Millions of people live with hypothyroidism, and managing this condition often comes with many misunderstandings. Synthroid (levothyroxine sodium) is a prescription, man-made thyroid hormone used to treat hypothyroidism in adults and children, including infants, by replacing the hormone usually made by your thyroid gland. While Synthroid can help manage hypothyroidism, it's crucial to understand its role and limitations, especially concerning weight loss.
Synthroid: The Basics
Synthroid is a brand-name oral tablet containing the active ingredient levothyroxine, belonging to the thyroid hormone drug class. The Food and Drug Administration (FDA) has approved Synthroid for use in adults and children to treat hypothyroidism and suppress thyroid-stimulating hormones, which can help treat a certain type of thyroid cancer.
Important Considerations
- ** lifelong treatment:** Generally, thyroid replacement treatment is to be taken for life.
- Not for obesity: Thyroid hormones, including Synthroid, should not be used either alone or in combination with other drugs for the treatment of obesity or weight loss.
- Consult your doctor: Use Synthroid only as ordered by your doctor. Taking too much levothyroxine may affect your heart, especially if you are elderly or have heart disease.
Synthroid and Weight: What to Expect
Weight gain is a common symptom of hypothyroidism. Therefore, taking thyroid replacement medication like levothyroxine may reverse that weight gain. However, it’s important to have realistic expectations.
The Reality of Weight Loss with Synthroid
While levothyroxine can lead to some weight loss, it is essential to understand the context.
- Modest weight loss: According to the American Thyroid Association, when starting levothyroxine, you may lose up to 10% of your weight.
- Not a weight-loss drug: Levothyroxine should not be used to treat obesity or for weight loss.
A study in October 2013 highlighted that effective treatment with levothyroxine to restore normal thyroid hormone levels is not associated with clinically significant weight loss in most people. About half (52%) of the patients lost weight up to 24 months after initiation of treatment with LT4.
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Why Synthroid Isn't a Weight Loss Solution for Everyone
In patients with normal thyroid levels, doses of Synthroid used daily for hormone replacement are not helpful for weight loss. Furthermore, Synthroid has a boxed warning advising against using the drug for weight loss. If you don’t have thyroid function problems, Synthroid won’t help you lose weight, and using doses larger than recommended may cause serious side effects, including confusion, seizures, and coma. Synthroid overdose can even be fatal.
How Synthroid Works
Synthroid replaces or adds to your natural thyroid hormones, which are responsible for your body’s metabolism. If you don’t have enough thyroid hormones in your body, your metabolism will be slower than usual, leading to weight gain. With Synthroid treatment, your thyroid hormone level should be within a normal range. So with Synthroid treatment, your metabolism rate may be increased, and you could lose weight.
Important Precautions and Interactions
To ensure Synthroid works effectively, consider the following:
- Taking Synthroid correctly: It may take up to several weeks for you and your doctor to find the dose of Synthroid that works best for you. Then, after finding the right dose, it’s up to you to take your Synthroid the right way, every day, so that it can work properly.
- Brand name vs. generic: The FDA has determined that certain levothyroxine products are interchangeable and can be switched at the pharmacy. So, if your doctor hasn’t noted their preference for brand-name "Synthroid" on your prescription, you could get switched. In fact, 1 in 3 people who think they’re taking Synthroid aren’t.
- Take with water only: Synthroid should be taken alone, with water ONLY, on an empty stomach 30 minutes to 1 hour before breakfast.
- Food interactions: Foods containing soy and cottonseed meal can make Synthroid less effective. Walnuts, grapefruit juice, and dietary fiber can also affect the absorption of Synthroid. If you eat any of these on a regular basis, let your doctor know.
- Supplement interactions: Certain supplements can affect the way hypothyroidism treatments work.
- Dairy products: You should avoid drinking milk until at least 4 hours after taking levothyroxine. Dairy products-including milk, cheese and yogurt-contain high calcium levels, which affect how levothyroxine is absorbed into your body.
- Levothyroxine half-life: Levothyroxine will stay in your system for around 4 to 6 weeks. It takes longer for people with hypothyroidism to eliminate levothyroxine (closer to 6 weeks) than those with normal thyroid function.
Potential Side Effects
Synthroid can cause mild or serious side effects, most of which are caused by having high levels of thyroid hormones in your body. Even small changes in your Synthroid dose may cause large changes in your hormone levels, which could cause side effects.
Common Side Effects
- Shortness of breath
- Muscle spasms or weakness
- Hair loss
- Anxiety or irritability
- Trouble sleeping
- Increased appetite
- Diarrhea
- Rash
- Irregular periods in females
- Weight loss or weight gain
Serious Side Effects
- Heart problems, such as irregular heart rate or palpitations
- Heart attack
- Decreased bone mineral density
Side Effects of Too Much or Too Little Synthroid
Maintaining a consistent level of Synthroid in your body can help prevent side effects of having too much or too little of the drug in your body. To do this, it’s very important that you take your Synthroid dose regularly, once each day. And you should try to take the drug at the same time every day.
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Too Much Synthroid (Hyperthyroidism)
- Fast heart rate
- Nervousness or anxiety
- Heart palpitations
- Trouble sleeping
- Muscle weakness
- Weight loss
Too Little Synthroid (Hypothyroidism)
- Tiredness
- Constipation
- Weight gain
- Muscle weakness
- Hair loss
Dosage and Administration
The Synthroid dosage your doctor prescribes will depend on several factors, including the type and severity of the condition you’re using Synthroid to treat, your age, your body weight, other medications that you’re taking, and other medical conditions you may have. Typically, your doctor will start you on a low dosage and then adjust it over time to reach the amount that’s right for you.
Real-Life Cases
Several cases highlight the dangers of misusing thyroid hormones for weight loss:
- Case 1: A 29-year-old man was found dead after taking prescription thyroid hormone for weight loss.
- Case 2: A 50-year-old woman taking extra thyroid hormone to lose weight experienced chest pain and an abnormal heart rhythm.
- Case 3: A 32-year-old woman felt jittery after taking a dietary supplement containing thyroid hormone.
Alternatives to Synthroid for Weight Loss
If weight loss is your primary goal, consult your doctor about safe and effective strategies, including diet, exercise, and other appropriate medical interventions.
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