Thyroid Function Test: When to Get Checked and How Often

Is thyroid screening recommended for everyone?

Major guidelines do not recommend routine thyroid screening for all asymptomatic adults with no risk factors. The U.S. Preventive Services Task Force, the American Thyroid Association, and other professional bodies have reviewed the evidence and concluded that universal screening of the general population does not clearly improve health outcomes over targeted testing in people with symptoms or elevated risk.

This is different from targeted case-finding — testing people who have symptoms or specific risk factors — which is widely supported and appropriate 1Ref 1Jonklaas J, Bianco AC, Bauer AJ, et al. (2014).Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement.Targeted case-finding approach rather than universal screening; risk factors for thyroid disease; TSH as first-line test; older women as higher-risk group.

Who should be tested for thyroid disease?

Testing is appropriate when any of the following apply:

Symptoms that might indicate thyroid dysfunction: - Unexplained fatigue or low energy - Weight gain or weight loss without a change in diet or activity - Cold or heat intolerance - Dry skin, hair thinning, or hair loss - Constipation or frequent loose stools - Rapid or irregular heartbeat - Depression, anxiety, or mood changes - Cognitive changes, brain fog, or difficulty concentrating - Menstrual irregularities

Risk factors that warrant testing even without clear symptoms: - Family history of thyroid disease (hypothyroidism, hyperthyroidism, Hashimoto's, or Graves' disease) - Personal history of an autoimmune condition (type 1 diabetes, rheumatoid arthritis, lupus, vitiligo, celiac disease, Addison's disease) - Prior thyroid disease, thyroid surgery, or radioactive iodine treatment - History of neck radiation - Pregnancy or planning to conceive (see below) - Certain medications: amiodarone, lithium, interferon, checkpoint inhibitors, and others can affect thyroid function - Goiter (enlarged thyroid gland) on examination

Age: Some guidelines suggest that older adults — particularly women over 60 — are at increased risk and may benefit from periodic testing, though this is a clinical judgment rather than a universal protocol 1Ref 1Jonklaas J, Bianco AC, Bauer AJ, et al. (2014).Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement.Targeted case-finding approach rather than universal screening; risk factors for thyroid disease; TSH as first-line test; older women as higher-risk group2Ref 2Ross DS, Burch HB, Cooper DS, Greenlee MC, Laurberg P, Maia AL, Rivkees SA, Samuels M, Sosa JA, Stan MN, Walter MA (2016).2016 American Thyroid Association Guidelines for Diagnosis and Management of Hyperthyroidism and Other Causes of Thyrotoxicosis.Medications that affect thyroid function; pregnancy-related monitoring for known thyroid disease and antibody-positive women.

How often should thyroid levels be monitored during pregnancy?

Women who are pregnant or trying to conceive deserve particular attention. Thyroid hormone demand increases during pregnancy, and untreated hypothyroidism carries risks for the pregnancy and for fetal neurodevelopment. Women with known thyroid disease on levothyroxine typically have their TSH checked every four weeks during the first half of pregnancy and every four to six weeks thereafter. Women with thyroid antibodies but currently normal thyroid function should also be monitored, as thyroid status can change during pregnancy 2Ref 2Ross DS, Burch HB, Cooper DS, Greenlee MC, Laurberg P, Maia AL, Rivkees SA, Samuels M, Sosa JA, Stan MN, Walter MA (2016).2016 American Thyroid Association Guidelines for Diagnosis and Management of Hyperthyroidism and Other Causes of Thyrotoxicosis.Medications that affect thyroid function; pregnancy-related monitoring for known thyroid disease and antibody-positive women.

How often should thyroid function be rechecked once diagnosed?

If you are already being treated for thyroid disease:

• After starting or changing a levothyroxine dose: Recheck TSH in four to six weeks, as it takes that long for TSH to stabilize after a dose change.
• Stable hypothyroidism on levothyroxine: Annual TSH is generally adequate once levels are stable and symptoms are controlled.
• Known autoimmune thyroid disease (Hashimoto's) with currently normal thyroid function: Annual or every-other-year TSH monitoring is often recommended, since thyroid function can change over time.
• Following treatment for thyroid cancer: More frequent monitoring of TSH, thyroglobulin, and neck ultrasound is required — the schedule is determined by the treating endocrinologist based on recurrence risk 3Ref 3Haugen BR, Alexander EK, Bible KC, Doherty GM, Mandel SJ, Nikiforov YE, Pacini F, Randolph GW, Sawka AM, Schlumberger M, Schuff KG, Sherman SI, Sosa JA, Steward DL, Tuttle RM, Wartofsky L (2016).2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer.Follow-up monitoring frequency after thyroid cancer treatment.
• Hyperthyroidism under treatment: More frequent checks during the treatment phase until thyroid levels stabilize.

If you feel well, your results are stable, and you have no symptoms, annual testing is often sufficient for most thyroid conditions.

What is the first thyroid test ordered?

TSH (thyroid-stimulating hormone) is the standard first-line screening test. It is the most sensitive indicator of thyroid dysfunction. If TSH is abnormal, free T4 is typically added. Thyroid antibodies (anti-TPO) may be ordered when autoimmune thyroid disease is suspected, or when TSH is borderline elevated and the clinical picture is ambiguous 1Ref 1Jonklaas J, Bianco AC, Bauer AJ, et al. (2014).Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement.Targeted case-finding approach rather than universal screening; risk factors for thyroid disease; TSH as first-line test; older women as higher-risk group.

How Gale can help

A Gale primary care clinician can review your history, symptoms, and risk factors and help you decide whether thyroid testing is appropriate. If you already have thyroid test results, Gale can help you understand what they mean and whether follow-up is needed. For complex thyroid conditions, coordination with an endocrinologist is part of the care team approach.