Lithium and Thyroid Disease: How It Affects Your Thyroid and What to Do About It

Lithium is one of the oldest and most effective treatments for bipolar disorder. For decades, it’s helped people stabilize their moods, prevent manic episodes, and reduce the risk of suicide. But for many, that benefit comes with a hidden cost: thyroid problems. If you’re on lithium, your thyroid isn’t just a background detail-it’s something you need to watch closely, every step of the way.

Why Lithium Messes With Your Thyroid

Lithium doesn’t just affect your brain. It also interferes with how your thyroid gland works. The thyroid makes hormones that control your metabolism, energy, weight, and mood. Lithium disrupts this process in several ways. It blocks the thyroid from releasing stored hormones like T3 and T4. It stops the gland from using iodine properly to make new hormones. It even changes the structure of the proteins inside thyroid cells that hold these hormones together.

As a result, your thyroid can’t do its job. That’s why up to 32% of people on long-term lithium develop thyroid issues. About 79% of those cases are hypothyroidism-when your thyroid doesn’t make enough hormones. Another 30-59% develop a goiter, which is a swollen thyroid that can cause neck tightness, trouble swallowing, or just a visible lump.

Women under 60 are at higher risk. Studies show they’re more than three times as likely as men to develop hypothyroidism on the same lithium dose. Age also matters. The longer you take lithium, the higher your chances. After 10 years, nearly half of users have thyroid changes.

Hypothyroidism: The Most Common Problem

If your TSH (thyroid-stimulating hormone) climbs above 4.0 mIU/L, that’s a red flag. Many people on lithium see their TSH jump from normal levels (like 1.8) to 8.7 or higher within a year or two. Symptoms are easy to miss because they overlap with bipolar symptoms: fatigue, weight gain, brain fog, depression, cold intolerance.

What’s tricky is that these symptoms often get blamed on the bipolar disorder itself. That’s why so many people suffer for months-or years-without realizing their thyroid is the real issue. One patient on Reddit shared: “My TSH went from 1.8 to 8.7 in 18 months. I was exhausted all the time. My psychiatrist said it was just my mood cycling. I didn’t get tested until I collapsed at work.”

The fix is usually levothyroxine, a synthetic thyroid hormone. But here’s the catch: people on lithium often need higher doses than others. Studies show they may need 20-30% more levothyroxine to get their TSH back into range. Why? Because lithium keeps interfering with how the body uses the hormone.

And it’s not always simple. Some patients report feeling worse even after their TSH looks “normal” on paper. That’s because thyroid hormone levels don’t always reflect how you feel. Weight gain, dry skin, and low energy can linger. That’s when you need to look beyond TSH-check free T3 and free T4 levels too.

Hyperthyroidism: Less Common, But Dangerous

Less than 5% of lithium users develop hyperthyroidism. But when it happens, it’s often misunderstood. Most cases aren’t Graves’ disease-the autoimmune condition that causes overactive thyroid. Instead, it’s painless thyroiditis. That means the thyroid gets inflamed and leaks stored hormones into the blood. It’s temporary. Symptoms like rapid heartbeat, weight loss, or anxiety usually fade on their own in 3-6 months.

The danger? Mistaking it for Graves’ disease. If you’re given antithyroid drugs like carbimazole for painless thyroiditis, you could end up with hypothyroidism after the inflammation clears. The right approach? Monitor, wait, and avoid drugs unless symptoms are severe.

There’s one rare but terrifying risk: stopping lithium suddenly. If you’ve had lithium-induced thyroiditis, abruptly stopping lithium-even through dialysis for overdose-can trigger thyroid storm. That’s a life-threatening surge of thyroid hormones. One documented case involved a patient who went into thyroid storm after hemodialysis for lithium toxicity. It’s rare, but it’s why you never stop lithium cold turkey without medical supervision.

How It Compares to Other Mood Stabilizers

Not all mood stabilizers hurt your thyroid the same way.

- Valproate: Can cause mild TSH spikes in 5-10% of users, but rarely leads to full hypothyroidism. - Carbamazepine: Almost no thyroid impact. - Lithium: Highest risk by far. 20-32% develop thyroid dysfunction. Lithium’s edge? It’s better than the alternatives at preventing suicide. One study showed a 14% absolute reduction in suicide attempts compared to other mood stabilizers. That’s huge. But that benefit comes with a trade-off: lifelong thyroid monitoring.

What You Need to Do: Monitoring and Management

The American Thyroid Association says: test before you start lithium. Then every 6 months for the first year, then yearly after that. Don’t skip these. TSH levels can creep up slowly. Many doctors miss it because they wait for symptoms.

Here’s a simple checklist:

• Before starting lithium: TSH, free T4, and thyroid antibodies (TPOAb)
• Every 6 months for the first year: TSH and free T4
• After year one: TSH annually, or more often if levels change
• If TSH rises above 4.0: check free T4 and consider levothyroxine
• If you develop a goiter: get an ultrasound

Don’t panic if your TSH is slightly high in the first 3 months. It can take 6-8 weeks for lithium to fully affect the thyroid. Many primary care doctors misread this and stop lithium too early. One 2022 study found 23% of patients had lithium discontinued unnecessarily because of early TSH spikes.

New Hope: Selenium and Future Treatments

There’s promising research on selenium. A 2023 trial gave 100 mcg of selenium daily to people on lithium. After two years, hypothyroidism dropped from 24% to 14%. Selenium helps the thyroid process iodine and reduces inflammation. It’s not a cure, but it’s a low-risk, low-cost way to lower your chances.

There’s also new lithium-like drugs in development. RG101, currently in Phase II trials, looks like it stabilizes mood just as well as lithium-but without raising TSH. That could change everything.

What Patients Are Saying

On Reddit, 68% of users on lithium reported thyroid issues. Most said they felt better once they started levothyroxine. But many also said they wished their psychiatrist had warned them sooner.

One person wrote: “I’ve been on 900mg for 8 years. My thyroid is fine. But I’ve seen friends struggle. No one told me this could happen.”

Another said: “I take 75mcg levothyroxine. My TSH is normal. But I still feel tired. I think my doctor just stops looking once the numbers are ‘okay.’”

And one of the most common positive comments? “Better than the alternative. My bipolar symptoms are controlled, even with thyroid issues.”

That’s the reality. Lithium isn’t perfect. But for many, it’s the best tool they have. The key is managing the side effects, not avoiding the drug.

When to Consider Alternatives

You don’t have to stay on lithium forever. If your thyroid problems are severe-like persistent hypothyroidism despite medication, or repeated goiter growth-it’s fair to talk about switching. Alternatives like valproate or lamotrigine may be options, especially if you’re not at high risk for suicide.

But don’t switch just because your TSH is slightly high. Talk to your psychiatrist. Get a second opinion. Lithium’s benefits for long-term stability and suicide prevention are unmatched. Don’t give it up unless you have a better, safer plan.

Final Thoughts

Lithium and thyroid disease aren’t a dealbreaker. They’re a partnership you need to manage. The thyroid problems are real, predictable, and treatable. But only if you’re watching for them.

Get your labs done. Track your symptoms. Ask for free T3 and T4 if you’re still tired. Consider selenium. Don’t panic over small TSH changes. And never stop lithium on your own.

This isn’t about avoiding lithium. It’s about using it wisely-with your thyroid in mind.