Hyperthyroidism is a condition in which the thyroid gland produces excessive amounts of thyroid hormones, resulting in increased metabolic activity. The most common causes include Graves' disease, toxic multinodular goitre, thyroiditis, and excessive iodine intake. Early diagnosis and appropriate management are important to prevent complications such as cardiac arrhythmias, osteoporosis, and thyroid storm.

Pathophysiology

Hyperthyroidism results from excessive synthesis and secretion of thyroid hormones (triiodothyronine [T3] and thyroxine [T4]), leading to increased basal metabolic rate and enhanced sympathetic nervous system activity. The underlying mechanism depends on the cause, including autoimmune stimulation of the thyroid gland, autonomous hormone production, inflammatory release of stored hormones, or excess iodine exposure.

Risk factors

• Female sex

• Family history of thyroid disease

• Autoimmune disorders

• Previous thyroid disease

• Excessive iodine intake

• Thyroiditis

• Multinodular goitre

• Thyroid nodules

• Postpartum period

• Smoking (especially in Graves' ophthalmopathy)

Diagnostic criteria

Hyperthyroidism should be suspected in patients presenting with:

• Tremors

• Excessive sweating

• Smooth, velvety skin

• Fine hair

• Rapid heart rate

• Enlarged thyroid gland

• Frequent bowel movements

Investigations

• Serum thyroid-stimulating hormone (TSH)

• Free thyroxine (Free T4)

• Baseline complete blood count, including differential white blood cell count

• Liver function tests (bilirubin and transaminases)

• Differential white blood cell count during febrile illness or onset of pharyngitis in patients receiving antithyroid medication (routine monitoring is not recommended)

• Thyroid uptake scan when thyrotoxicosis is confirmed and the underlying cause is uncertain

Management

Management depends on the underlying cause of hyperthyroidism.

Non-pharmacological management

• Provide patient education regarding the disease and treatment options.

• Advise adequate nutrition and hydration.

• Encourage smoking cessation, particularly in patients with thyroid eye disease.

• Arrange regular clinical follow-up and thyroid function monitoring.

Pharmacological management

Treatment should be selected according to the underlying cause of hyperthyroidism.

• Beta-blockers may be used for symptomatic relief of adrenergic symptoms such as palpitations and tremor.

• Antithyroid medicines, radioactive iodine therapy, or surgery are selected according to the specific cause and individual patient factors.

Monitoring

• Repeat TSH and Free T4 to assess treatment response.

• Monitor for adverse effects of antithyroid medicines, particularly agranulocytosis and hepatotoxicity.

• Advise patients receiving antithyroid medicines to seek urgent medical attention if they develop fever or sore throat.

• Continue regular clinical assessment until euthyroidism is achieved.

Complications

• Atrial fibrillation

• Heart failure

• Osteoporosis

• Thyroid storm

• Weight loss and malnutrition

• Ophthalmopathy (in Graves' disease)

Prognosis

The prognosis depends on the underlying cause and timely initiation of treatment. Most patients achieve good symptom control with appropriate therapy and regular follow-up. Delayed diagnosis or untreated disease increases the risk of cardiovascular complications, osteoporosis, and thyroid storm.