Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (842 page)

   High urinary copper levels support the diagnosis but are not unique to Wilson disease, as they can be sometimes observed in autoimmune hepatitis and cholestasis.

CORTICOTROPIN-RELEASING HORMONE (CRH)

   Definition

   CRH is a 41-amino-acid peptide hypothalamic factor that increases ACTH release from pituitary cells. CRH is synthesized by neurons in the parvocellular division of the hypothalamic paraventricular nuclei. The axons of the nuclei project to the median eminence, where CRH is secreted into the hypophyseal portal blood. The ACTH released by CRH stimulates the secretion of cortisol and other adrenal steroids, such as DHEA and, transiently, aldosterone. CRH circulates in human plasma bound to a high-affinity binding protein, which reduces its bioactivity and increases its clearance. In addition to being produced in the hypothalamus, CRH is also synthesized in peripheral tissues, such as T lymphocytes, and is highly expressed in the placenta. In the placenta, CRH is a marker that determines the length of gestation and the timing of parturition and delivery. Other names: corticoliberin, corticotropin-releasing factor (CRF).

   
Normal range:
up to 10 pg/mL.

   Use

   To exclude the possibility of an extrapituitary CRH-secreting tumor

   Interpretation

Increased In

   Cushing syndrome

   Ectopic tumors producing ACTH

   Third trimester of pregnancy

Decreased In

   Alzheimer disease

   Autosomal recessive hypothalamic corticotropin deficiency

   Limitations