Recommendation on screening adults for asymptomatic thyroid dysfunction in primary care

Abstract

his guideline from the Canadian Task Force on Preventive Health Care focuses on screening for thyroid dysfunction among asymptomatic nonpregnant adults in primary care beyond usual care and vigilance for signs and symptoms of thyroid dysfunction. Thyroid dysfunction is diagnosed based on abnormal levels of serum thyroid-stimulating hormone (TSH) and can be characterized as either hypo-or hyperthyroidism. Hypothyroidism results from impaired thyroid hormone production (i.e., thyroxine [T 4 ] or triiodothyronine [T 3 ]), leading to elevated levels of TSH. Hypothyroidism is often caused by autoimmune disorders (e.g., Hashimoto thyroiditis) or occurs as a sequela of hyperthyroidism treatment, which can render the thyroid gland nonfunctional. 1 Hyperthyroidism results from an overproduction of thyroid hormone, leading to the suppression of TSH. 1 Causes of hyperthyroidism include Graves disease, toxic multinodular goitre and toxic adenoma. ] Some people with thyroid dysfunction are asymptomatic. f left untreated, hypothyroidism may increase the risk of cardiac dysfunction, hypertension, dyslipidemia, cognitive impairment and, in rare cases, myxedema coma. Untreated hyperthyroidism may increase the risk of cardiac conditions (e.g., atrial fibrillation, heart failure) or bone fractures, and could lead to thyroid storm, an uncommon, life-threatening condition associated with tachycardia, extreme fatigue, fever and nausea. nor variations in thyroid function as measured by abnormal levels of TSH are often self-limiting. Observational studies have reported that levels of TSH appear to revert to normal without treatment in 37%-62% of patients with initially elevated levels and 51% with initially low levels, particularly for milder cases of thyroid dysfunction (mean follow-up 32-60 mo). creening is intended to detect thyroid dysfunction in asymptomatic patients in order to prevent adverse consequences of untreated thyroid dysfunction. Screening is done by performing a blood test for TSH. Abnormal levels of TSH are followed up with additional diagnostic testing that often includes blood tests to measure thyroid hormone levels or other tests (e.g., ultrasound) as warranted. An estimated 10% of Canadians aged 45 years or older report that they have been diagnosed with thyroid dysfunction, and prevalence is higher in women (16%) than in men (4%). Prevalence has also been reported to be higher in adults older than 85 years (16%),