Drug-Induced Hypothyroidism: Causes, Medications, and What to Watch For

When your thyroid slows down because of a medication you're taking, that’s called drug-induced hypothyroidism, a condition where external drugs interfere with thyroid hormone production or action. It’s not rare—many people on long-term meds don’t realize their fatigue, weight gain, or cold intolerance might be tied to their prescription, not just aging or stress. Unlike autoimmune Hashimoto’s, this type of hypothyroidism often reverses once the triggering drug is adjusted or stopped.

Some of the most common culprits include lithium, a mood stabilizer used for bipolar disorder that blocks thyroid hormone release, and amiodarone, a heart rhythm drug packed with iodine that can throw thyroid function into chaos. Even levothyroxine, a thyroid hormone replacement itself, can cause problems if the dose is wrong—too little leaves you hypothyroid, too much can mask the real issue. Other drugs like interferon, tyrosine kinase inhibitors, and some cancer immunotherapies also show up in studies as thyroid disruptors.

It’s not just about the drug itself—it’s about who’s taking it. Older adults, women, and people with a family history of thyroid issues are more vulnerable. Symptoms are subtle at first: tiredness, dry skin, constipation, brain fog. Many doctors miss it because blood tests look normal—or they assume it’s just part of getting older. But if you’re on one of these meds and feel off, ask for a full thyroid panel: TSH, free T4, and sometimes thyroid antibodies. Early detection means you can fix it before your metabolism, heart, or mood takes a hit.

The posts below cover real-world cases and science-backed insights on how medications affect your thyroid, how to spot hidden side effects, and what alternatives exist when a drug is doing more harm than good. You’ll find practical advice on monitoring, when to push back on your provider, and how to balance treatment with safety—all without jargon or fluff.