Guest Author - Jim Lowrance

The TSH blood lab test, which is used to monitor thyroid function, can detect thyroid hormone imbalances sooner than any other test of thyroid function. It is not a thyroid hormone, but rather one that comes from the pituitary gland, and can determine whether a person's thyroid is functioning properly.

TSH stands for “Thyroid Stimulating Hormone”. It is the hormone sent from the pituitary gland, which is found within the brain and considered to be a master gland that helps regulate hormones in the body. In the case of TSH, the pituitary sends this hormone in varied amounts throughout the day to regulate the amount of thyroid hormones that are released from the thyroid gland.

The pituitary gland sends more TSH when the thyroid gland is under-active and less TSH when it is overactive. At times the thyroid gland needs more stimulation because it is under-functioning. When hypothyroidism develops, more TSH will be released from the pituitary gland, which sends a signal to the thyroid to put out more of its own hormones. The two major thyroid hormones are the “T-3 and T-4” hormones. If the pituitary senses that the thyroid is producing and sending out too much thyroid hormone into the body, it will then send less TSH to the thyroid. Less TSH is sent so that the thyroid is not being overly stimulated to continue providing the body with too much thyroid hormone, which is referred to as hyperthyroidism.

TSH is the most commonly used test to evaluate thyroid function. Since the discovery of the TSH blood test several decades ago and how it can determine thyroid function, it has become the single most commonly tested hormone level to monitor thyroid function. Not only is it used to detect an overactive or under-active thyroid gland, but it is also used to monitor patients who are being treated for either of these thyroid disorders to insure their treatments are getting proper results in correcting these two types of thyroid hormone imbalances. Doctors will use TSH because it will detect the onset of thyroid hormone imbalance sooner than any of the other thyroid function tests.

The normal range for TSH testing was revised. In 2002, The American Association of Clinical Endocrinologists revised the normal range to diagnose earlier cases of developing thyroid disorders. This revision was due to the fact that these experts in the field of endocrine medicine (the thyroid is an endocrine gland) believed that the previous TSH normal value was too wide and would potentially miss many developing cases of thyroid hormone imbalance disorders. The previous TSH range that blood testing labs were using was roughly “0.5 to 5.0” and the AACE recommended that the TSH normal values range be narrowed to “0.3 to 3.04”. This in their view will help to diagnose many more millions of patients with developing thyroid hormone imbalances, so that they will be recommended for follow-up testing or begin treatment.

TSH blood testing is recommended for adults beginning at age 35 or at any age that thyroid disease symptoms may develop. Statistics have revealed that thyroid diseases manifest more commonly in people who are between ages 35 and 40 and are at least five times more common in women than in men. Adults approaching their middle age years should have their TSH level tested as a precaution to detect possible developing thyroid disease. And this is also more important for women, who more commonly develop thyroid hormone imbalances. Younger women should also be tested during pregnancy, which can also increase the risk for thyroid hormone imbalances.

TSH is the single most valuable tool available to doctors who can order the blood test for their patients who fit into the risk categories described above.