Whether testing for TSH is a good idea was addressed by the USPSTF, the United States Preventive Services Task Force, a group of individuals that studies whether there is compelling evidence to perform particular tests and other clinical assessments. Their efforts are considered to be highly professional and to offer a rational approach to the practice of Medicine in our complex modern environment.
The USPSTF has concluded that there is insufficient evidence (category I) to recommend thyroid testing in asymptomatic individuals.
Their recommendations are provided below verbatim:
Screening for Thyroid Dysfunction: Clinical Summary of USPSTF Recommendation.
Population: Nonpregnant, asymptomatic adults
Recommendation: No recommendation.
Grade: I statement (insufficient evidence)
Risk factors for an elevated thyroid-stimulating hormone (TSH) level include female sex, advancing age, white race, type 1 diabetes, Down syndrome, family history of thyroid disease, goiter, previous hyperthyroidism, and external-beam radiation in the head and neck area. Risk factors for a low TSH level include female sex; advancing age; black race; low iodine intake; personal or family history of thyroid disease; and ingestion of iodine-containing drugs, such as amiodarone.
The primary screening test for thyroid dysfunction is serum TSH testing. Multiple tests over 3 to 6 mo should be performed to confirm or rule out abnormal findings. Follow-up testing of serum thyroxine (T4) levels in persons with persistently abnormal TSH levels can differentiate between subclinical (normal T4) and “overt” (abnormal T4) thyroid dysfunction.
Treatment and Interventions
Hypothyroidism is treated with oral T4 monotherapy (levothyroxine sodium). Consensus is lacking on the appropriate point for clinical intervention, especially for TSH levels <10.0 mIU/L. Hyperthyroidism is treated with antithyroid medications (e.g., methimazole) or nonreversible thyroid ablation therapy (e.g., radioactive iodine or surgery). Treatment is generally recommended for patients with a TSH level that is undetectable or <0.1 mIU/L, particularly those with overt Graves disease or nodular thyroid disease.
Balance of Benefits and Harms
The current evidence is insufficient to assess the balance of benefits and harms of screening for thyroid dysfunction in nonpregnant asymptomatic adults.
Reference: M. L. LeFevre, on behalf of the U.S. Preventive Services Task Force, Screening for Thyroid Dysfunction: U.S. Preventive Services Task Force Recommendation Statement. Ann Intern Med. 2015;162:641-650. doi:10.7326/M15-0483 .
Note that this is not just a recommendation, or lack thereof, about whether to test for thyroid abnormalities in asymptomatic (non-pregnant) adults, it also gives an important clue as to whether individuals with TSH values of <10.0 mIU/L should be treated at all when the recommendation states: “Hypothyroidism is treated with oral T4 monotherapy (levothyroxine sodium). Consensus is lacking on the appropriate point for clinical intervention, especially for TSH levels <10.0 mIU/L.”
So why is there no consensus on when to treat patients with thyroid dysfunction? Because your TSH values are highly variable and change during the day and are subject to change throughout your life. I have already mentioned the previous posts illustrating issues with when TSH blood levels are drawn and the effects of ageing. Let me quote directly from the article already cited above:
“False-positive results on serum TSH tests are common due to several factors. Secretion of TSH is sensitive to multiple factors unrelated to thyroid conditions; varies across time intervals, sometimes as short as a day; and varies depending on the population being considered (average TSH values may differ by age, sex, and race/ethnicity). In addition, there is no universally agreed-on “normal” TSH reference value, in part because it is not linked to the risk for actual adverse health outcomes.
"Reliable estimates of the frequency of false-positive results from serum TSH tests are not available. A prospective observational study followed a cohort of 599 older adults after a single baseline TSH test, with repeated testing of 376 participants at the end of the study. It found that 37% (11 of 30) of participants with an initially elevated TSH level and 29% (5 of 17) with an initially low TSH level reverted to normal thyroid function after 3 years without intervention.”
You can learn more about issues with TSH testing by reading my eBook “Blood Trails: Follow your medical lab work from beginning to end with everything that can go wrong in between, plus how doctors misunderstand and misuse blood tests,” available at amazon .com (https://www.amazon.com/Blood-Trails-beginning-everything-misunderstand-ebook/dp/B00YZ1XADE/ref=sr_1_1?ie=UTF8&qid=1471897020&sr=8-1&keywords=ralph+giorno#nav-subnav).
If you are asymptomatic, you should not be screened for thyroid issues (dysfunction). This will be a problem for many practitioners and “health and wellness” fairs, because they are big proponents of thyroid testing. That is because they have a big financial stake in testing and subsequent treatment.
What are the symptoms of hypothyroidism (decreased thyroid function)? Briefly, fatigue, lethargy, hair loss, dry hair and skin, cold sensitivity, weight gain.
What are the symptoms of hyperthyroidism (increased thyroid function)? Again, briefly, restlessness, nervousness, hyperactivity, irritability, insomnia, rapid pulse, weight loss.
If you do not have at least a couple of these things going on, there is no point in having your thyroid tested by means of the TSH test.
© 2016 by Ralph Giorno MD