When is thyroid function testing appropriate?

When is testing not recommended?

Thyroid function tests are not recommended to be requested routinely in asymptomatic low-risk people in Australia.1 However, in the past decade, GP requests for thyroid function tests have increased by 51% (2001/02 to 2010/11). Are these tests required?

The prevalence of hypothyroidism may be up to 10% of the general population, most frequently afflicting older women.2 More asymptomatic people may have subclinical disease that can be detected through thyroid function testing. However, the value of detecting subclinical disease is unclear.

  • Subclinical hypothyroidism: elevated TSH and a normal fT4 level
    Prevalence up to 17%, especially in older women.3,4
  • Subclinical hyperthyroidism: low TSH and normal levels of circulating thyroid hormones (thyroxine and triiodothyronine).5
    Prevalence around 1% in men < 60 years and 1.5% in women < 60 years.6

There is a lack of convincing evidence that early treatment of subclinical disease will improve quality of life in otherwise healthy patients.5 It is not known if treatment will prevent development of symptomatic thyroid disease or complications associated with the disease.3,4,7 In addition, clinical trials have demonstrated that people who have normal thyroxin levels, but mild elevations of TSH often revert to normal over time.8,9 

Test people at risk or those with symptoms

It is appropriate to test people if there is clinical suspicion of thyroid function disorder, or if symptoms or risk factors are present.

Thyroid functions tests can identify thyroid dysfunction before complications develop. Consequences of untreated hyperthyroidism and hypothyroidism include:

  • atrial fibrillation
  • congestive heart failure
  • osteoporosis
  • neuropsychiatric disorders
  • symptoms that reduce functional status and quality of life.5

Who to test

It is important to recognise the risk factors, signs and symptoms of thyroid function disorder to identify people who are likely to have a dysfunction and who would benefit from testing.

Risk factors for developing thyroid dysfunction

  • Personal or family history of thyroid disease
  • Autoimmune disease
  • History of neck irradiation
  • Drug therapies such as lithium and amiodarone
  • Elderly patients and women over age 50 years
  • Women postpartum (6 weeks to 6 months)
Table 1. Signs and symptoms of thyroid dysfunction
Hypothyroidism1,2
Hyperthyroidism1
Weight gain
Hair loss
Menstrual irregularities (menorrhagia)
Goitre
Cold intolerance
Confusion
Lethargy, fatigue
Depression
Constipation
Dry skin
Weight loss (despite appetite)
Hair loss
Menstrual irregularities (amenorrhoea /oligomenorrhoea)
Goitre
Heat intolerance
Palpitations/tachycardia/atrial fibrillation
Widened pulse pressure
Nervousness and tremor
Diarrhoea
Hypertension
Agitation and anxiety

For more information

 
References
  1. Guidelines for preventive activities in general practice (The Red Book) 8th Edition. Melbourne: Royal Australian College of General Practitioners, 2012. www.racgp.org.au/your-practice/guidelines/redbook/ (accessed 8 January 2013).
  2. Canaris GJ, Manowitz NR, Mayor G, et al. The Colorado thyroid disease prevalence study. Arch Intern Med 2000;160:526–34. [PubMed]
  3. Gopinath B, Wang JJ, Kifley A, et al. Five-year incidence and progression of thyroid dysfunction in an older population. Intern Med J 2010;40:642–9. [PubMed]
  4. Empson M, Flood V, Ma G, et al. Prevalence of thyroid disease in an older Australian population. Intern Med J 2007;37:448–55. [PubMed]
  5. Helfand M. Screening for subclinical thyroid dysfunction in nonpregnant adults: a summary of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med 2004;140:128–41. [PubMed]
  6. Helfand M, Redfern CC. Clinical guideline, part 2. Screening for thyroid disease: an update. American College of Physicians. Ann Intern Med 1998;129:144–58. [PubMed]
  7. Ochs N, Auer R, Bauer DC, et al. Meta-analysis: subclinical thyroid dysfunction and the risk for coronary heart disease and mortality. Ann Intern Med 2008;148:832–45. [PubMed]
  8. Jaeschke R, Guyatt G, Gerstein H, et al. Does treatment with L-thyroxine influence health status in middle-aged and older adults with subclinical hypothyroidism? J Gen Intern Med 1996;11:744–9. [PubMed]
  9. Parle JV, Franklyn JA, Cross KW, et al. Prevalence and follow-up of abnormal thyrotrophin (TSH) concentrations in the elderly in the United Kingdom. Clin Endocrinol (Oxf) 1991;34:77–83. [PubMed]