Your heart races for no reason, your hands shake, you sweat more easily than you used to – and the pounds are dropping even though you eat normally? That may sound like stress, but it can also be an overactive thyroid. The small gland in your neck then makes too much hormone and forces your whole body into a constant sprint. Here you'll learn how to recognize an overactive thyroid, what causes it and how it's diagnosed.
Key takeaways
- With an overactive thyroid (hyperthyroidism), the gland makes too much hormone – your metabolism runs in high gear around the clock.
- Typical signs: racing heart, restlessness, trembling, sweating, trouble sleeping and weight loss despite a normal appetite.
- The most common causes are Graves' disease and so-called hot nodules (thyroid autonomy).
- The most important screening test is TSH – with an overactive thyroid, it's typically low.
- Left untreated, an overactive thyroid mainly strains your heart and bones – so it pays to get it checked early.
What happens when your thyroid is overactive?
The thyroid hormones T3 and T4 are something like the gas pedal of your metabolism. They set how fast you burn energy, how often your heart beats, and how active your nerves and digestion are. With an overactive thyroid, the gland keeps that pedal floored – your body burns more than it should, and every system is running in overdrive.
The control center in your brain tries to counter-steer: it turns down the signal hormone TSH. That's exactly how an overactive thyroid shows up in your blood – a noticeably low TSH is usually the first clue, often before the free hormones are clearly elevated.
Symptoms: your body in a constant sprint
- Racing heart and palpitations: your pulse is high even at rest; some people feel skipped beats or an unpleasant pounding that reaches up into the throat.
- Restlessness and irritability: nervousness, an inability to sit still and mood swings – often mistaken for "stress."
- Weight loss despite a good appetite: your energy use climbs so much that the pounds drop even though you eat as much as usual, or more.
- Sweating and heat intolerance: you always feel too warm, and your skin is moist and warm.
- Shaky hands: a fine tremor of the fingers that you notice, for example, when holding a cup.
- Trouble sleeping and exhaustion: your body can't settle down – strangely, many people feel wired and drained at the same time.
- Frequent bowel movements, irregular periods, hair loss: digestion, hormone balance and hair get thrown off rhythm, too.
Good to know: in older people especially, an overactive thyroid can look different – sometimes the only signs are an irregular heartbeat such as atrial fibrillation, weight loss or weakness. Even then, it's worth taking a look at the thyroid.
Causes: Graves' disease, hot nodules and more
- Graves' disease: an autoimmune disease in which antibodies constantly push the thyroid to make hormone. Eye symptoms such as bulging eyes or a feeling of pressure are typical – but not always present.
- Thyroid autonomy ("hot nodules"): individual areas of the thyroid disconnect from the body's control and produce hormone on their own – more common in older age.
- Phases of inflammation: at the start of thyroid inflammation (including Hashimoto's), stored hormone can be released all at once – usually a temporary overactive phase.
- Too much medication or iodine: too high a dose of thyroid hormone or large amounts of iodine (for example from contrast dye) can also tip the values.
Good to know: there's a subclinical (mild) form here, too – TSH is low, but the free hormones are still normal. You can still have symptoms, and the heart in particular is sensitive to it. Whether and when to treat is an individual decision.
