Do thyroid problems cause weight gain?

There is a complex relationship between thyroid function, metabolism, and body weight. Hypothyroidism, or an underactive thyroid, is associated with decreased metabolism, and you may experience modest weight gain (5-10 lbs) as a result. Most of this weight gain is due to excess salt and fluid retention.
If you have an underactive thyroid and are placed on thyroid hormone replacement, your ability to gain or lose weight should be the same as those without thyroid problems. Many factors may contribute to weight gain, and treatment of an underactive thyroid does not necessarily result in weight loss.
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Diseases of thyroid function: Hypothryoidism 

Weight gain and weight loss often go hand-in-hand with thyroid problems as the thyroid glands are responsible for maintaining many hormone levels within the body. Upsetting the balance of hormone level in the body can make it more challenging to maintain a given weight. 

The thyroid is one of the organs in the body that control how much energy you use. There are many diseases of the thyroid, which can cause abnormalities in the way your body uses energy throughout the day. When the thyroid is underactive, a condition called hypothyroidism, one of the effects can be weight gain or inability to lose weight. The weight gain associated with hypothyroidism is usually minimal to moderate; significant weight gain is uncommon. Other common symptoms of hypothyroidism are dry skin, fatigue, becoming cold easily and thinning hair. This condition can be diagnosed by your doctor with simple blood tests, and is treated with a pill that supplements you with the hormone that your thyroid is unable to produce.
Marjorie Nolan Cohn
Nutrition & Dietetics

The hypothalamic-pituitary-thyroid (HPT) axis area in the brain has well-known effects on metabolism function, and newer research suggests it also has a role in the regulation of food intake. Evidence suggests that the HPT axis can directly influence food intake. Thyroid dysfunction can have significant consequences on appetite and therefore body weight. These effects were thought to be controlled by thyroid hormones. However, more recently, research of the thyroid hormone in the central nervous system (CNS) shows that it may actually play an important role in physiologically regulating appetite. The major central nervous system (CNS) areas important in the regulation of appetite are the hypothalamus and brainstem. Evidence suggests that thyroid hormones may access specific regions of the hypothalamus that regulate appetite. It’s well established that the hypothalamic-pituitary-thyroid axis regulates body weight. Thyroid hormones are known to effect metabolic rate. Thyroid dysfunction can have clinically significant consequences on appetite and body weight. Hypothyroidism classically causes reduced basal energy expenditure with weight gain. And the disruption of normal hormonal balance may contribute to increased appetite or desire to eat.

Judy Caplan
Nutrition & Dietetics

They can play a role in weight gain. Generally though, most people gain weight from eating too many calories, choosing the wrong foods and not exercising enough. If you are having unexplained fatigue, heart palpitations, dry skin, and excessive weight gain, see your health care provider. He or she can run the right tests to determine if your thyroid is the cause of your weight gain.

Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
Your thyroid, the butterfly-shaped gland located in your neck right below the Adam’s apple, pumps out hormones that control metabolism throughout the body. But sometimes a medical condition called hypothyroidism occurs, which can slow down production of these hormones. As a result, the digestive process in your gut slows down, causing bloating and weight gain.

However, hypothyroidism affects only about 5% of the population. Consuming too many calories, not exercising enough, genetics, family history and unhealthy habits, such as skipping breakfast and not getting enough sleep, are the reasons behind most weight gain.

In addition to unexplained weight gain, other symptoms of hypothyroidism include dry skin, daily fatigue, and coarse or brittle hair. If you suspect you may have hypothyroidism, ask your doctor to check by performing a simple blood test.
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Amy Jamieson-Petonic
Nutrition & Dietetics

Perhaps ... I have seen a few clients with metabolic conditions in which weight gain was a side effect (such as hypothyroidism), but this test needs to be confirmed by a doctor. This test can help get to the root of the issue fairly quickly.

Thyroid problems such as hypothyroidism can cause you to be tired a lot, which means you will be less active and burn less calories throughout the day. So once you have been cleared by a physician, seek out a fitness professional that is familiar with your condition that can create a program that works best for you. One thing a fitness professional needs to consider when creating the program is the clients ability to do long bouts of exercises at one time, since hypothyroidism can cause you to feel tired and general discomfort. If you had a goal to exercise for 30 minutes a day, you may want to consider splitting that up into three 10 minutes sessions throughout the day, so you can better manage the exercise without getting too tired. From there, you can slowly work your way up to more intense exercises to help you burn even more calories.

Dr. Jack Merendino, MD
Endocrinology Diabetes & Metabolism
This is one of the most common questions I get in my regular clinical practice, and it is one of the most misunderstood and misrepresented issues in all of medicine.

The most common form of thyroid disease is hypothyroidism, meaning that the thyroid is under-active. In hypothyroidism, the thyroid gland makes less thyroid hormone than is normal, and symptoms or problems may arise from this. Some people have what is referred to as “subclinical” hypothyroidism, meaning that laboratory studies show they are hypothyroid, but they have no real symptoms. When symptoms do develop in hypothyroidism, they include fatigue and malaise, dry skin and hair, thinning of the hair, constipation and feeling cold even when other people feel comfortable. Many people find that they are not as intellectually sharp as they think they should be, and depression may occur. These symptoms improve tremendously or resolve completely when one is given thyroid hormone replacement. The most common form of thyroid hormone replacement is levothyroxine, which comes as many brands, including most commonly Synthroid and Levoxyl.

One can also have hyperthyroidism, meaning the thyroid gland is making too much thyroid hormone. The symptoms of this condition include a fast heart beat or palpitations, tremulousness, oily skin or hair, frequent bowel movements and feeling hot when other people are comfortable. When severe, hyperthyroidism often leads to weight loss, but the other symptoms are usually bad enough that the person is happy for treatment, even if the weight comes back on.

Because most symptoms of hypothyroidism are generally the opposite of the symptoms in hyperthyroidism, people often conclude that hypothyroidism leads to weight gain. In fact, this is not usually the case. Most people who develop hypothyroidism do not have significant weight gain and treating hypothyroidism usually does not result in much weight loss. If someone has suddenly gained weight without any change in what they are eating or how much they are exercising, and they are newly diagnosed with hypothyroidism, treating the under-active thyroid may help the person return to his or her former weight. Similarly, if someone has dramatically improved his or her diet or exercise habits and has not lost weight, it is reasonable to do blood tests to check thyroid function, but in most cases this does not lead to a diagnosis of a thyroid problem.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.