Common symptoms
- Palpitations, racing heart, or irregular heartbeat
- Unintended weight loss despite a normal or larger appetite
- Heat intolerance and excessive sweating
- Anxiety, irritability, and restlessness
- Tremor, usually in the hands
- Difficulty sleeping
- Frequent or looser bowel movements
- Muscle weakness, especially thighs and upper arms
- Eye changes in Graves': grittiness, bulging, double vision
- Lighter or absent menstrual periods
Which labs matter
| Test | What it shows |
|---|---|
| TSH | Low or fully suppressed in hyperthyroidism; the most sensitive screening test. |
| Free T4 and Free T3 | Raised in overt hyperthyroidism; normal in subclinical hyperthyroidism. |
| TSH receptor antibodies (TRAb / TSI) | Positive in Graves' disease; distinguishes it from thyroiditis and nodular causes. |
| TPO antibodies | Often positive in Graves' too; less specific. |
| Thyroid uptake scan or ultrasound | Separates Graves' from toxic nodules and thyroiditis when antibodies are inconclusive. |
| Full blood count and liver tests | Baseline and safety monitoring for antithyroid drugs. |
Causes of an overactive thyroid
Graves' disease is the most common cause: antibodies stimulate the TSH receptor, driving continuous hormone production. Other causes include toxic multinodular goitre and single toxic adenomas, thyroiditis with temporary hormone leakage, excess thyroid hormone medication, and iodine or amiodarone exposure.
Distinguishing these matters because thyroiditis is often self-limiting and does not need antithyroid drugs, whereas Graves' and nodular disease do.
Treatment routes
Antithyroid drugs — methimazole or carbimazole, and propylthiouracil in specific situations such as the first trimester of pregnancy — reduce hormone production and are usually given for 12–18 months in Graves'. Relapse after stopping is common. Beta blockers are frequently added early to control palpitations and tremor while the drugs take effect.
Radioactive iodine permanently reduces thyroid tissue and usually results in lifelong hypothyroidism requiring levothyroxine. It is generally avoided in pregnancy and in active moderate-to-severe thyroid eye disease.
Thyroidectomy gives rapid, definitive control and is chosen for large goitres, suspected malignancy, severe eye disease, or when drugs and radioactive iodine are unsuitable. It also results in lifelong levothyroxine treatment.
Thyroid eye disease
Graves' can affect the tissues around the eyes, producing grittiness, redness, swelling, bulging, and sometimes double vision. Smoking substantially increases the risk and severity, and stopping smoking is one of the most effective things a patient can do. Active eye disease influences treatment choice and needs specialist ophthalmology input.
What to track on treatment
Hyperthyroid treatment overshoots easily — patients often swing towards hypothyroid symptoms as the dose takes effect. Tracking heart rate, weight, tremor, sleep, and heat or cold intolerance alongside each lab result makes the swing visible early, and gives your clinician the pattern between blood tests.
- Resting heart rate and any palpitation episodes
- Weight, appetite, and bowel changes
- Anxiety, tremor, and sleep quality
- Eye symptoms: grittiness, pressure, double vision
- Antithyroid drug dose, plus any sore throat, fever, or jaundice — which need urgent review