TSH levels are important in determining thyroid health 2. TSH (thyroid stimulating hormone) is a hormone that the pituitary gland produces in varying amounts in order to stimulate the thyroid gland to produce hormones called thyroxine (T4) and triidothyronine (T3). Normal levels of TSH range from 0.4 to 4.0 mIU/L. TSH levels above 4.0 are considered high and result in a diagnosis of hypothyroidism. These high TSH levels occur when the pituitary produces more than normal amounts of TSH because the thyroid lags to produce T4 and T3.

Early Onset Symptoms

When TSH levels reach 2.0 mlU/L, the risk of developing hypothyroidism increases. At these levels, the condition is often called sub-clinical hypothyroidism. During sub-clinical hypothyroidism, patients may suffer subtle symptoms that are often attributed to normal factors, such as growing older or stress. These symptoms might include fatigue and mild depression.

Varying Symtpoms

The severity and combination of symptoms experienced with high TSH levels varies greatly from one patient to another. Some may suffer from just a few symptoms, while others seem to have every symptom when they experience high TSH levels. Because of the unpredictably of symptoms, regular blood tests are necessary to monitor TSH levels once diagnosed with hypothyroidism. Symptoms may or may not be present when levels rise.

Common Symptoms

High TSH levels can affect a person's overall outlook and mentality.

Myxedema Coma

When hypothyroidism is left untreated, it can cause myxedema coma, which is a dangerous condition that results in loss of normal brain function and even death. Myxedema coma is rare, but it is most common in women and elderly hypothyroid patients whose thyroid condition is left untreated for an extended period of time. Incendence of myxedema coma increases during the winter months and in areas of extreme cold.

Symptoms During Pregnancy

Hypothyroidism is often diagnosed during pregnancy, as thyroid levels change greatly at this time. Testing TSH levels has become a standard part of pre-natal care, as even mild hypothyroidism during pregnancy can cause:

  • pre-eclampsia
  • increased risk of miscarrage
  • anemia
  • postpartum hemorrhage
  • fetal cardiac dysfunction
  • low birth weight
  • even impaired development of brain function

Pregnant women, especially those with a history of thyroid issues, are encouraged to have their TSH levels monitored closely.


Hypotonia is a muscle disorder that often accompanies hypothyroidism. Those who suffer from hypotonia have low muscle tone, reduced strength and are at a greater risk for ligament injury. Because people with hypothyroidism may have slowed reaction times in addition to an increased risk of hypotonia, patients should use extreme caution when participating in strenuous physical activity.