Toxic thyroid nodule

Thyroid nodules are extremely common and can be detected by sensitive imaging in more than 60% of the general population (1)

• often identified in patients without symptoms who are undergoing evaluation for other medical complaints
• indiscriminate evaluation of thyroid nodules with thyroid biopsy could cause a harmful epidemic of diagnoses of thyroid cancer (3)
  • screening for thyroid cancer in South Korea led to an epidemic of thyroid cancer
    • there was a 15-fold increase in diagnosis of thyroid cancer between 1993 and 2011 - the entire increase was ascribed to increase in detection of papillary thyroid cancer - there was however no change in thyroid cancer mortality
  • however inadequate selection of thyroid nodules for biopsy can lead to missed diagnoses of clinically relevant thyroid cancer
  • NICE note that evidence showed that ultrasound using established criteria is accurate for determining whether thyroid nodules need fine needle aspiration to investigate potential malignancy
    • many referrals for thyroid ultrasound are based on incidental findings of other types of imaging (for example, CT scans performed for other indications)
    • ultrasound should only be performed when a full assessment indicates a likelihood of malignancy - thyroid ultrasound of incidental findings should not be the default option because most incidental findings are not malignant and further investigation may cause harms in terms of the adverse effects of testing and patient anxiety

Notes:

• a solitary toxic thyroid nodule develops in the same way as the toxic multinodular goitre; that is autonomous change in a pre-existing goitre
• solitary thyroid nodule may be accompanied by the symptoms and signs of hyperthyroidism

Reference:

• Ospina NS et al. Thyroid nodules: diagnostic evaluation based on thyroid cancer risk assessment.BMJ 2020;368:l667.
• Ahn HS, Kim HJ, Kim KH, et al. Thyroid Cancer Screening in South Korea Increases Detection of Papillary Cancers with No Impact on Other Subtypes or Thyroid Cancer ortality. Thyroid 2016;26:1535- 40.
• NICE (November 2019). Thyroid disease: assessment and management.