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

When you’re taking lithium for bipolar disorder, the goal is simple: keep your mood stable. But for many people, that stability comes with an unexpected cost - your thyroid. Lithium doesn’t just affect your brain. It quietly interferes with how your thyroid works, often without warning. By the time symptoms like fatigue, weight gain, or cold intolerance show up, your thyroid may already be struggling. The good news? You don’t have to live with it. With the right monitoring and management, you can keep both your mood and your thyroid in check.

How Lithium Disrupts Thyroid Function

Lithium doesn’t cause thyroid disease outright. Instead, it messes with the natural process of making and releasing thyroid hormones. Your thyroid uses iodine to build T4 and T3 - the hormones that control your metabolism, energy, and body temperature. Lithium blocks two key steps: it stops iodine from attaching to tyrosine (a building block of thyroid hormone), and it prevents the thyroid from releasing the hormones it already made. Think of it like jamming a lock - the keys are there, but you can’t turn them.

Over time, this leads to two main problems: goiter and hypothyroidism. Goiter means your thyroid gland swells up as it tries harder to produce hormones. About 30% to 59% of people on long-term lithium develop a noticeable goiter. Hypothyroidism - when your thyroid doesn’t make enough hormone - affects roughly 20% of lithium users. In one 2023 study of over 1,200 patients, 32% developed thyroid issues, and nearly 8 out of 10 of those were hypothyroid.

It’s not just about hormone levels. Lithium also changes the structure of thyroglobulin, the protein that holds thyroid hormones in place. It even interferes with tubulin, a protein that helps thyroid cells function properly. These changes can cause the gland to grow and become less efficient. The result? A thyroid that’s working overtime but delivering less.

Who’s Most at Risk?

Not everyone on lithium gets thyroid problems - but some people are far more likely to. Women under 60 are at the highest risk, developing hypothyroidism more than three times as often as men on the same dose. Age matters too. The longer you take lithium, the higher your risk. Studies show that after 10 years, about half of patients develop goiter. And it’s not just time - dose plays a role. Each extra 100 mg per day increases your odds of thyroid dysfunction by 27%, according to a 2024 study.

Where you live also matters. In places like Denmark, where iodine intake is lower, goiter rates hit 50%. In the U.S., where salt is iodized, the rate is closer to 30%. This shows that your environment interacts with lithium in ways doctors are still learning to predict.

There’s also a genetic component. Some people develop antithyroid antibodies - signs of autoimmune activity - after starting lithium. While not everyone does, those who do are more likely to develop lasting thyroid problems. Still, research is mixed. Some studies show a clear link to autoimmunity; others don’t. The bottom line: if your thyroid starts acting up, it’s not your fault. It’s a known side effect of a powerful medication.

Hyperthyroidism on Lithium: Less Common, But Still Dangerous

Most people on lithium develop hypothyroidism. But about 3% to 5% experience the opposite - hyperthyroidism. This usually isn’t Graves’ disease. Instead, it’s painless thyroiditis: the thyroid gets inflamed, leaks stored hormones, and causes temporary symptoms like rapid heartbeat, weight loss, or anxiety. It often resolves on its own within 3 to 6 months.

But here’s the catch: stopping lithium suddenly can trigger a dangerous spike in thyroid hormones. There’s only one documented case of thyroid storm - a life-threatening surge of thyroid hormone - after a patient had lithium removed via dialysis. That’s rare, but it shows why you never stop lithium on your own, even if your thyroid is acting up.

If you do develop true Graves’ disease (which is rare), you’ll need antithyroid drugs like carbimazole. But for most cases of lithium-induced hyperthyroidism, the best treatment is patience - and monitoring.

Monitoring: What You Need to Do

You can’t manage what you don’t measure. That’s why thyroid testing is non-negotiable for anyone on lithium. The American Thyroid Association says you need a baseline TSH and free T4 test before starting lithium. After that, test every 6 months for the first year, then annually if things are stable.

