Hyperthyroidism is the overproduction of hormones by the thyroid gland. Metabolism speeds up: the pulse quickens, weight drops, and excitability and sweating appear. The severe manifestation of a hormone excess is called thyrotoxicosis.
The diagnosis is confirmed by tests: in hyperthyroidism TSH is reduced and the free hormones are elevated. Then the cause is determined — the treatment depends on it.
Causes
The most common cause is Graves' disease, an autoimmune condition in which antibodies stimulate the gland. Other causes: toxic nodular goiter and a toxic adenoma (nodules autonomously producing hormone), and also thyroiditis — inflammation in which stored hormone "leaks" into the blood (usually temporarily).
Symptoms
Characteristic are palpitations and skipped beats, trembling hands, sweating and poor heat tolerance, anxiety and irritability, insomnia, weight loss with a normal or increased appetite, frequent stools, and in women — scantier and less frequent periods. In older people the picture may be blurred (sometimes only an arrhythmia or weakness).
Diagnosis
The typical laboratory picture is a low TSH with elevated free T4 and/or free T3. In subclinical hyperthyroidism TSH is reduced but the free hormones are still normal. The cause is clarified by antibodies, ultrasound and scintigraphy (radioiodine uptake).
Treatment
Three main approaches: antithyroid drugs (thiamazole, propylthiouracil), radioactive iodine and surgery. Beta-blockers quickly relieve palpitations and tremor until the main treatment takes effect. The choice depends on the cause, age and comorbidities; after radioiodine or surgery, hypothyroidism often develops and requires replacement therapy.
Reference ranges
Typical laboratory patterns (the thresholds and reference ranges depend on the laboratory):
| Overt hyperthyroidism | TSH reduced, free T4 and/or T3 elevated |
| Subclinical hyperthyroidism | TSH reduced, free T4 and T3 normal |
Calculate using this marker
Calculators where Hyperthyroidism (thyrotoxicosis) is used directly:
Frequently asked questions
How does hyperthyroidism differ from thyrotoxicosis?
Hyperthyroidism is increased hormone production by the gland itself. Thyrotoxicosis is a broader concept: an excess of hormones in the body from any cause, including taking T4 preparations or a "leak" of hormone in thyroiditis without overactivity.
What is subclinical hyperthyroidism?
A state in which TSH is reduced but free T4 and T3 are still normal. Even without symptoms it can raise the risk of arrhythmias and osteoporosis, so it requires observation and sometimes treatment.