Thyroid Problems: Underactive vs Overactive, Symptoms and Treatment
The thyroid is a small butterfly-shaped gland at the base of the neck that produces hormones controlling the body’s metabolic rate. These hormones, mainly thyroxine (T4) and its active form triiodothyronine (T3), affect heart rate, body temperature, digestion, mood, energy and growth. When production falls or rises too far, the effects are felt throughout the body.
How the system is controlled
The pituitary gland in the brain releases thyroid-stimulating hormone (TSH), which tells the thyroid how much to make. When thyroid hormone is low, TSH goes up; when thyroid hormone is high, TSH falls. This is why TSH is the most useful first blood test for thyroid function.
Underactive thyroid (hypothyroidism)
Hypothyroidism is common, especially in women and with increasing age. The most frequent cause in countries with enough dietary iodine is Hashimoto’s thyroiditis, an autoimmune condition in which the immune system gradually damages the gland. Other causes include previous thyroid surgery, radioactive iodine treatment, some medicines such as lithium and amiodarone, and iodine deficiency.
Common symptoms
- Tiredness and sluggishness
- Weight gain despite unchanged eating
- Feeling cold
- Dry skin and thinning hair
- Constipation
- Low mood and slowed thinking
- Heavy or irregular periods
- Hoarse voice, puffy face and a swelling in the neck (goitre)
Symptoms develop slowly and are easily put down to ageing or stress.
Diagnosis and treatment. A raised TSH with a low free T4 confirms overt hypothyroidism. Treatment is levothyroxine, a daily tablet that replaces the missing hormone. It is taken on an empty stomach, usually in the morning, 30 to 60 minutes before food, and separated by several hours from iron, calcium supplements and antacids that reduce absorption. Dose is adjusted by checking TSH about six to eight weeks after any change, then yearly once stable. Most people feel much better but treatment is usually lifelong.
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Overactive thyroid (hyperthyroidism)
Here the gland produces too much hormone and everything speeds up. The leading cause is Graves’ disease, an autoimmune condition. Others include toxic nodules, thyroiditis (temporary inflammation) and excess iodine or medication.
Common symptoms
- Palpitations or a fast, irregular heartbeat
- Anxiety, irritability and tremor
- Weight loss despite a good appetite
- Heat intolerance and sweating
- Frequent bowel movements
- Muscle weakness and poor sleep
- Light or absent periods
- In Graves’ disease, gritty, bulging or inflamed eyes
Diagnosis and treatment. Blood tests show a low TSH with high T4 or T3. Antibodies, an ultrasound or a radioactive iodine uptake scan identify the cause. Treatment options include anti-thyroid drugs such as carbimazole or methimazole, radioactive iodine, or surgery. Beta-blockers quickly relieve palpitations and tremor while other treatments take effect. Untreated hyperthyroidism can lead to atrial fibrillation, bone loss and, rarely, a life-threatening thyroid storm.
Subclinical thyroid disease
Sometimes TSH is mildly abnormal while T4 remains normal. Whether to treat depends on the TSH level, symptoms, thyroid antibodies, age, pregnancy plans and heart risk. Repeating the test after several weeks is standard, because a single result can be temporarily abnormal.
Thyroid nodules and cancer
Thyroid lumps are common, and the great majority are benign. An ultrasound assesses their features, and a fine needle biopsy is used for suspicious ones. Thyroid cancer is uncommon and, in most types, highly treatable.
Pregnancy and the thyroid
Thyroid hormone is vital for fetal brain development. Women with known thyroid disease should discuss medication before conceiving, as doses often need increasing early in pregnancy.
Living with a thyroid condition
Take medicines consistently, keep appointments for blood tests and tell your doctor if you notice return of symptoms. Be wary of supplements marketed as thyroid boosters, as some contain iodine or hormone and can cause harm.
When to see a doctor
See a doctor for a persistent neck swelling, trouble swallowing, unexplained fatigue, weight change, palpitations or mood change that is not improving. Most thyroid disorders are simple to diagnose and treat once identified.
This article is for general information and is not a substitute for professional medical advice. If you are worried about your health or have symptoms, speak to a doctor or other qualified health professional.