What Does Low Thyroid Blood Test Mean?

By Mary Shomon – Reviewed by a board-certified doctor.

This is one of those problems about thyroid treatment that tends to confuse individuals. So here’s a basic description.

Your thyroid gland produces thyroid hormone. When it operates correctly, your thyroid is part of a feedback loop with your pituitary gland that involves a number of crucial steps.

1. First, your pituitary senses the level of thyroid hormone that the thyroid has actually released into the blood stream.

2. Your pituitary then launches a special messenger hormone, called “Thyroid Stimulating Hormone” (abbreviated as TSH). The role of TSH is to promote the thyroid to release more thyroid hormone.

When your thyroid, for whatever factor– health problem, stress, surgery, obstruction, for example– doesn’t or cannot produce adequate thyroid hormone, your pituitary spots this reduction in thyroid hormone, and it moves into action by making MORE TSH, which then activates your thyroid to make more thyroid hormone. This is the pituitary’s effort to return the system to “regular” and normalize thyroid function.

thyroid system

Thyroid system

So, a TSH that is greater than typical recommends a thyroid that is underactive and refraining from doing its task of producing enough thyroid hormone. To generalize, then, HIGHER TSH = UNDERACTIVE THYROID/ HYPOTHYROIDISM.

3. If your thyroid is overactive and producing excessive thyroid hormone– due to disease, or taking expensive a dosage of thyroid hormone replacement drugs– your pituitary senses that there is excessive thyroid hormone circulating, and slows or shuts down TSH production, so that the thyroid will decrease its production of the hormone.

This drop in TSH is an effort to return circulating thyroid hormone levels to normal.

So, a test to determine the amount of TSH in your system will generally show lower than normal TSH when the thyroid is overactive.

So, in basic, LOWER TSH = OVERACTIVE THYROID/ HYPERTHYROIDISM.

During diagnosis, the majority of doctors use the TSH test to assess your thyroid function and identify the optimum course of treatment. [KEEP IN MIND: nevertheless, that some specialists feel that relying entirely on TSH– a pituitary hormone– without also assessing the circulating levels of real thyroid hormones T4 and T3– may not have the ability to identify more subtle thyroid problems, or conditions that are resulting from the inappropriate conversion of thyroid hormones. TSH is likewise not always enough to monitor hypothyroidism during pregnancy. For these factors, some professionals also include other important blood tests, including T4, T3, Free T4, Free T3, Reverse T3, and antibodies tests.]

A major drawback in this connection of TSH to hypothyroidism and hyperthyroidism is an ongoing dispute in the medical world over the recommendation range for the TSH test.

Levels listed below 0.5 are considered possible evidence of hyperthyroidism, and levels above 5.0 are usually thought about possible proof of hypothyroidism, but some professionals feel this variety is too broad, and that it ought to be narrowed substantially, to 0.3 to 3.0. This is an issue that is still under argument.

When you are being treated for hypothyroidism with thyroid hormone replacement drugs, doctors will typically attempt to medicate you into this so-called “regular” referral range– of a TSH from.3/.5 on the low-end, to 3.0/ 5.0 on the high-end. (Patients who have had thyroid cancer, nevertheless, are frequently provided suppressive dosages that keep TSH close to 0 in order to prevent cancer recurrence).

So, when you’ve gone for an examination, and your TSH can be found in below regular (and your doctor does not have you on a suppressive dosage of thyroid hormone), they might wish to REDUCE your dose of thyroid hormone, due to the fact that levels below typical are considered possibly “hyperthyroid” (overactive.)

Another point of controversy: Once on medication, some patients might find relief from hypothyroidism symptoms just when the TSH level drops below the normal variety. Because case, some medical professionals will also check Free T4 and Free T3 levels, thinking that it’s acceptable for a patient to have a below-normal TSH, as long as Free T4 and Free T3 levels are normal.

And if your TSH test can be found in above typical, some doctors will wish to INCREASE your dosage of thyroid hormone, since levels above regular are thought about potentially “hypothyroid” (underactive.).

Health Tips

LOW TSH recommends you are closer to HYPERthyroidism (overactive), and have excessive thyroid hormone circulating.

HIGH TSH suggests you are better to HYPOthyroidism (underactive), and you don’t have enough thyroid hormone distributing.

 

Updated: 22.12.2016 — 07:38

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