The Thyroid Hormones and Body Weight Issues

As an endocrinologist specializing in both the management of persons with thyroid disorders and the mechanisms underlying complex eating behaviors, it’s not uncommon for me to hear concerns from patients, relatives, friends and others regarding body weight, in particular, concerns that a thyroid problem is either causing weight gain or preventing effective weight loss.

Many people hold such a notion. However, while it's true that abnormal thyroid hormone levels can, in some cases, contribute to body weight issues, the majority of us do not have altered thyroid hormones.

So, just how does the thyroid affect body weight, and what other hormones affect body weight and the ability to lose weight?

The relationship between the thyroid hormone and body weight affects metabolism in adults. Marked untreated, overproduction of thyroid hormone (hyperthyroidism) will often increase not only hunger and eating, but also one’s basic metabolic rate, causing more energy stores to be “burned off” than usual, resulting in weight loss despite an increased appetite.

The same can be true if someone with normal thyroid function inappropriately takes, or is given, thyroid hormone supplements, which may also increase the risk of osteoporosis, irregular heart rhythms and stroke.

On the other hand, a marked underproduction of thyroid hormone (hypothyroidism) is associated with decreased metabolic rate. Typically, the weight gain that might result in this type of thyroid issue rarely exceeds more than five to 10 pounds and is fairly rapidly resolved upon appropriate thyroid hormone replacement. Hypothyroidism also often leads to fatigue, achiness and effects on mood, which limits capacity and desire to exercise, an essential component of any weight-maintenance or weight-loss strategy.

There are other hormones produced in our bodies that influence body weight, although disorders in the production of these hormones are uncommon. One of these is the steroid hormone cortisol, which is produced by the adrenal glands (endocrine glands that rest on top of each kidney). When the body makes too much cortisol, it results in a condition known as Cushing’s syndrome. Among the many clinical symptoms of Cushing’s syndrome is obesity that presents as a rounded or “moon” face, deposit of a mound of fat in the upper back and an obese abdomen that also has wide, purplish stretch marks on the overlying skin. This condition also can arise with the chronic use of prescription steroid hormones such as prednisone, which is used to treat a variety of conditions.

Another hormone that has an effect on body weight is leptin, which is made by adipose (fat) tissue. Some of the beneficial actions of leptin include increasing the burning of fuels and decreasing food intake. Although the discovery of leptin in the early 1990s did not result in the cure of obesity due to the fact that obese individuals become resistant to the otherwise anti-obesity actions of leptin, ongoing studies are determining if yet other hormones or agents can reverse that so-called leptin resistance.

Other hormones that influence body weight and appetite include those produced by the gastrointestinal tract and nearby organs. These include glucagon-like peptide-1 (GLP-1), peptide YY (PYY) and oxyntomodulin, all produced by the small intestine. Ghrelin is produced mainly by the stomach and small intestine, while pancreatic polypeptide is synthesized by the pancreas in neighboring cells to those that make insulin.

What can be done to combat obesity?

Several prescription-only drugs that represent longacting forms of GLP-1 are now available and work to combat some of the body weight-related hormones. While the initial use of these so-called GLP-1 “analogs” is for the management of diabetes mellitus, they have also been shown to be effective in decreasing hunger and causing weight loss and are often prescribed for patients who have both diabetes and obesity.

Last December, the FDA approved one version of the GLP-1 analog specifically for the treatment of obesity, even in patients without diabetes. However, that’s not the case for most of the hormones with known effects on eating and body weight. Endocrinologists are just beginning to understand how many of these hormones work with each other, where they work and what other processes they contribute. Most of them are not yet ready for prime-time drug therapy.

However, there are other measures that can be used to control levels of these potentially obesity-producing hormones that don’t require the use of prescription drugs. For example, studies have shown that as one of the main hormones that stimulate hunger, ghrelin stimulates the appetite and often contributes to the type of increased comfort-food eating that occurs in people under stress. Ghrelin levels have been shown to stay elevated in those who get insufficient amounts of sleep, reinforcing other studies that indicate poor sleep may lead to the development of obesity. While there is no standard lab test to measure an individual’s ghrelin level, nor is there yet a pill to decrease it, these findings suggest that destressing and getting adequate amounts of sleep may go far in helping with your efforts to lose excess body weight.

Still, the tried and true mainstay of body weight control and weight loss continues to be a reduction in caloric intake and an increase in exercise. While it may be easier said than done, it’s not impossible. Evaluate your eating habits and choices – make healthier food choices and try to reduce portion sizes and snacking. Simple measures such as choosing to take the stairs instead of the escalator, parking your car a little farther away from the front door and working with your health care professional can go a long way in helping you succeed.

Some internists and endocrinologists have special interests in weight loss and can assist you with your efforts, including many with official certification from the American Board of Obesity Medicine. Plus, there are several prescription drugs that are available for weightloss management in certain cases, while weight-loss surgery is another option for more severe obesity.

Still, the best way to manage your weight is to respect your body’s needs and work on ways to get more rest and minimize your stress. Exercise goes a long way in improving mood, decreasing stress, improving general health and burning excess fuels.

Dr. Jeffrey M. Zigman is an Associate Professor of Internal Medicine and Psychiatry at the University of Texas Southerwestern Medical Center in Dallas, where he is affiliated with the Division of Hypothalamic Research and the Division of Endocrinology and Metabolism. He holds a secondary appointment in the Department of Psychiatry. Dr. Zigman’s research is geared primarily toward understanding the neuro-hormonal framework underlying complex eating behaviors, including those linked to stress and mood, with the ultimate goal of designing new methods to prevent and treat extremes of body weight and associated disorders of mood and metabolism.