What is the significance of elevated Thyroid-Stimulating Hormone (TSH) levels, specifically 8.6, in a patient taking levothyroxine (Synthroid) 150 micrograms (mcg)?

From the Guidelines

Your elevated TSH level of 8.6 while taking levothyroxine 150mcg indicates your thyroid medication dose needs adjustment. You should contact your healthcare provider to increase your levothyroxine dose, as your current dose isn't adequately controlling your hypothyroidism. Do not adjust the dose yourself. Continue taking your current dose until your provider recommends changes. Your provider will likely increase your dose by 12.5-25mcg and recheck your thyroid levels in 6-8 weeks. This elevated TSH suggests your body is still trying to stimulate your thyroid to produce more hormone, despite the supplementation you're receiving. Several factors can affect levothyroxine absorption, including taking it with food, calcium supplements, iron supplements, or certain medications. For optimal absorption, take levothyroxine on an empty stomach with water, at least 30-60 minutes before eating or taking other medications. Consistency in timing is important for stable thyroid levels. Some patients require higher doses due to weight, metabolism differences, or malabsorption issues 1.

Key Considerations

• The USPSTF found no direct evidence on the benefits and harms of screening for thyroid dysfunction in nonpregnant, asymptomatic adults 1.
• Levothyroxine therapy is a synthetic preparation of a natural hormone found in the body, and treatment of hypothyroidism with levothyroxine generally lasts for many years 1.
• The previous review found that one quarter of patients who received levothyroxine were inadvertently maintained on doses high enough to make TSH levels undetectable 1.
• Five trials published since the previous review assessed the harms of treatment of hypothyroidism with levothyroxine and generally reported no indication of harms or no or minimal withdrawals from treatment due to adverse effects 1.
• The optimal screening interval for thyroid dysfunction is unknown 1.
• The principal treatment for hypothyroidism is oral T4 monotherapy (levothyroxine sodium) 1.
• Patients who are overdiagnosed and overtreated could develop iatrogenic hypothyroidism and become dependent on lifelong thyroid hormone therapy 1.

Recommendations

• Contact your healthcare provider to increase your levothyroxine dose.
• Do not adjust the dose yourself.
• Continue taking your current dose until your provider recommends changes.
• Take levothyroxine on an empty stomach with water, at least 30-60 minutes before eating or taking other medications.
• Consistency in timing is important for stable thyroid levels.

From the FDA Drug Label

In adult patients with primary hypothyroidism, monitor serum TSH levels after an interval of 6 to 8 weeks after any change in dosage. The general aim of therapy is to normalize the serum TSH level Failure of the serum T4 to increase into the upper half of the normal range within 2 weeks of initiation of levothyroxine sodium therapy and/or of the serum TSH to decrease below 20 IU per litre within 4 weeks may indicate the patient is not receiving adequate therapy

The patient's TSH level is elevated at 8.6 while taking levothyroxine 150mcg. Key points:

• The goal of therapy is to normalize the serum TSH level.
• The patient's current TSH level is above normal, indicating that the current dosage may not be adequate.
• The FDA label recommends monitoring TSH levels after 6-8 weeks of any dosage change and adjusting the dosage as needed to achieve a normal TSH level. Based on this information, the patient's levothyroxine dosage may need to be adjusted to achieve a normal TSH level 2.

From the Research

TSH Levels and Levothyroxine Treatment

• A TSH level of 8.6 is considered elevated, and the patient is currently taking levothyroxine 150mcg 3.
• The treatment guidelines for hypothyroidism recommend levothyroxine therapy, but the decision to start treatment should be based on clinical and laboratory findings, not just a simple TSH elevation 3.
• The risk of progression to overt hypothyroidism is about 3% to 4% per year overall, but increases with the initial TSH level 3.

Monitoring and Adjusting Levothyroxine Dose

• Treatment monitoring is based mainly on blood TSH assay, and dose adjustment should only be considered after 6 to 12 weeks, given the long half-life of levothyroxine 3.
• Certain drugs, such as iron and calcium, reduce the gastrointestinal absorption of levothyroxine, and enzyme inducers reduce its efficacy 3.
• A study found that females with TSH above 6.9 mIU/L, particularly those with free triiodothyronine (FT3) and FT4 in the lower half of the reference range, are more likely to develop biochemical hypothyroidism 4.

Clinical Practice and Treatment Outcomes

• A retrospective study found that 34.3% of patients with elevated TSH levels received repeat TSH testing, and 12.4% received direct levothyroxine replacement in primary care during follow-up 5.
• The study also found that repeat TSH testing showed the strongest association with overt hypothyroidism, and was more common among patients with high primary care utilization and among patients aged 40-64 years compared to patients aged <40 years 5.
• Another study found that combination therapy with levothyroxine and slow-release T3 (SRT3) in the treatment of hypothyroidism results in a normal triiodothyronine/thyroxine (T3/T4) ratio above that of levothyroxine monotherapy 6, 7.