出典:Wikipedia
出典:『Wikipedia』 (2011/04/01 18:43 UTC 版)
A TRH test may be indicated if secondary hypothyroidism is suspected. Some patients may have low levels of circulating thyroid hormones and secondary hypothyroidism as a result of damage to the hypothalamic or pituitary control mechanisms that regulate thyroid function. The hypothalamus secretes the thyrotropin-releasing hormone that directs the synthesis and secretion of TSH from the pituitary gland. If these normal regulatory mechanisms are interrupted, the pituitary may not be able to produce appropriate levels of TSH and levels of thyroid hormones may decline, although the TSH remains appropriately normal.