A deficiency of the 21-hydroxylase (CYP21) enzyme produces various types of congenital adrenal hyperplasia (CAH). Classical CAH in newborns (also known as salt-losing CAH, SLCAH) manifests as a salt-losing syndrome due to severe cortisol and aldosterone deficiency, whereas simple virilizing CAH (SVCAH) is less severe and manifests without salt loss as a cortisol deficiency. The late-onset form of CAH (LOCAH, also known as non-classical CAH) manifests in pubertal girls and adult women as hirsutism, virilization, and oligomenorrhea or amenorrhea; these manifestations are due to milder cortisol deficiency.
Given the variety of presentations possible in 21-hydroxylase CAH, diagnosis typically depends upon clinical history and elevated concentrations of 17-hydroxyprogesterone (17-OHP) in blood specimens or dried blood spots. However, distinguishing heterozygotes from unaffected subjects based only on 17-OHP measurements can prove difficult. In order to further delineate the type of CAH in a patient, many laboratories offer various panels that also include androstenedione, cortisol, DHEA, testosterone and 11-deoxycortisol measurements. A less-well-known metabolite is 21-deoxycortisol, which is significantly elevated in cases of CAH but usually undetectable; this analytic issue occurs even when the most modern instrumentation is used for measurement.
In our laboratory, we modified an existing LC-MS/MS assay for 11-deoxycortisol and corticosterone to also concurrently measure 21-deoxycortisol. Analytical sensitivity for 21-deoxycortisol in this assay configuration was 10 ng/dL and precision ranged from 6.1 – 7.0%, while accuracy was between 91.6 – 102.7%. Given satisfactory performance of this assay, we further characterized 21-deoxycortisol concentrations in specimens from patients with two of the most common CYP21 gene mutations (In2G and I172N).
Literature search and review suggested that 21-deoxycortisol measurements after ACTH stimulation can detect more than 90% of LOCAH cases. Also, 21-deoxycortisol testing used in conjunction with 17-OHP testing provided an appropriate second tier test for confirming positive results after first tier screening. Comparisons of various metabolite concentrations (e.g., the molar ratio of the sum of the 21-deoxycortisol plus the 17-OHP, divided by cortisol) demonstrated a positive predictive value of 100%. Thus, 21-deoxycortisol measurements might assist with: 1) newborn screening for CAH where 17-OHP testing is not very specific; 2) prenatal diagnosis of CAH; and 3) the detection of LOCAH.
- Fiet et al. Comparison of Basal and Adrenocorticotropin-Stimulated Plasma 21-Deoxycortisol and 17-Hydroxyprogesterone Values as Biological Markers of Late-Onset Adrenal Hyperplasia. JCEM 1988(66):659-667.
- Speiser et al. Congenital Adrenal Hyperplasia Due to Steroid 21-Hydroxylase Deficiency: An Endocrine Society Clinical Practice Guideline. JCEM 2010 95(9):4133-4160.
- Janzen et al. Newborn Screening for Congenital Adrenal Hyperplasia: Additional Steroid Profile Using Liquid Chromatography – Tandem Mass Spectrometry. JCEM 2007 92(7): 2581-2589.
Thank you to Bill Curtin for his help with this work and to William Winter for his assistance with this blog post.