The National Endocrine and Metabolic Diseases Information Service reports that approximately 5 percent of the United States population suffers from hypothyroidism. Hypothyroidism is a condition of low levels of thyroid hormones. The good news is that most patients can be treated by taking a synthetic form of thyroxine (T4 thyroid hormone), but doctors often find it difficult to find the correct dose. Taking too much of the medication will induce symptoms similar to hyperthyroidism, an overactive thyroid.
Increased Heart Rate
Thyroid hormones are able to act within all types of cells. Proteins within the cells act as receptors that attract the thyroid hormone and help to transport it into the cell. Once inside the cell, the thyroid hormones are interact with the DNA (deoxyribose nucleic acid) and stimulate the genes to produce proteins. Excess hormone causes an excess of proteins.
In the heart muscle the thyroid hormone induces the production of myosin, a protein that stimulates the cardiac muscle to contract. An increase in myosin causes an increase in contractility of the heart muscle resulting in an increased heart rate.
Nervousness
Taking too much thyroid medicine increases the levels of thyroid hormones and cause the functions of the body to speed up, according to the American Thyroid Association. This increase in hormone stimulates the central nervous system, which can cause feelings of anxiety and nervousness.
Fatigue/Sleep Disturbances
Because the body is functioning at faster speeds than normal, fatigue is common. Even though the patient may feel tired; however, they often find it difficult to fall asleep due to the increased cellular activity.
Feeling Hot
As the excess thyroid hormone stimulates the cells of the body to increase their activity, there is an increase in the production of body heat. This causes the patient to feel hot even when others around him may feel cold.
Weak Muscles
Too much thyroid medication can also cause muscles to feel weak. The muscles most often affected are those in the upper arms and legs. Many patients will find simple tasks such as standing from a squatting position or lifting heavy objects difficult to accomplish, according to the British Thyroid Organization.
