Reducing an overactive thyroid, known as hyperthyroidism, involves lowering the amount of thyroid hormone your body produces. This can be done through medication, radioactive iodine therapy, surgery, or dietary changes, depending on how elevated your levels are and what’s causing the problem. Most people start with medication, and treatment typically lasts 12 to 18 months before doctors assess whether the thyroid has settled into a normal range.
How to Know Your Thyroid Is Too High
Thyroid function is measured through a blood test that checks two key values: TSH (the signal your brain sends to your thyroid) and Free T4 (the hormone your thyroid actually produces). In hyperthyroidism, Free T4 is above normal while TSH drops unusually low, because your brain is trying to tell the thyroid to stop producing so much. If your doctor says your thyroid is “high,” they’re referring to excess thyroid hormone, not the size of the gland itself.
Common symptoms include a racing heart, unexplained weight loss, trembling hands, irritability, heat intolerance, and difficulty sleeping. These symptoms overlap with anxiety and stress, which is why blood work is essential for a clear diagnosis.
Antithyroid Medication
For most people, the first line of treatment is antithyroid medication, which blocks the thyroid from making new hormone. Clinical guidelines recommend staying on this medication for 12 to 18 months in adults. In children, the recommended course is longer, around 36 months. Most people notice improvement in symptoms within a few weeks, but the medication needs time to bring hormone levels fully into range.
Remission is defined as maintaining normal thyroid function for a full year after stopping medication. Relapse within that first year is common, which is why doctors monitor blood work closely during and after treatment. If hyperthyroidism returns after a full course of medication, your doctor will typically discuss more permanent options like radioactive iodine or surgery.
Radioactive Iodine Therapy
Radioactive iodine therapy works by destroying thyroid tissue so the gland can no longer overproduce hormones. You swallow a single dose, and the iodine concentrates in your thyroid, gradually shrinking it. In a study of 138 patients, a single dose cured hyperthyroidism in about 88% of cases. Effects begin within one to three months, with the full result visible at three to six months.
The trade-off is significant: radioactive iodine usually destroys enough thyroid tissue that you’ll become hypothyroid (too little thyroid hormone) afterward. The cumulative rate of hypothyroidism after treatment is about 51%, with most cases developing after the first dose. This means you’ll likely need to take a daily thyroid hormone replacement pill for the rest of your life. For many people, that’s a worthwhile exchange, since taking a single daily pill is simpler than managing an unpredictable overactive thyroid.
When Surgery Makes Sense
Surgical removal of part or all of the thyroid is generally reserved for specific situations. Doctors tend to prefer surgery over radioactive iodine when the thyroid gland is very large (above 80 milliliters in volume), when large cysts are present, or when the gland is growing behind the breastbone and compressing the windpipe. In patients whose airway was narrowed more than 35% by an enlarged thyroid, 98% experienced improvement in breathing after surgery.
Surgery is also preferred for people with moderate to severe Graves’ eye disease, since radioactive iodine can sometimes worsen eye symptoms. Like radioactive iodine, surgery typically results in lifelong thyroid hormone replacement.
Reducing Iodine in Your Diet
Your thyroid uses iodine as a raw ingredient to make hormones, so cutting back on iodine can help reduce thyroid hormone production. This is especially important if you’re preparing for radioactive iodine therapy, but it can also be a helpful supporting strategy during any treatment plan.
The biggest sources of iodine to limit or avoid include:
- Iodized salt and sea salt in cooking and processed foods
- Seafood, including fish, shellfish, sushi, kelp, and seaweed
- Dairy products like milk, cheese, yogurt, and ice cream
- Eggs, particularly the yolks
- Soy products such as tofu, soy milk, and soy sauce
- Supplements containing iodine, kelp, or dulse
Restaurant and fast food meals are difficult to control because you can’t know whether iodized salt was used. The American Thyroid Association recommends avoiding restaurant food entirely during a strict low-iodine period. Some less obvious iodine sources include commercially baked bread (which may contain iodine-based dough conditioners), red dye #3 found in maraschino cherries and some candies, and blackstrap molasses.
Cruciferous Vegetables and Thyroid Function
You may have heard that cruciferous vegetables like broccoli, kale, and cabbage can slow down the thyroid. These foods contain compounds called goitrogens that can interfere with thyroid hormone production in theory. However, a comprehensive review of the research found that normal dietary amounts of these vegetables pose no meaningful effect on thyroid function, especially when iodine intake is adequate. The handful of case reports showing a real impact involved people eating extreme, unrealistic quantities. Eating a few servings of broccoli or cabbage daily won’t meaningfully reduce an overactive thyroid.
Supplements That May Help Alongside Medication
Two supplements have shown promise when used alongside standard antithyroid medication: selenium and L-carnitine. In a clinical trial of 60 patients with Graves’ disease, the group taking 83 micrograms of selenium and 500 milligrams of L-carnitine daily alongside their medication reached remission at significantly higher rates. They also needed lower doses of their antithyroid drug overall, and their immune markers normalized faster.
The supplement combination also helped with specific symptoms, reducing the severity of tremor, irritability, mood swings, heat intolerance, and shortness of breath during exercise. These supplements didn’t replace medication, but they appeared to make it work better and faster. If you’re considering adding supplements, discuss it with your doctor first, since selenium in excess can cause its own problems.
Herbal Approaches
Bugleweed and lemon balm are two herbs with documented effects on thyroid function. Laboratory studies show that extracts from both plants can block thyroid hormone production triggered by TSH and by the antibodies involved in Graves’ disease. Case reports exist of patients managing mild hyperthyroidism with preparations containing these herbs, though the evidence is limited to small studies and individual cases. These are not substitutes for proven medical treatment, particularly in moderate or severe hyperthyroidism where uncontrolled hormone levels can damage the heart.
What Recovery Looks Like
Regardless of which treatment path you take, managing an overactive thyroid is not a quick fix. On antithyroid medication, you’re looking at 12 to 18 months of treatment before your doctor will consider stopping to see if remission holds. With radioactive iodine, symptoms start improving within weeks, but full normalization takes three to six months, and you’ll need ongoing monitoring to determine whether you need hormone replacement. After surgery, recovery from the procedure itself takes a few weeks, but adjusting your replacement hormone dose can take several months of blood tests and dosage tweaks.
Throughout treatment, expect regular blood draws every four to eight weeks to track your TSH and Free T4 levels. These numbers guide every decision about adjusting medication doses or declaring remission. The goal isn’t just to feel better, though that matters. It’s to bring your hormone levels into a stable, normal range and keep them there.