What is the Optimal TSH Level for Thyroid Patients?

target tsh level for thyroid patients
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Thyroid patients quickly learn that the thyroid stimulating hormone (TSH) level is, for conventional practitioners, the most important measurement of thyroid function for 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 thyroid patients. 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.

Others feel that there is a narrower, "optimal" range for TSH where you may have the best relief from symptoms, as well as reduced risk of other health issues and complications. 

Turkish researchers reported in the International Journal of Clinical Practice on one important study that looked at TSH levels and the connection to a number of cardiovascular risk factors, including homocysteine, c-reactive protein (CRP), fibrinogen, and serum cholesterol levels. The patients were all taking levothyroxine, the synthetic thyroid medication. In the study, patients were evaluated as part of three groups. Group 1 patients had a TSH value of 0.4 to 2.0, Group 2 had TSH levels from 2.0 to less than 5.5, and Group 3 were from 5.5 to less than 20.

The researchers found that as TSH level elevated, so did homocysteine and CRP levels, with the highest levels seen in Group 3 patients. Elevated homocysteine is a risk factor for heart disease, and elevated CRP is additionally a marker for inflammation.

There was some correlation between TSH and cholesterol levels.

A Target TSH Level of 2.0 or Less?

The researchers came to a key conclusion and recommendation: A target TSH level of less than 2 is advisable to lower CRP levels and homocysteine levels.

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 Wars.

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 the 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 the dosage be increased slowly and monitored carefully for cardiac implications in only the elderly and people with a history of preexisting heart conditions.

2. Medication to Mid-Point of the Reference Range

Many practitioners have as their objective to provide enough thyroid hormone replacement for a patient's 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 the physician, as conventional medicine says that hypothyroidism is fully "treated" when the patient is euthyroid (has 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 a TSH level of between 1.0 and 2.0 as the target range. 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 the TSH levels are irrelevant in managing a patient. They may occasionally test the TSH, but their target is resolution of thyroid symptoms, and they will change the dosage of thyroid hormone medication based on a patient's self-reported symptoms, as well as clinical signs including pulse rate, blood pressure, and observable thyroid symptoms such as reflexes, goiter size, eye irritation, and swelling in the face and extremities.

Implications for You 

With the publication of this research, there is scientific justification for doctors to avoid undermedicating patients to high-normal or mid-range TSH levels, and instead, target a level of 2.0 or less, in order to ensure that their patients are receiving optimal care. If your doctor is maintaining your TSH level higher than 2.0, it's time to have a conversation to discuss whether this is in your best interest. 

Source:

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

Garber, J, Cobin, R, Gharib, H, et. al. "Clinical Practice Guidelines for Hypothyroidism in Adults: Cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association." Endocrine Practice. Vol 18 No. 6 November/December 2012.

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​

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