidants. These help the body to get rid of free radicals.
  2. Zinc supplements aid thyroid gland in producing thyroid hormones. Foods rich in zinc like pumpkin seeds, sea food, spinach and meat.
  3. Foods rich in iron like dates, raisins and jiggery.
  4. Vitamin B sources like fish, lean meat, milk and milk products.
  5. Regular exercise helps to break the vicious circle of fatigue-body aches-weight gain.
  6. Meditation, yoga or therapies to help you de-stress. Some amount of counselling may be required in cases of severe depression.
  7. Goitrogenic foods such as broccoli, cabbage, cauliflower and kale should be avoided preferably.
  8. Soy protein, coffee and high fiber food need to be consumed in moderation as these tend to interfere with Thyroid Hormone Metabolism. These may even interfere with the action of thyroid medications.
Medically Reviewed By
Dr. Kaushal M. Bhavsar (MBBS, MD)Assistant Professor in Pulmonary Medicine, GMERS Medical College, Ahmedabad