Thyroid (underactive and overactive)

What is the thyroid?

The thyroid is a butterfly-shaped gland at the front of the neck that makes hormones. These hormones set the speed at which almost every organ uses energy, even the heart rate. It has two main problems:

• Underactive thyroid: The gland does not make enough hormone, and the body’s functions slow down.
• Overactive thyroid: The gland makes more hormone than needed, and the body’s functions speed up.

Both can start slowly and quietly, and it can take months or years for them to show themselves. Both are more common in women.

Symptoms

In an underactive thyroid: A lot of tiredness, feeling cold, weight gain, constipation, poor concentration, depression or low mood, dry skin and hair loss, a hoarse voice, a slow heartbeat, joint and muscle pain, and heavy or irregular periods. Symptoms come on slowly and get worse over time.

In an overactive thyroid: Weight loss despite a good appetite, a fast or irregular heartbeat, nervousness and irritability, sleeplessness, shaking hands, muscle weakness, sweating and not tolerating heat, more frequent bowel movements, and sometimes swelling at the front of the neck (goitre). In older people the symptoms are sometimes different, for example loss of appetite or withdrawal, and may be mistaken for depression or forgetfulness.

Many of these symptoms are also seen in other illnesses. So only a test can tell.

The thyroid and the rest of the body

• Blood fats: An underactive thyroid can contribute to high blood fats. That is why someone with high blood fats also has a thyroid test.
• Heart: Thyroid hormone affects the heart rate. In an underactive thyroid the heartbeat slows, and in an overactive thyroid it may become fast and irregular. An untreated overactive thyroid upsets the heart rhythm and can lead to clots, stroke and heart failure.
• Blood sugar: Diabetes (type 1 and 2) is on the list of conditions seen together with thyroid problems.
• Bones: An untreated overactive thyroid thins the bones.
• Fertility and pregnancy: Thyroid problems can affect fertility and pregnancy.
• Tiredness and weight: Because tiredness and weight change have other causes too, and symptoms alone are not enough, the doctor looks for the cause with a history, an examination and tests.

How is it diagnosed?

The doctor takes a history, examines the neck and arranges a blood test. The main test is TSH, a hormone released by the gland beneath the brain that instructs the thyroid. When thyroid hormone is low TSH rises, and when it is high TSH falls. The TSH test does not show the cause of the problem. The doctor may also ask for T4, T3, an antibody test or imaging.

The TSH result also changes in some people without thyroid disease. For example, a severe illness lowers it temporarily, after the age of 80 it may be higher, and in the first three months of pregnancy it is usually slightly lower. The result must be interpreted by the doctor alongside the symptoms and other tests.

Treatment and management

Underactive thyroid: The usual treatment is a thyroid hormone replacement tablet. This tablet makes up the hormone the gland does not make, and it is usually needed for many years and often for life. Regular blood tests show whether the dose is right. The test is repeated shortly after starting (about 6 to 8 weeks), and once the situation is stable, usually every 6 months and then once a year. A wrong dose can cause nausea, diarrhoea, headache and sleep problems. Too high a dose can harm the heart rhythm and the bones. Do not start, stop or adjust the medicine yourself.

Overactive thyroid: It is usually treatable. The options are a medicine that reduces hormone production, radioactive iodine that destroys thyroid cells, or surgery. Each method has advantages and disadvantages, and the choice depends on the cause, severity, age, pregnancy and heart disease. A hormone specialist (endocrinologist) often helps with the choice. Some medicines quickly calm the symptoms of a pounding heart and shaking but do not reduce hormone production. Medicine treatment usually takes about 1 to 2 years, and sometimes longer. After radioactive iodine treatment or surgery, an underactive thyroid may follow, and it is treated with a hormone tablet.

Follow-up and self-care

• Have your regular tests on time, even if you feel well.
• Take your medicine at the time and in the way your doctor suggests, and do not stop it without the doctor.
• Ask your doctor before taking an iodine supplement, cough syrup or seaweed, because they may contain a lot of iodine.
• Tell your doctor about all your medicines and supplements, because some medicines themselves cause an underactive or overactive thyroid.
• If you are pregnant or planning a pregnancy, tell your doctor at once.
• If you take a medicine for an overactive thyroid and suddenly develop tiredness or weakness, vague abdominal pain, loss of appetite, a skin rash or easy bruising, yellow skin or eyes, a constant sore throat, fever or chills, tell your doctor immediately.

When to get help

Call 115 (Iran’s emergency number) immediately if you have sudden chest pain or pressure that does not go away, or that comes with shortness of breath, sweating, nausea or light-headedness.

A very severe, untreated underactive thyroid rarely leads to a life-threatening state called myxoedema coma (myxedema coma), which is seen mostly in older people and needs urgent hospital treatment. An overactive thyroid also sometimes gets suddenly and severely worse (thyroid storm), and is life-threatening. If thyroid symptoms suddenly get much worse, call 115.

Talk to your doctor if you have the symptoms above, if your neck is swollen or you can feel your throat, if you still have symptoms despite medicine, or if you have developed a new symptom after taking the medicine.

Every patient’s treatment plan is different. Ask your doctor about your own situation.