High TSH and low T4: what does it mean for me?

If your report shows a high TSH and a low T4 (or low FT4), your thyroid is underactive. Doctors call this overt hypothyroidism. It sounds worrying, but it is common, it is easy to confirm, and the treatment is simple and effective. You can see how your numbers fit with the thyroid report reader.

What does this pattern mean?

The pituitary gland in the brain controls the thyroid using TSH. When thyroid hormone (T4) falls, the pituitary sends out more and more TSH to push the gland to work harder. When the thyroid cannot keep up even with this push, T4 drops below normal and TSH climbs high. In overt hypothyroidism, TSH is often well above the range, and sometimes very high.

This is the next stage after subclinical hypothyroidism, where TSH is high but T4 is still normal. Read high TSH with normal T4 to compare.

What causes an underactive thyroid?

• Hashimoto’s thyroiditis. The immune system slowly damages the thyroid. This is by far the most common cause in India, and it runs in families. Anti-TPO antibodies are usually positive.
• After treatment for an overactive thyroid, such as radioactive iodine or surgery.
• After thyroid surgery for a goitre, nodule or cancer.
• Thyroiditis after childbirth, which can cause a temporary underactive phase.
• Some medicines, such as amiodarone, lithium and certain cancer medicines.
• Iodine deficiency, now much less common in India because of iodised salt.
• Congenital hypothyroidism in newborns, which is why babies are screened soon after birth.

What symptoms can it cause?

Symptoms come on slowly, so many people get used to them. Common ones are:

• tiredness and sleepiness
• feeling cold when others are comfortable
• dry skin and hair fall, sometimes thinning of the outer eyebrows
• mild weight gain and puffiness of the face, especially around the eyes
• constipation
• heavy or irregular periods, and difficulty conceiving
• low mood, slow thinking and poor memory
• muscle aches and swelling of the legs

Some people, particularly older adults, have very few symptoms. Hypothyroidism can also raise LDL cholesterol, which often improves with treatment.

Do I need more tests?

Usually only a few. Your doctor may check:

• Anti-TPO antibodies, to confirm Hashimoto’s as the cause.
• A thyroid ultrasound, only if there is a swelling or lump in the neck.
• Cholesterol, blood count and vitamin B12, as these often travel with thyroid problems.

If both TSH and T4 are low, the problem may be in the pituitary rather than the thyroid. This is called central hypothyroidism and needs an endocrinologist. See unusual thyroid test results.

How is it treated?

The treatment is levothyroxine, a tablet form of the same T4 hormone your thyroid makes. It replaces what your gland cannot produce. It is inexpensive, widely available in India and, at the right strength, has no meaningful side effects.

Your doctor chooses the starting strength based on your weight, age, heart health and how low your thyroid is. Older people and people with heart disease are usually started more gently. TSH is then checked again after about six to eight weeks, and the strength is adjusted by your doctor until TSH is back in range. Once stable, most people need a TSH check every 6 to 12 months.

How you take the tablet matters as much as the strength. Tea, coffee, milk, calcium and iron can all reduce how much is absorbed. Read how to take levothyroxine the right way.

Is it lifelong?

In Hashimoto’s thyroiditis, and after thyroid surgery or radioactive iodine, the gland does not recover, so treatment is usually lifelong. Think of it as replacing a missing hormone, not as a strong drug. Temporary forms, such as after childbirth, may settle, and your doctor will review whether treatment can be reduced or stopped.

There is no Ayurvedic, homeopathic or herbal substitute for thyroid hormone. Some “thyroid” supplements contain iodine or animal thyroid extract, which can make things worse. Ask your doctor before taking any.

How soon will I feel better?

Many people feel more energetic within a few weeks. Swelling, skin, weight and cholesterol improve over a few months. Hair fall can briefly get worse in the first weeks before it improves, as old resting hairs are pushed out. Read hair loss and the thyroid.

Treatment usually brings only a modest weight change, mostly from losing retained fluid. If weight gain is your main concern, read can thyroid problems cause weight gain.

What should you ask your doctor?

• What is causing my underactive thyroid?
• When should my TSH be checked next?
• How should I time the tablet around tea, breakfast and my other medicines?
• I am planning a pregnancy. What changes then?

Pregnancy needs special care, because the thyroid needs of mother and baby rise early. Read thyroid problems in pregnancy. If your TSH stays hard to control, see who an endocrinologist is or book a consultation.