地塞米松抑制试验

定义

The dexamethasone suppression test measures whether cortisol secretion by the adrenal gland can be suppressed. It can also help assess the reason for an excess of cortisol in your body such as if it is due to an excess of adrenocorticotrophic hormone (ACTH) secretion by the pituitary.

选择的名字

DST; ACTH suppression test; Cortisol suppression test

如何执行测试

在此测试中，您将使用地塞米松. This is a strong man-made (synthetic) glucocorticoid medicine. Afterward, your blood is drawn so that the cortisol level in your blood can be measured.

There are two different types of dexamethasone suppression tests: low dose and high dose. Each type can either be done in an overnight (common) or standard (3-day) method (rare). There are different processes that may be used for either test. 下面描述了这些示例.

常见的:

• Low-dose overnight -- You will get 1 milligram (mg) of dexamethasone at 11 p.m., and a health care provider will draw your blood the next morning at 8 a.m. 对于皮质醇测量.
• High-dose overnight -- The provider will measure your cortisol on the morning of the test. 然后在晚上11点给你注射8毫克地塞米松.m. 第二天早上8点抽血.m. 对于皮质醇测量.

罕见:

• Standard low-dose -- Urine is collected over 3 days (stored in 24-hour collection containers) to measure cortisol. 在第2天，您将获得低剂量(0.5 mg) of dexamethasone by mouth every 6 hours for 48 hours.
• Standard high-dose -- Urine is collected over 3 days (stored in 24-hour collection containers) for measurement of cortisol. On day 2, you will receive a high dose (2 mg) of dexamethasone by mouth every 6 hours for 48 hours.

仔细阅读并遵循说明. The most common cause of an abnormal test result is when instructions are not followed.

如何准备考试

Your provider may tell you to stop taking certain medicines that can affect the test, including:

• 抗生素
• 抗癫痫药物
• Medicines that contain corticosteroids, such as hydrocortisone, prednisone
• 雌激素
• 口服避孕(避孕药)
• 水丸(利尿剂)

考试的感觉如何

When the needle is inserted to draw blood, some people feel moderate pain. 其他人只感到刺痛或刺痛. Afterward, there may be some throbbing or slight bruising. 这很快就会消失.

为什么要进行测试

This test is done when your provider suspects that your body is producing too much cortisol. 这样做是为了帮助诊断 库欣综合症 找出原因.

The low-dose test can help tell whether your body is producing too much ACTH. The high-dose test can help determine whether the problem is in the pituitary gland (库欣病)或来自身体的不同部位(异位).

Dexamethasone is a man-made (synthetic) steroid that binds to the same receptor as cortisol. 地塞米松可减少正常人ACTH的释放. Therefore, taking dexamethasone should reduce ACTH level and lead to a decreased cortisol level.

如果你的脑垂体分泌过多的ACTH, 你会对低剂量试验产生异常反应. 但你可以对高剂量试验有正常反应.

正常的结果

Cortisol level should decrease after you receive dexamethasone.

低剂量:

• 过夜——8小时.m. 血浆皮质醇低于1.8 micrograms per deciliter (mcg/dL) or 50 nanomoles per liter (nmol/L)
• Standard -- Urinary free cortisol on day 3 lower than 10 micrograms per day (mcg/day) or 280 nmol/L

高剂量:

• Overnight -- greater than 50% reduction in plasma cortisol
• Standard -- greater than 90% reduction in urinary free cortisol

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different specimens. Talk to your health care provider about the meaning of your specific test results.

异常结果意味着什么

An abnormal response to the low-dose test may mean that you have abnormal release of cortisol (库欣综合症). 这可能是由于:

• 肾上腺肿瘤 产生皮质醇
• 垂体瘤 产生ACTH
• 体内产生ACTH的肿瘤(异位库欣综合征)

The high-dose test can help tell a pituitary cause (库欣病) from other causes. An ACTH blood test may also help identify the cause of high cortisol.

Abnormal results vary based on the condition causing the problem.

由肾上腺肿瘤引起的库欣综合征:

• 低剂量试验，血液皮质醇没有下降
• ACTH水平——低
• 在大多数情况下，不需要进行高剂量试验

异位库欣综合征:

• 低剂量试验，血液皮质醇没有下降
• ACTH水平——高
• 大剂量试验，血液皮质醇没有下降

库欣综合症 caused by a pituitary tumor (库欣病)

• 低剂量试验，血液皮质醇没有下降
• 高剂量试验，预期血液皮质醇降低

由于许多原因，可能会出现错误的测试结果, 包括不同的药物, 肥胖, 抑郁症, 和压力. 错误的结果在女性中比在男性中更常见.

最常, the dexamethasone level in the blood is measured in the morning along with the cortisol level. 为了使测试结果被认为是准确的, the dexamethasone level should be higher than 200 nanograms per deciliter (ng/dL) or 4.5纳摩尔每升(nmol/L). Dexamethasone levels that are lower can cause a false-positive test result.

风险

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another, 从身体的一边到另一边. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

• 大出血
• 昏厥或感到头晕
• 多次穿刺定位静脉
• 血肿(皮肤下积血)
• 感染(任何时候皮肤破裂都有轻微风险)

参考文献

伯瑟夫RL，库珀M，温特WE. 肾上腺皮质. In: Rifai N, Chiu RWK, Young I, Burnham CD, Wittwer CT, eds. Tietz检验医学教科书. 7日艾德. Philadelphia, PA: Elsevier; 2023:chap 56.

Guber HA, Oprea M, Russell YX. 内分泌功能评价. 见:McPherson RA, Pincus MR，编辑. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24日艾德. St Louis, MO: Elsevier; 2022:chap 25.

newwell - price JDC, Auchus RJ. 肾上腺皮质. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. 威廉斯内分泌学教科书. 14日艾德. Philadelphia, PA: Elsevier; 2020:chap 15.