Sleep problems are often the first sign of a hyperthyroidism flare. If it’s hard or impossible to fall asleep — insomnia — your thyroid may have become overactive again. You may also wake frequently, or early, and find it difficult or impossible to fall back asleep.

Are you losing weight, but you haven’t changed your diet and exercise regimen? Or, are you eating more than usual, and not gaining weight? This could be a sign that your metabolism is in overdrive due to a recurrence of hyperthyroidism.

Hyperthyroidism causes the metabolism to speed up and can make you constantly feel hungry or thirsty. If you find yourself eating and drinking more than usual — especially without feeling satisfied — this may be a signal that your thyroid has shifted into overactivity.

Hyperthyroidism can cause noticeable changes to your skin. Skin that feels unusually smooth or velvety, and appears shinier than normal, may indicate that your thyroid is in overdrive.

Are you noticing that your pulse rate is faster than usual, especially at rest? Are you having heart palpitations or skipped beats? Is your blood pressure uncharacteristically higher than usual? Or have you had an episode of atrial fibrillation, known as AFib? These are all heart-related signs that your thyroid may be overactive.

Hyperthyroidism can make you feel warmer than usual. If you are wearing shorts and a T-shirt when everyone else is bundling up, this could be a sign of an overactive thyroid. You may also notice that you feel especially overheated after even mild exercise or exertion.

Are you feeling anxious, jittery, or nervous, but you can't pinpoint a reason why? Do you have panic attacks that seemingly come out of nowhere? The onset of anxiety or panic attacks is a common sign of hyperthyroidism.

Hyperthyroidism can cause your menstrual periods to change, becoming much shorter in length, or coming less frequently. Your flow may become noticeably lighter. Or, your periods may stop entirely when your thyroid is overactive.

There are several unusual rashes associated with hyperthyroidism. A bumpy red rash that looks like a heat rash on your face, known as miliaria, can be a sign. Another type of rash, called pretibial myxedema, appears on the shins and is a patch of rough, bumpy skin.

Are your eyes dry, scratchy, or sore, or is your vision blurry? Are you experiencing double vision? Does it appear as if your eyeballs are bulging? Can you see the whites of your eyes under your pupils? These are all eye-related symptoms that are common in a hyperthyroidism flare-up.

Some people who have radioactive iodine (RAI) treatment for hyperthyroidism disease can have a recurrence or relapse of overactive thyroid function. This is more common if you had a lower dose of RAI, or you did not become hypothyroid after RAI treatment.

In some cases, if your hyperthyroidism is being managed with antithyroid drugs, a flareup may indicate that you need an increase in the medication dosage to control your increasingly overactive thyroid.

Other factors can trigger a hyperthyroidism flare:

• You are consuming too much iodine in food or supplements.
• You were exposed to a high level of iodine in contrast used for a medical test.
• You started taking the drug amiodarone.
• You are hypothyroid, and as a result of taking an excessive dose of thyroid hormone replacement drugs you have become overmedicated.

If you have one or more red flags that you’re in a hyperthyroidism flareup, here are essential steps to take:

See your doctor to explore the possible causes and solutions of your flareup (i.e., reducing iodine exposure).

Ask for thyroid blood tests, including thyroid stimulating hormone (TSH), free thyroxine (Free T4), and free triiodothyronine (Free T3), to confirm hyperthyroidism, and determine the degree of thyroid overactivity.

If you are taking antithyroid drugs, talk with your doctor about whether you need a dosage increase — or a different hyperthyroidism treatment.

If you have a relapse after RAI, explore whether antithyroid drugs or a second RAI treatment are needed.