What is TSH?

TSH is created behind the bridge of the nose, in the pituitary gland. It travels to the thyroid, where it prompts the production and release of other thyroid hormones such as thyroxine (T4) and triiodothyronine (T3), which likewise affect the production of TSH. The release of these two hormones, in turn, directs the hypothalamus to end the production of thyrotropin-releasing hormone. This tells the pituitary gland to make less TSH and keeps all the hormones at normal levels.

TSH tests are simple and widely available. The required blood test takes fewer than five minutes, is close to painless, and can be analyzed quickly. A normal TSH level is typically from .04 to 4.0 milli-international units per liter. Certain medications can affect these results, so people who take the test should inform their doctor of all of their current medications and supplements beforehand.

The removal of the entire thyroid, a thyroidectomy, prevents the body from creating the hormones T4 and T3, so people who have undergone this surgery, require thyroid hormone replacement treatments. On the other hand, TSH is often medically suppressed after a thyroidectomy prompted by cancer because TSH stimulates the growth and spread of tumors. Nonetheless, this suppression seems to have adverse effects, especially in women, vastly increasing the risk of osteoporosis development. After the removal of the thyroid, a qualified physician should regularly monitor TSH levels to prevent adverse effects further down the line.

Many factors can affect TSH tests. Other than medication, natural factors can change the results of this test. For example, if a test is administered in the morning, fasting can elevate TSH levels. Stress, pregnancy, and even the menstrual cycle can all lead to fluctuations in TSH levels, so doctors often order multiple tests.

Having too little TSH is hyperthyroidism. When this occurs, the thyroid is overproducing T4, T3, or both, which consequently tells the pituitary gland to stop producing TSH. Low TSH can also be caused by dysfunction of the pituitary gland or central hypothyroidism. In such a case, tests would also show low levels of other pituitary hormones.

The symptoms of low TSH overlap with those of hyperthyroidism since the latter is usually the cause of the former. They can include

• Insomnia and restlessness
• Muscle cramps
• Heat intolerance or sensitivity
• A noticeable increase in sweating
• A racing heart or heart palpitations

Many of these symptoms may be attributed to another cause since present with many illnesses. Testing is the best way to determine low TSH levels.

One treatment for low TSH is thyroxine replacement, which reduces the amount of thyroid hormones in the blood. Another option is antithyroid medications, which tell the thyroid to produce less T4 and T3. This will eventually increase the production of TSH. Radioactive iodine treatment can also be used to kills excessive thyroid hormone cells and is often successful with one treatment. The downside to this treatment is the possibility that it will kill off too many thyroid hormone cells, causing hypothyroidism.

High TSH levels are associated with hypothyroidism, so the two terms are often used interchangeably. This occurs when the thyroid is not making enough T4 and T3, so the pituitary gland continues to make TSH to stimulate the thyroid. Some forms of hypothyroidism or high TSH are permanent, such as when surgery completely removes the thyroid. However, high levels of TSH can also occur after pregnancy or illness and are easily rectified, sometimes even doing so on their own.

The symptoms of high TSH levels and hypothyroidism include

• Lethargy
• Weight Gain
• Chills and cold sensitivity
• Muscle Aches
• Dry Skin
• Depression or sadness

Notably, the symptoms of high TSH are often the polar opposites of those of low TSH.

The primary treatment for high TSH is synthetic T4, which will help replace the hormone of which the thyroid is not producing enough. The goal of this treatment is to raise T4 levels enough that the body directs the pituitary gland to reduce its production of TSH. Some physicians may also give a small dose of T3, since the underactive thyroid may not make enough T4 to synthesize it into T3. The danger with this treatment is suppressing TSH levels too much, which can stress the heart and cause other health problems.