The pituitary gland secretes a substance called thyroid stimulating hormone (TSH) which prompts the thyroid gland to increase its production of thyroid hormone. The University of Michigan Healthcare System says that elevated levels of TSH are a sign that there is not enough of the thyroid hormone in your bloodstream. Insufficient thyroid hormone is a defining characteristic for the condition called hypothyroidism. Symptoms associated with hypothyroidism and an elevated TSH level may go unnoticed early on, but are likely to become more severe with time.
General Symptoms
According to the Mayo Clinic, symptoms of hypothyroidism vary in nature and severity depending upon the extent of thyroid hormone deficiency. General symptoms that may be associated with an elevated TSH level include fatigue or sluggishness, constipation, pale and dry skin, hoarseness, puffiness in the face, muscle aches, muscle tenderness or stiffness, unexplained weight gain, pain or swelling in the joints, muscle weakness, increased sensitivity to cold temperatures and brittle fingernails and hair. Elevated blood cholesterol levels and depression are also known to occur with abnormally low levels of thyroid hormone in the blood. Women may experience heavier-than-normal menstrual periods. If left untreated, these symptoms tend to get worse over time.
Goiter
Goiter is a condition in which the thyroid gland becomes enlarged due to constant stimulation to release more thyroid hormone. The Mayo Clinic says that Hashimoto's thyroiditis--a chronic, inflammatory autoimmune disease that destroys the thyroid gland--is one of the most common underlying causes of goiter. Goiter can lead to a noticeable enlargement of the neck area and, if the thyroid becomes large enough, it can interfere with breathing and swallowing.
Infertility and Birth Defects
High levels of TSH and low levels of thyroid hormone in the blood can impair fertility by interfering with ovulation, according to the Mayo Clinic. Additionally, infants born to mothers with uncontrolled hypothyroidism are at higher risk of birth defects, including intellectual and developmental problems.
Life-threatening Symptoms
Myxedema is a rare condition that can occur as the result of long-term, untreated elevated TSH levels. Myxedema is characterized by severe cold intolerance and profound levels of drowsiness and lethargy. Loss of consciousness may also occur. The Mayo Clinic advises that a myxedema coma can be triggered by stress or certain medications. Because this is a life-threatening condition, you should seek emergency medical care if you experience any of these symptoms.
Elevated TSH levels are also associated with an increased risk of heart disease as an underactive thyroid can cause abnormally high levels of low-density lipoprotein (LDL), or "bad" cholesterol, in the bloodstream. Even slight elevations in TSH associated with subclinical hypothyroidism (a slightly less severe, more benign version of hypothyroidism) can increase cholesterol levels, according to the Mayo Clinic. High cholesterol can force the heart to work harder to pump blood through the body, increasing the risk of developing an enlarged heart and heart failure.
