Investigating Thyroid Function

Why focus on thyroid function tests? Investigating Thyroid Function
When to test?
Screening patients at increased risk / asymptomatic patients
Which test should be used?
Limitations of thyroid function tests
Monitoring
Thyroid tests in the pregnant patient
Sick euthyroid syndrome
Thyroid cancer
The effects of drugs on thyroid function
GP and laboratory communication
Range of tests available
Thyroid function
References
See also TSH vs FT4: Reminder May 2007

Screening patients at increased risk?

Although some patients are at increased risk of thyroid dysfunction, screening is not recommended unless there are signs and symptoms of thyroid disease. Groups at increased risk include postpartum women, and women over the age of 50. However, in some groups symptoms can be non-specific and confusing. In the elderly for instance, hypothyroidism may be confused with Alzheimer’s disease; while in post partum women, the symptoms of hypothyroidism may be confused with symptoms of post natal depression.

Patients who are likely to be at increased risk of thyroid dysfunction: 5,6
  • Patients with other autoimmune diseases (e.g. type 1 diabetes, coeliac disease)
  • Patients with dyslipidaemia (high cholesterol and/or high triglyceride)
  • Those taking some drugs, e.g. amiodarone, lithium, interferon
  • Past history of neck surgery or irradiation
  • Suspicious thyroid symptoms postpartum or a previous episode of postpartum thyroiditis
  • Chronic cardiac failure, coronary artery disease, arrhythmias, pulse >90/min, hypertension
  • Menstrual disturbance or unexplained infertility
  • Some genetic conditions (e.g. Down, Turner syndromes)

Screening asymptomatic patients

Key Point
Routine screening of asymptomatic individuals is not recommended

Routine or opportunistic screening of asymptomatic patients is not recommended. The return of positive results is low and there is controversy around the value of treatment in apparently healthy people whose only indication of thyroid dysfunction is an abnormal test result.3 While there have been several studies performed to assess the benefit of treatment in asymptomatic patients, the results are conflicting.4 Until there is clear resolution supporting the benefits of treating asymptomatic patients, screening and case finding is not recommended.


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