The Causes Of Low Levels Of Thyroid Stimulating Hormone

The thyroid stimulating hormone is responsible for regulating the production of thyroid hormones. An imbalance in this hormone can manifest itself in the form of problems such as both hyperthyroidism and hypothyroidism.
The causes of low levels of thyroid stimulating hormone

Thyroid stimulating hormone (TSH) is a molecule that is involved in possible dysfunctions in this gland. This is why doctors ask for a test that measures the level of TSH in the blood when they perceive certain symptoms related to this organ.

A low level of TSH may indicate a change that needs to be studied further. This survey is therefore the first of many.

What is Thyroid Stimulating Hormone?

TSH stands for thyroid stimulating hormone, or technically thyrotropin. This is released by the pituitary gland after the stimulus it receives from the hypothalamus through another hormone known as a thyrotropin-releasing hormone.

When there is TSH in the blood, it comes in contact with the thyroid gland to produce two more hormones:

  • T3 or triiodothyronine. This is much more active than t4 and is the hormone that exerts the effect on the tissue. That is, it regulates metabolism.
  • T4 or thyroxine. This has minimal effect on the tissues. It is rather a reservoir of T3, since T4 can be converted to T3 when it reaches the tissue. It is T3 who performs the final action.

T3 and T4 will go to the tissue to control the metabolism of proteins, carbohydrates and fats. In addition , these hormones are very important in babies as they promote the normal development of brain tissue in a newborn baby.

The thyroid gland
The thyroid gland is stimulated by TSH, which is dependent on TRH.

Why do thyroid stimulating hormone levels in the blood decrease?

According to a study published in 2017, which included around 4,550 people aged 18 to 93 years, the incidence of hypothyroidism was 9.1%. Similarly, the incidence of hyperthyroidism was 0.8%.

Together, these two disorders affect almost 10% of the population, and it would be possible to find an abnormal TSH result in all these patients. The hormone in question is regulated in three ways:

  • The amount of TSH released by the hypothalamus.
  • The pituitary gland which is responsible for storing and releasing TSH when appropriate.
  • Negative feedback from the thyroid hormones.

What is negative feedback?

The number in the blood increases when the production of thyroid hormones is high. Both the hypothalamus and the pituitary gland detect this increase and reduce the production of TRH and TSH. This is what we mean by negative feedback.

That is, the hormones regulate themselves to maintain stable blood levels. We would have constantly entered a state of hyperthyroidism or hypothyroidism without this mechanism.

TSH levels in the blood

Normal levels of TSH in the blood are between 0.4 and 4 mIU / L. There is a disorder of the thyroid gland if these values ​​are higher or lower. 

In particular, low TSH levels mean that there is so much T3 and T4 in the blood that it causes negative feedback in the pituitary gland, which hinders production. This is commonly referred to as hyperthyroidism.

A low TSH level can also appear as a result of secondary hypothyroidism, and it occurs when there is a dysfunction of the pituitary gland, either because part of it is damaged or because something is preventing it from functioning. This could be a brain tumor, for example.

Ultimately, tertiary hypothyroidism can be the culprit. This means that the hypothalamus does not work and stops producing TRH. Therefore , it does not send signals to the pituitary gland to produce TSH.

In the first case, when there is an overproduction of peripheral thyroid hormones, there will be high levels of T3 and T4 in the blood, indicating that the metabolism is working too much. The body will therefore begin to burn all of the sugar and fat it receives to get enough energy.

Treatment of imbalances in thyroid stimulating hormone


Some of the symptoms of hyperthyroidism are nervousness, palpitations, hyperactivity and increased sweating. Hypersensitivity to heat, increased appetite and weight loss may also occur.

Talk to your doctor if you think you are suffering from hyperthyroidism. They should be able to perform blood tests to determine the level of TSH, T3 and T4. They will confirm that you have hyperthyroidism if the thyroid stimulating hormone level is low and the thyroid hormone level is high.

The causes can range from a tumor in the thyroid gland to an autoimmune disease in which the antibodies that are created overexpress the thyroid cells. There are medications that reduce and control any symptom.

Woman with thyroid problems


Symptoms in violation of the above, such as fatigue, weight gain, cold intolerance and hypothermia, are indications of hypothyroidism. You may have a brain tumor that either destroys the pituitary gland or compresses it and prevents the release of TSH. It can also be due to the low production of T3 and T4 in the gland itself.

Low levels of TSH in connection with hypothyroidism indicate a serious problem – related to the destruction of the pituitary gland. Instead, if TSH levels are normal or high, the thyroid gland may be the culprit.

Thanks for reading.

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