The CRH stimulation test is a medical diagnostic procedure used to evaluate the functioning of the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis is a complex regulatory system in the body responsible for controlling the release of cortisol, a hormone that plays a crucial role in the body's stress response and various other physiological processes. The test involves the administration of a synthetic hormone called corticotropin-releasing hormone (CRH) to stimulate the release of adrenocorticotropic hormone (ACTH) from the pituitary gland. ACTH, in turn, stimulates the adrenal glands to produce cortisol. By measuring the levels of cortisol before and after the administration of CRH, doctors can gain insights into the health and functionality of the HPA axis. The CRH stimulation test is primarily used in the diagnosis and differentiation of certain endocrine disorders, including: 1. Adrenal Insufficiency: Also known as Addison's disease, adrenal insufficiency is characterized by the inadequate production of cortisol and sometimes aldosterone by the adrenal glands. The CRH stimulation test can help differentiate primary adrenal insufficiency (failure of the adrenal glands themselves) from secondary adrenal insufficiency (failure of the pituitary or hypothalamus to produce appropriate amounts of ACTH). 2. Cushing's Syndrome: Cushing's syndrome is a condition in which the body is exposed to excessive levels of cortisol. The CRH stimulation test can help determine the source of the excess cortisol production, whether it's due to an issue with the adrenal glands, the pituitary gland, or an ectopic source (a non-pituitary tumor producing ACTH). The procedure for the CRH stimulation test generally involves the following steps: 1. Baseline Blood Sample: A blood sample is taken before the administration of CRH to measure the baseline levels of cortisol and possibly other related hormones. 2. CRH Administration: A synthetic form of CRH is injected into the patient's bloodstream. This prompts the pituitary gland to release ACTH. 3. Follow-Up Blood Samples: Blood samples are taken at specific intervals (often at 15, 30, 45, and 60 minutes after CRH injection) to monitor the rise in cortisol levels in response to the stimulation. 4. Interpretation: The cortisol levels in the blood samples are analyzed, and the results are compared to reference ranges. An appropriate rise in cortisol levels indicates a normal HPA axis response, while a blunted or inadequate response could suggest a dysfunction in the HPA axis. It's important to note that the CRH stimulation test should be conducted under the supervision of a healthcare professional, as the test involves the administration of a hormone and the monitoring of cortisol levels, which can have potential risks and complications if not managed properly. The test is generally considered safe, but individual patient factors and medical history should be taken into consideration. As with any medical test, the interpretation of results should be done by a qualified healthcare provider in the context of the patient's overall clinical picture.

• published: 10 Jan 2021
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