Thyrotoxicosis: the clinical, physiological, and biochemical state arising when the tissues are exposed to excess thyroid hormone

Hyperthyroidism: refers specifically to conditions in which overactivity of the thyroid gland leads to thyrotoxicosis

Aetiology

Graves disease

• Accounts for 85% of cases
• Higher incidence in females - 10:1
• Usually presents between 20-40 years
• Interacting susceptibility genes plus environmental factors

Genetic factors

• Increased incidence in family members
  • Sisters and children of women with Graves' have a 5-8% risk of developing autoimmune thyroid disease (Graves' or autoimmune hypothyroidism)
• Susceptibility associated with certain HLA haplotypes
• Polymorphisms in immune regulation associated genes e.g. CTLA-4, PTPN-22 have also been linked to Graves' disease
• There is an association with other autoimmune diseases

Other causes of thyrotoxicosis associated with hyperthyroidism

Excessive thyroid stimulation

• Hashitoxicosis - transient hyperthyroidism caused by inflammation associated with Hashimoto's thyroiditis, patient will then develop hypothyroidism
• Thyrotropinoma - TSH secreting pituitary adenoma (very rare)
• Thyroid cancer - only very rarely cause thyrotoxicosis
• Choriocarcinoma - trophoblast tumour secreting hCG

Thyroid nodules