The 17-OH Progesterone (17-OHP) LCMS test measures a steroid hormone using Liquid Chromatography-Mass Spectrometry (LCMS). This test evaluates hormone production pathways and detects potential issues with hormone synthesis, especially those related to the adrenal glands.
What is 17-OH Progesterone?
17-Hydroxyprogesterone (17-OHP) is a steroid hormone produced primarily in the adrenal glands. Smaller amounts are also made in the gonads (ovaries or testes) and the placenta during pregnancy. 17-OHP serves as a precursor for other essential hormones. It is an intermediate in the biosynthesis of cortisol and is converted to cortisol through several enzymatic steps, notably by the enzymes 21-alpha hydroxylase and 11-beta hydroxylase. Abnormal 17-OHP levels can indicate a problem within this hormone production pathway, often due to an enzyme deficiency.
Why This Test is Important
Measuring 17-OHP levels is particularly important for screening and diagnosing Congenital Adrenal Hyperplasia (CAH), a genetic disorder. In CAH, the adrenal glands cannot produce enough cortisol, usually because of a missing or deficient enzyme, most commonly 21-hydroxylase. This enzyme deficiency causes 17-OHP to build up in the blood. Newborn screening programs in many countries, including all U.S. states, routinely test 17-OHP levels to identify CAH early. Early detection of CAH, especially the severe salt-wasting form, is important to prevent life-threatening complications such as dehydration, low blood pressure, and shock in infants. The test can also help identify milder forms of CAH in children or adults who may present with symptoms like early puberty, irregular periods, or excessive hair growth. Beyond CAH, 17-OHP testing can also be used to evaluate other adrenal gland disorders or certain types of ovarian tumors that exhibit endocrine activity.
The Accuracy of LCMS Testing
Liquid Chromatography-Mass Spectrometry (LCMS) is a precise laboratory method for measuring 17-OHP levels. This technique combines liquid chromatography, which separates components in a sample, with mass spectrometry, which identifies and quantifies them based on their mass-to-charge ratio. This dual approach offers advantages over older methods like immunoassays. Immunoassays, while used for initial screening, can produce false positive results because their antibodies may cross-react with other hormones. LCMS provides superior specificity and sensitivity, accurately distinguishing 17-OHP from similar steroids. This accuracy is valuable in newborn screening, where LCMS confirms positive immunoassay results and reduces false positives.
Understanding Your Test Results
Interpreting 17-OHP test results requires careful consideration by a healthcare professional, as normal ranges can vary based on factors like age, sex, and the specific laboratory performing the test. In babies older than 24 hours, levels typically fall below 400 to 600 nanograms per deciliter (ng/dL), while in prepubertal children, levels are generally around 100 ng/dL. Adult levels are below 200 ng/dL. Elevated 17-OHP levels often suggest the presence of Congenital Adrenal Hyperplasia (CAH), particularly the most common type caused by 21-hydroxylase deficiency. In infants with CAH, 17-OHP levels can range significantly, from approximately 2,000 to 40,000 ng/dL. Moderately increased levels might indicate a milder form of CAH or another enzyme deficiency, such as 11-beta-hydroxylase deficiency. If initial results are unclear, or if a person has symptoms despite a seemingly normal 17-OHP level, an ACTH stimulation test may be performed to further assess adrenal function.
What Happens After Diagnosis
If elevated 17-OHP levels lead to a diagnosis of Congenital Adrenal Hyperplasia (CAH), further confirmatory tests, including genetic testing, may be recommended to identify the specific enzyme deficiency. Management of CAH typically involves lifelong hormone replacement therapy, including daily oral medications like hydrocortisone to replace deficient cortisol and fludrocortisone to replace aldosterone, especially in salt-wasting forms. During periods of illness or stress, higher doses of medication may be necessary. Ongoing medical care and regular blood tests monitor hormone levels and adjust medication doses for proper growth and development and to prevent complications.