Updated July 31, 2015.

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Turkish researchers, reporting in the International Journal of Clinical Practice, looked at Thyroid Stimulating Hormone (TSH) levels and the connection to a number of cardiovascular risk factors, including homocysteine, C-reactive protein (CRP), fibrinogen, D-dimer and serum cholesterol levels. The patients were all taking levothyroxine, the synthetic thyroid medication. More than 400 patients were evaluated, and evaluated as part of three groups.

Group 1 patients had a TSH value of 0.4 to 2.0, and Group 2 were from a TSH of 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. No statistically significant differences were noticed in respect to fibrinogen and d-dimer levels between three groups. There was some correlation between TSH and cholesterol levels.

The key conclusion of the researchers? A target TSH level of less than 2 is advisable to lower CRP levels and homocysteine levels, and possibly lipid parameters.

Targeting a TSH level of 2.0 or less is controversial, however. Currently, the recommended reference range for TSH is from approximately 0.3 to 3.0. A much wider range of approximately 0.5 to from 5.0 to 6.0 is being used by labs and doctors who are not following the latest recommendations by the American Association of Clinical Endocrinologists.

(This controversy is described in detail in my article, The TSH Wars.

Traditionally, practitioners have, for most patients, had their own particular approach to thyroid hormone replacement that fall 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 a patient's 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. This approach itself has been controversial however, because 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 dosage should 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-Normal 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 "normal range" -- and again, most often, using the older, broader normal range of approximately 0.5 to 5.0 to 6.0. 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 more of the 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 experience over time noting at which TSH level 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 with thyroid cancer survivors. Suppression prevents any remnant thyroid tissue from becoming active, and can help prevent cancer recurrence in many patients, and is often recommended by practitioners managing thyroid cancer patients. This approach is considered an important part of the ongoing treatment for thyroid cancer survivors.

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 PATIENTS

With the publication of this new research, there is now 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.