Low levels of TSH, or thyroid-stimulating hormone, signal a condition known as hyperthyroidism. TSH is secreted by the pituitary gland based upon a signal from the hypothalamus to stimulate the thyroid, the gland that controls metabolism. Low levels of TSH indicate that the thyroid is overactive and does not require stimulation. An overactive thyroid creates a metabolism that runs too high.
Metabolism
The thyroid gland controls the body's metabolism. It secretes T4 and T3, thyroid hormones which regulate metabolism. The hypothalamus and the pituitary gland serve as a monitor for the thyroid gland, keeping watch over the amounts of hormones secreted. When the hormones reach a low level, the pituitary gland secretes TSH which stimulates the thyroid to produce more T3 and T4. High levels of TSH indicate that the thyroid is underactive and the pituitary is trying to make it work while low levels indicate the thyroid is overactive and the pituitary does not have to secrete TSH.
Graves' Disease
Graves' disease is a disorder that causes the immune system to attack the thyroid gland. The gland retaliates by producing excessive T4 hormones. As the number of T4 hormones increases, the TSH level decreases. Scientists do not know what causes Graves' disease, according to Mayo Clinic, although it could be genetic. This condition is the most likely reason for low TSH levels and hyperthyroidism.
Enlarged Thyroid
When the thyroid gland becomes enlarged, it usually produces a lump or nodule. If the lump in noncancerous, it may begin producing too many hormones which causes the TSH level to decrease. Symptoms of a low level include a fast heartbeat, trembling and sweating. Weight and hair loss, warm skin along with a nervous feeling are other symptoms. They all reflect a speedup of the metabolism to a high level. Hyperthryroidism requires prompt medical treatment.
Thyroiditis
Thyroiditis is defined as an inflammation that causes hormones in the gland to seep into the blood. The result is the same as other conditions with too many thyroid hormones, a decrease in TSH levels.
Synthroid
Synthroid, or levothyroxine, is a synthetic thyroid hormone. It is prescribed for people who have underactive thyroids or have no thyroid due to surgical removal for a goiter or cancer. The higher the dosage of synthroid the lower the TSH level. The medicine is taken once a day, normally in the morning one hour before breakfast. A physician prescribes an initial dosage, and then a blood test within a few weeks reveals the TSH level. If the physician wants the level lower, he increases the synthroid dosage. This continues until the desired TSH level is obtained. Levels are monitored generally once a year.
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