What Is the Optimal TSH Level for Thyroid Patients?

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As a thyroid patient, you quickly learn that your thyroid stimulating hormone (TSH) level is, for conventional practitioners, the most important measurement of your thyroid function, and relied on for your diagnosis and treatment management. 

Surprisingly, however, there is quite a bit of disagreement among experts regarding what specific test result within the TSH reference range is best for you and your thyroid health.

The TSH reference range typically runs from around 0.4 to 4.5, and some practitioners consider the only goal to be getting you into any part of that reference range. Other experts believe that there is a target, what they refer to as the "optimal TSH level," where you may have the best relief from symptoms, as well as reduced risk of other health issues and complications. 

Researchers have evaluated the connections between TSH levels and a number of cardiovascular risk factors, including homocysteine, c-reactive protein (CRP), fibrinogen, and serum cholesterol levels, discovering that as TSH level elevates, so do homocysteine and CRP levels. Elevated homocysteine is a risk factor for heart disease, and elevated CRP is additionally a marker for inflammation. Other studies have shown a connection between elevated TSH levels within the reference range, and an increased risk of type 2 diabetes, recurrent miscarriage, and other health challenges.

A Target TSH Level of 2.0 or Less?

Several studies have concluded that a target TSH level of less than 2 is advisable to lower CRP levels and homocysteine levels, reduce the risk of miscarriage, and minimize other health concerns.

Targeting a TSH level of 2.0 or less is controversial, however. Currently, the recommended reference range for TSH is from approximately 0.4 to 4.5.

 The controversy over the reference range is described in detail in the article about the "TSH Reference Range Wars."

Approaches to Thyroid Hormone Replacement

Traditionally, practitioners have their own particular approach to thyroid hormone replacement, falling into 5 categories:

1. Minimum Medication / High-Normal TSH

Some practitioners have preferred to take the most conservative approach, providing the lowest possible dose of thyroid medication, and targeting the top end of the normal range for your TSH level. Their justification has been a concern over the effects of a lower TSH on bone density, as well as concerns that medication might have negative effects on your heart.

There is contradictory evidence as to whether patients medicated to the lower normal range face an increased risk of osteoporosis. It's also been shown that thyroid medication is safe for most patients, and necessary for heart health. Experts recommend that your dosage increase slowly. If you are a senior or have a history of preexisting heart disease, you should be monitored carefully for any potential cardiac implications.

2. Medication to Mid-Point of the Reference Range

Many practitioners have as their objective to provide enough thyroid hormone replacement for your TSH level to end up somewhere in the middle of the "reference range"—and again, most often, using the range of approximately 0.4 to 4.5.

This is considered a safe strategy for your physician, as conventional medicine says that hypothyroidism is fully treated when you are euthyroid (have a normal TSH level).

3. Medication to the 1.0 to 2.0 Range

Some practitioners—including many integrative and holistic practitioners—have focused on maintaining patients at an optimal TSH level between 1.0 and 2.0 as the target. This target has typically been based not on definitive research, but more on clinical and anecdotal experience over time, noting the TSH level where the majority of their patients typically report feeling their best.

4. Suppression of TSH to 0.0 or Nearly Undetectable Levels

TSH suppression, where higher doses of medication are given to suppress the thyroid's ability to produce any, or most, thyroid hormone is a strategy used mainly with thyroid cancer survivors.

Suppression prevents any remnant thyroid tissue from becoming active, thereby helping prevent thyroid cancer recurrence in many patients, so it is often part of the treatment strategy for thyroid cancer patients.

5. Medication to Eliminate Symptoms

Some practitioners—mainly from the holistic, alternative or integrative community—believe that your TSH levels are largely irrelevant in managing your thyroid. They may occasionally test your TSH, but their target is resolution of your thyroid symptoms, and they will change the dosage of thyroid hormone medication based on your self-reported symptoms, as well as your clinical signs including pulse rate, blood pressure, and observable thyroid symptoms such as reflexes, goiter size, eye irritation, and swelling in your face and extremities.

A Word From Verywell

There is scientific justification for doctors to avoid giving only enough medication for you to reach high-normal or mid-range TSH levels. A growing body of evidence suggests that a target level of 2.0 or less may be optimal, and safely resolve your symptoms.

If your doctor is maintaining your TSH level higher than 2.0, consider having a conversation to discuss whether this is in your best interest health-wise, and whether you might benefit from an increase in the dosage of your thyroid hormone replacement medication.

Sources:

Braverman, L, Cooper D. Werner & Ingbar's The Thyroid, 10th Edition. WLL/Wolters Kluwer; 2012.

Decandia F. "Risk factors for cardiovascular disease in subclinical hypothyroidism." Ir J Med Sci. 2017 May 10. 

Gursoy A, et. al. "Which thyroid-stimulating hormone level should be sought in hypothyroid patients under L-thyroxine replacement therapy?Int J Clin Pract. 2006 Jun;60(6):655-9.

Jonklaas, J et al. "Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement (2014)." Thyroid 24(12): 1670-1751, 2014.

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