But here’s what many doctors miss: it takes 6 to 8 weeks for TSH to rise after lithium starts. If your doctor panics at a slightly elevated TSH after 4 weeks, they might overreact. A 2022 JAMA study found that 23% of primary care doctors wrongly stopped lithium because of early, temporary TSH changes. Don’t let that happen to you. Wait. Test again. Let the pattern emerge.

Also, don’t rely on TSH alone. Some patients have normal TSH but low free T4 - meaning their thyroid is struggling even if the brain signal looks okay. That’s why both tests matter.

Managing Hypothyroidism While Staying on Lithium

If you develop hypothyroidism, you don’t have to quit lithium. Most people can stay on it - and take levothyroxine to replace what their thyroid can’t make. Dosing starts at 25 to 50 mcg per day, then gets adjusted based on TSH levels.

But here’s something surprising: people on lithium often need 20% to 30% more levothyroxine than others with the same TSH level. Why? Because lithium interferes with how the body uses thyroid hormone. Your cells may be resistant to it. So even if your TSH looks normal, you might still feel tired, cold, or heavy.

That’s why symptoms matter as much as numbers. If your TSH is 4.5 and you’re still exhausted, ask your doctor about raising your dose - even if it’s still in the “normal” range. Many patients report feeling better when their TSH is kept below 2.5 while on lithium.

And yes - some people still feel off even with perfect labs. Fatigue and unexplained weight gain are common complaints. That’s not always your fault. It’s the lingering effect of thyroid disruption. Don’t give up. Keep working with your team.

What About Other Mood Stabilizers?

If thyroid problems are getting too hard to manage, you might wonder: could another medication work better?

Valproate (Depakote) has a 5% to 10% risk of thyroid issues - mostly mild TSH spikes that don’t need treatment. Carbamazepine barely affects the thyroid. But here’s the trade-off: lithium is still the most effective at preventing suicide and keeping mood episodes away. A 2017 meta-analysis showed it reduces any mood episode by 39% compared to placebo. No other mood stabilizer comes close.

And it’s not just about mood. Lithium is the only medication proven to reduce suicide attempts by 14% compared to alternatives. That’s huge. For many, the thyroid side effects are worth it.

Still, if you’re struggling with constant fatigue, weight gain, or frequent lab changes, talk to your psychiatrist. Maybe you’re a candidate for a different drug - or a combination. But don’t assume the alternative is easier. Each has its own risks.

New Hope: What’s Changing in 2026

Research is moving fast. A 2024 study introduced a predictive tool that uses your age, gender, baseline TSH, and other meds (like gabapentin) to estimate your risk of thyroid decline. It’s 82% accurate - meaning doctors can now spot high-risk patients before problems start.

Another promising area: selenium. A 2023 trial gave 100 mcg of selenium daily to lithium users. After two years, hypothyroidism dropped from 24% to 14%. Selenium helps protect the thyroid from oxidative stress - something lithium seems to worsen. It’s not a cure, but it’s a simple, low-risk addition many doctors are now recommending.

And in the future? A new lithium-like drug called RG101 is in Phase II trials. Early results show it stabilizes mood just as well - but without raising TSH. If it works, it could change everything.

What Patients Are Saying

On Reddit, one person wrote: ‘My TSH went from 1.8 to 8.7 in 18 months. I’m on levothyroxine now, but my psychiatrist won’t lower my lithium dose.’ That’s a common story. Many feel stuck - grateful for mood stability but drained by thyroid symptoms.

Others say: ‘I’ve been on 900 mg for 8 years. My thyroid is perfect.’ They’re the lucky ones. But they’re the minority.

On Drugs.com, 41% of positive reviews say: ‘Better than the alternative.’ That’s the real story. Lithium isn’t perfect. But for many, it’s the best shot they’ve got at living a full life.

Final Thoughts: You’re Not Alone

Lithium and thyroid disease go hand in hand. It’s not a failure. It’s a known, manageable side effect. The key is vigilance - not fear. Test regularly. Track your symptoms. Don’t let a high TSH scare you into stopping lithium too soon. And don’t ignore your fatigue just because your labs look ‘normal.’

You’re not choosing between your mood and your thyroid. You’re learning to manage both. With the right care, you can stay on lithium - and still feel like yourself.