Member of the 1000 Post Club friday Posted September 4, 2004 Member of the 1000 Post Club Report Share Posted September 4, 2004 From http://thyroid.about.com/od/thyroidbasicst...fusion.htm?nl=1 Why Low TSH means Less Medicine and Other Confusing Thyroid Issues Your Guide, Mary Shomon From Mary Shomon, Your Guide to Thyroid Disease. FREE Newsletter. Sign Up Now! Many people write to me asking me to lease explain to me "why, when my TSH results show that my TSH has dropped, the doctor wants to LOWER instead of RAISE my medicine?" Or, "doesn't a high TSH mean I have too much thyroid? And if that's the case, why is the doctor INCREASING my thyroid hormone medicine?" This is one of those confusing issues that people frequently write to ask about, hoping for an explanation. Let me try to take you through it to clarify. First, the thyroid produces thyroid hormone. When it's functioning properly, the thyroid is part of a feedback loop with the pituitary gland. The pituitary senses the level of thyroid hormone that the thyroid has released into the bloodstream. The pituitary releases "Thyroid Stimulating Hormone" (also known as TSH) to stimulate the thyroid to release more thyroid hormone. Usually, the pituitary is releasing TSH at a steady, normal rate, to maintain a steady normal rate of thyroid hormone in the bloodstream. When the thyroid, for whatever reason -- illness, stress, surgery, obstruction, etc. -- doesn't produce enough thyroid hormone, the pituitary detects this reduction in thyroid hormone, and it moves into action. The pituitary makes MORE TSH, to help trigger the thyroid to produce more thyroid hormone, in an effort to return the system to "normal." So, the test to measure the amount of TSH in your system will show higher than normal TSH levels when the thyroid is underactive, because more TSH is being produced when your thyroid isn't doing its job. So, HIGHER TSH = UNDERACTIVE THYROID / HYPOTHYROIDISM. If the thyroid is overactive and producing too much thyroid hormone -- due to disease, or taking too high a dose of thyroid hormone replacement drugs -- the pituitary senses that there is too much thyroid hormone circulating. The pituitary then slows or shuts down TSH production, so that the thyroid will slow down production of hormone. This drop in TSH is an attempt to to return circulating thyroid hormone levels to normal. So, a test to measure the amount of TSH in your system will show lower than normal TSH when the thyroid is overactive. So, LOWER TSH = OVERACTIVE THYROID / HYPERTHYROIDISM. If you are being diagnosed, the doctor will use the TSH test -- and hopefully, other valuable tests, including T4, T3, Free T4, Free T3, and antibodies tests -- to evaluate your thyroid function and determine the optimal course of treatment. But generally, for those who use TSH as a guideline, a TSH level from 0 to .30 is considered hyperthyroid/overactive, and a TSH over 3.0 is considered hypothyroid, or underactive. When you are being treated for hypothyroidism with thyroid hormone replacement drugs, doctors will typically attempt to medicate you into the so-called "normal" range -- of .3 to 3.0. (Patients who have had thyroid cancer, however, are often given suppressive doses that maintain TSH near to 0 in order to prevent cancer recurrence). So, when you've gone for a checkup, and your TSH comes in below .3 (and your doctor does not have you on a suppressive dose of thyroid hormone), they will often REDUCE your dosage of thyroid hormone, because levels below .3 are considered "hyperthyroid" (overactive.) And if your TSH test comes in above 3.0, doctors will often INCREASE your dosage of thyroid hormone, because levels above 3.0 are considered "hypothyroid" (underactive.) To recap: LOW TSH means closer to HYPERthyroidism (overactive), too much thyroid hormone circulating. HIGH TSH means closer to HYPOthyroidism (underactive), not enough thyroid hormone circulating. If you're being treated with thyroid hormone drugs (such as Synthroid, Levoxyl, Armour, Thyrolar, etc.), if your TSH comes back as too low, most doctors will usually LOWER your dose. When TSH tests come back as higher, that means HYPOthyroidism (underactive), and doctors will typically RAISE your dose It can sound counterintuitive, but that's how it works! Important disclaimer information about this About site. Quote Link to comment Share on other sites More sharing options...
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