TSH, or thyroid stimulating hormone, is secreted by the pituitary gland and stimulates the thyroid gland to secrete two other hormones: T3 and T4. When a blood test determines that TSH is low, it means that the pituitary is releasing less TSH in an attempt to balance levels of T3 and T4 in the body.


Hyperthyroidism is the term used to describe an under-active thyroid, or a thyroid that does not secrete enough T3 and T4. In this condition, TSH levels are elevated because the pituitary begins secreting more of the hormone in an attempt to boost thyroid function 2.

Causes for Low TSH Levels

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Hyperthyroidism is most commonly caused by some form of damage to the thyroid gland itself, such as a growth or tumor, an infection or inflammation. Occasionally, hyperthyroidism may be caused by a pituitary gland that does not function properly.

Symptoms of Low TSH

The most common symptoms of low TSH include:

  • sweating excessively
  • intolerance to heat
  • shaking or tremors
  • increased heart rate
  • anxiousness
  • fatigue
  • abnormal weight loss

Treatment of Hyperthyroidism

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Treatment of hyperthyroidism varies due to the cause of the condition; however, it most commonly includes taking anti-thyroid drugs daily, which inhibit the production of T3 and T4. In severe cases, treatment may include removal or partial removal of the thyroid gland.

Controlling Thyroid Levels

In order to maintain a balance among T3, T4 and TSH, it is important to maintain regular treatment from a doctor and to have TSH levels checked regularly.