Thyroid symptoms: underactive and overactive compared

You are tired in a way that sleep does not fix. You have put on weight without changing much, you are cold when nobody else is, your skin is dry, your hair is thinner than it was, and your brain feels like it is running through treacle. Someone has suggested you are just busy, or that this is simply what your forties feel like.

Or the other version. Your heart races while you are sitting still, you have lost weight without trying, you are irritable and hot and cannot get to sleep, and everyone including you has decided it must be stress.

Both of those can be a thyroid problem. Both are also extremely easy to explain away, which is exactly why thyroid conditions go unrecognised for months.

What the thyroid does, in one paragraph

The thyroid is a small butterfly shaped gland at the front of your neck, below the Adam's apple. It makes hormones that set the pace of nearly everything else: how fast you burn energy, your heart rate, your body temperature, your gut, your mood, your skin and hair, your periods. Think of it as the throttle rather than the engine. Set too low, everything slows down. Set too high, everything speeds up, including the things you would rather kept still.

Two opposite pictures

Because the thyroid controls the pace, the two problems tend to mirror each other. The table below is a rough guide to the pattern rather than a self diagnosis tool, and hardly anybody has every feature in one column.

What you might notice	Underactive (too little hormone)	Overactive (too much)
Energy	Heavy tiredness, sleeping more and still exhausted	Wired but shattered, trouble getting to sleep
Weight	Gradual gain with no real change in eating	Loss despite a normal or bigger appetite
Temperature	Cold constantly, cold hands and feet	Hot, sweating more, disliking warm rooms
Heart	Slower pulse	Racing or thumping heartbeat, sometimes irregular
Mood and thinking	Low mood, slowed thinking, poor concentration	Anxiety, irritability, restlessness, a short fuse
Gut	Constipation	Looser or more frequent stools
Skin and hair	Dry skin, coarse thinning hair, brittle nails	Warm moist skin, fine hair, hair loss as well
Other	Hoarse voice, puffy face, muscle aches, heavier periods	Hand tremor, eye changes, lighter periods, muscle weakness

Both can cause a swelling in the neck, known as a goitre, and both can cause hair loss and fatigue, which is one reason the columns are far less tidy in real life than in a table.

Why these symptoms get put down to something else

Nothing in either column is specific. Tiredness, weight change, low mood and poor concentration are among the most common things anyone brings to a doctor, and they overlap with stress, poor sleep, iron levels, depression, the perimenopause and simply getting older. That overlap is genuine rather than anyone's failure.

Fatigue in particular gets shrugged off for a long time before anybody investigates it properly, and it deserves a systematic look rather than a guess. If exhaustion is your main complaint, our longer piece on how persistent fatigue is assessed and treated works through the possibilities in order.

An overactive thyroid gets mislabelled especially often, because a racing heart, sweating, tremor and a sense of dread look exactly like an anxiety disorder from the outside. Anxiety is real, common and frequently the answer, but the physical causes deserve ruling in or out rather than assuming. Our doctors treat anxiety as an ongoing condition too, and the two conversations are not mutually exclusive. It runs the other way as well: an underactive thyroid can look a great deal like low mood needing longer term support.

Symptoms suggest it, testing decides it

This is the part to hold on to. No symptom, and no combination of symptoms, confirms a thyroid problem. Thyroid function is measured on a blood test that looks at the hormone level along with the signal the pituitary gland is sending to the thyroid. That result is then interpreted alongside your symptoms, your history, the medicines you take, whether you are pregnant, and sometimes a repeat test, because one slightly unusual result can be a blip. Our page on how thyroid disorders are managed sets out what that ongoing care usually involves.

If you already take thyroid medication, never adjust it, skip it or stop it based on how you feel. Thyroid treatment is guided by testing, and feeling better is not the same as being on the right amount.

Once treatment starts the pattern is review and adjust, review and adjust, over months. Most people with an underactive thyroid stay on treatment long term and need periodic monitoring. An overactive thyroid has several treatment routes and usually needs specialist input, which is where a referral letter fits in.

When to get urgent help

Most thyroid disease develops slowly and is not an emergency. A few situations are. Seek help straight away if you have:

• A pounding, racing or irregular heartbeat that will not settle, particularly with chest pain or feeling faint.
• Chest pain or pressure of any kind.
• Marked confusion, drowsiness you cannot shake off, or someone who is difficult to rouse.
• A neck swelling that is enlarging quickly, or one that is hot and painful.
• Difficulty swallowing, a sense that your throat is closing, or noisy or laboured breathing.
• A high fever alongside a racing heart and agitation, if you are known to have an overactive thyroid.
• New or worsening eye problems such as double vision, pain behind the eye, or vision that is dimming.

Call 999 for chest pain, collapse, serious difficulty breathing or swallowing, or anyone confused or very drowsy. For symptoms that worry you without being that severe, such as a neck swelling you have just noticed or palpitations that came and went, call 111 for advice on how urgently you need to be seen. A video consultation is the right setting for the slow burning version of this, not the acute one.

How an online thyroid consultation works

A first appointment is mostly a careful history, which video handles well. You go through your symptoms in detail and when they started, your family history (thyroid conditions run in families), your medicines, and anything else that might explain the picture. If you have had thyroid results before, having them in front of you makes the conversation far more useful. The doctor can explain what they mean, and where it is clinically appropriate prescribe or write a referral letter. What happens before, during and after a consultation is set out plainly, what an appointment costs in pounds is listed openly, and you can book a thyroid review for a time that suits you.

What to have ready

• Any previous thyroid results you hold, with dates if possible.
• A list of every medicine and supplement you take, including anything containing iodine or biotin.
• A rough timeline of your symptoms. When did you last feel like yourself?
• Your weight trend, if you know it, rather than a single figure.
• Who in your family has a thyroid or autoimmune condition.

Write that timeline down beforehand. People routinely underestimate how long they have felt off, and the real answer is usually longer than what they say out loud in the appointment.

If you have been explaining away the same set of symptoms for months, that alone is reason enough to have it looked at properly. Speak to a UK registered doctor today and get a proper explanation, a plan and ongoing review, rather than another shrug and another year of feeling like this.