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Graves' Disease - The other side of the weight problem |
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Written by Lev Prasov
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Apr 23, 2006 at 04:39 PM |
Graves' disease is an autoimmune condition in which an antibody leads to over-stimulation of the thyroid gland and bulging of the eyes. It can effectively be treated by removing the gland or killing portions of it.
Millions of Americans want to lose weight. They diet, exercise, and take various supplements, but nothing seems to keep the weight off. There are a number of people on the other end of the spectrum. No matter what they do, they cannot gain weight. Their metabolism is active, their hearts are beating fast, and they are restless and jittery. One of the conditions that can cause this jumpstart in metabolism is Graves' disease and it is the topic for this week's DOTW.
 Figure I: The thyroid gland. Too much production of thyroid hormones from this gland results in many of the symptoms associated with Graves' disease. ( Image courtesy of the National Cancer Institute)
Graves' disease is an autoimmune disorder that primarily affects the thyroid gland (Figure I). The thyroid gland is normally responsible for regulating the body's metabolism through the secretion of thyroid hormones (T3 and T4). These hormones travel through the blood, enter cells, bind to receptors, which in turn bind to DNA and regulate the transcription of genes involves metabolism. The production and secretion of thyroid hormone is controlled by thyroid-stimulating hormone (TSH) secretions from the anterior pituitary gland. The levels of thyroid hormone in the blood are precisely controlled by loops of feedback inhibition. Thyroid hormones inhibit secretions of TSH at the level of the pituitary and one step above, at the hypothalamus. In Graves' disease an antibody that mimics TSH is produced. The thyroid gland continuously secretes thyroid hormone and the inhibition loops are lost. As a result, metabolic processes boom.
Having an overactive metabolism leads to a number of symptoms. Metabolic systems are not perfectly efficient and thus heat is generated in many of the enzymatic reactions. Due to this overheating, people with Graves' disease are often intolerant to heat and sweat profusely. Their heart rate is increased in order to supply these more active cells with more oxygen and nutrients and to get rid of the wastes. The increase heart rate puts a large strain on the heart and can lead to heart failure or disruption of the heart's natural contraction cycles (arrhythmias). With an increased metabolism, people are hungry, and yet continually lose weight. The increase in waste production and increase in food consumption can also lead to diarrhea.
There are several other common symptoms that can distinguish Graves' disease from some other metabolic disorders. The thyroid gland tends to enlarge from increased activity and can lead to the formation of a goiter. Additionally, the antibody that is produced can also bind to receptors on muscles around the eye. The binding causes an enlargement of the muscles, causing the eye to bulge forward. While many of these symptoms can point to Graves' disease, the key to diagnosis is the detection of the antibody.
Medical treatments are very effective for managing Graves' disease. The goal of most of these treatments is to reduce the production of the thyroid hormones, thus preventing the issues that result from an overactive metabolism. Antithyroid drugs, such as methimazole and propylthiouracil, block some of the processing steps that are necessary for thyroid hormone synthesis. Radioactive iodine can be used to kill off part of the thyroid gland, lowering the overall load of thyroid hormone. Additionally, surgery can be used to remove the thyroid gland altogether. With the thyroid removed, patients must be supplemented with synthetic thyroid hormones. If left untreated, Graves' disease can be life threatening. However, with these therapies most patients can lead normal and healthy lives.
For more information on Graves' disease, check out the following resources:
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DOTW 