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Tuesday, July 8, 2008

Several drugs and hormones have an effect on body weight.

Some hormones cause weight gain and others cause weight loss. Hormones that cause weight gain are of particular interest, because if researchers can study and understand how they work, they may be able to develop drugs that can interact with these hormones in a way that makes it easier for people to lose weight. Insulin is a hormone that helps turn glucose (the sugar found in food) into energy the body can use. High levels of insulin lead to weight gain, although the reason why is not fully understood. Drugs used to treat diabetes, such as insulin and medications that make the body produce more insulin, cause weight gain. Obese people often have higher levels of naturally occurring insulin than their leaner counterparts.
Female hormones, like progesterone and estrogen, are associated with weight gain. Obese women most commonly begin to gain weight after puberty, when their bodies begin to produce these hormones. Birth control pills contain estrogen and progesterone, and are associated with weight gain. Today, birth control pills cause less weight gain than in previous years because they contain lower levels of estrogen. Some women may gain more weight than usual during pregnancy, up to 110 pounds (50 kg), which may be related to differences in their hormone levels during pregnancy, as compared to other pregnant women. Women who gain excessive weight during pregnancy may never fully lose this weight. Changes in hormone levels also occur during menopause. These hormone changes lead to a change in fat distribution, including increased central obesity (fat around the midsection or waist). This fat distribution is associated with increased health risks, especially heart disease.
Thyroid hormones increase metabolism and cause weight loss. People with the disease hypothyroidism (underactivity of the thyroid gland) have a smaller amount of thyroid hormone. People with hypothyroidism are predisposed to weight gain.When these individuals are treated with a drug that contains thyroid hormones, they lose weight. Thyroid hormones are dangerous in very high levels and must be monitored closely when taken. An excess of thyroid hormones in the blood can lead to several health problems, including high blood pressure, nervousness, insomnia (trouble sleeping), menstrual cycle changes, heart palpitations (the feeling that the heart is pounding), and fever. Several hormones that may play a role in weight gain have recently been discovered. One of these is leptin, a newly discovered hormone produced in fatty tissue. Increased leptin decreases food intake and increases metabolism in rats and, according to some early studies, in humans as well. Other hormones released by the stomach—including neuropeptide Y, cholecystokinin (CCK), enterostatin, and polypeptide Y 3-36— tell the body it has consumed enough food and should stop eating. Another hormone, ghrelin, is produced by the
stomach. Ghrelin signals hunger and increases appetite.
Ghrelin concentrations increase in response to weight loss. This may make ghrelin partly responsible for people gaining weight back after a successful diet. Table 2.2 lists some of the hormones that influence body weight. Clearly, many hormones affect body weight. Some of these hormones are known, and some have not yet been discovered. By studying these hormones researchers can better understand what causes people to gain and lose weight. Eventually, researchers may be able to develop drugs that can change levels of these hormones in the body, thus giving people who are overweight or obese another weapon in the weight loss battle. Intensive study is required to identify the possible negative effects of increasing or decreasing the level of hormones in the body.