Thyroid stimulating hormone, or TSH, is produced in the pituitary gland, a small endocrine organ located in the brain. The pituitary gland produces a number of hormones, and is known as the master gland for its regulatory influence over the rest of the endocrine system. Thyroid stimulating hormone regulates the activity of another endocrine gland, the thyroid, which is located at the front of the throat. When the pituitary gland produces excessive amounts of thyroid stimulating hormone, a number of consequences can result.
Increased Thyroid Hormone
As a consequence of an increase in thyroid stimulating hormone, the thyroid gland excretes more of its own hormones, which include thyroxine, also known as T4, and triiodothyronine, or T3. T4 is the more prevalent of the two, and is released in quantities up to 20 times greater than T3, according to Gary A. Thibodeau, Ph.D., in his book, "Anatomy and Physiology." T3, however, is far more powerful than T4.
Increased Metabolism
The thyroid gland is responsible for regulating metabolism, the rate at which the body burns energy. The Merck Manuals Home Edition explains that increasing metabolism causes an acceleration in the rate at which all of the organs in the body function.
Accelerated Heartbeat, Higher Blood Pressure, Arrhythmia
The increase in metabolic rate that occurs due to excessive thyroid hormones causes the heart rate to accelerate. Blood pressure rises as well. Arrhythmia, meaning abnormal heartbeat, may also result due to the speeding up of body functions. Dr. Bahaa M. Fadel of the Division of Cardiovascular Medicine at Stanford University has stated that T3 binds to receptors on cardiac muscle cells and that in doing so increases contractility of cardiac muscle cells, causing them to shorten more rapidly. The consequences of hyperthyroidism include increased ventricular stroke volume and cardiac output, and can exacerbate any pre-existing cardiac conditions.
Heat Intolerance
Another consequence of excessive thyroid hormones is an inability to regulate body temperature. This may manifest as excessive sweating and an inability to tolerate high temperatures, according to Merck.
Goiter
The thyroid gland is the only gland that not only produces hormones, but stores them for future use. These hormones can build up within the gland itself, causing an enlargement at the front of the throat known as a goiter. An excess of TSH can prompt the thyroid gland to create more thyroid hormone than the body needs, thus causing the formation of a goiter, according to Thibodeau.
References
- "Clinical Cardiology"; Hyperthyroid Heart Disease; Bahaa M. Fadel, M.D. et al: June 2000
- The Merck Manuals Online Medical Library: Hyperthyroidism
- NetWellness: Thyroid Stimulating Hormone
- National Cancer Institute: Pituitary Tumors
- "Anatomy & Physiology"; Gary A. Thibodeau and Kevin T. Patton; 2003
