17-Hydroxyprogesterone (17-OH progesterone or 17OHP) is a C-21 steroid hormone produced in the adrenal gland and gonads, during the synthesis of glucocorticoids and sex steroids. It is derived from progesterone via 17-hydroxylase, a P450c17 enzyme, or from 17-hydroxypregnenolone via 3β-hydroxysteroid dehydrogenase/delta 5-4 isomerase. 17α -OHP has no defined physiologic role except as a precursor molecule. Serum 17α -OHP levels are age-dependent, with peak levels observed during fetal life and the immediate postnatal period. During the first week of life, serum 17α -OHP levels fall ~50-fold as compared to cord blood values. A small transient increase occurs in male infants 30-60 days postnatally. Levels for both sexes remain at constant low levels during childhood, and then progressively increase during puberty reaching adult levels of ~100 ng/dL (~3.03 nmol/l). As with cortisol, serum 17α -OHP levels normally have an ACTHdependent diurnal variation, with peak levels in the morning and a nadir at night. In addition, ovarian production of 17α -OHP increases during the luteal phase of the menstrual cycle. 17-hydroxyprogesterone is a natural progestin and in pregnancy increases in the third trimester primarily due to fetal adrenal production. Normal levels are 3-90 ng/dl in children, and in women, 15-70 ng/dl prior to ovulation, and 35-290 ng/dl during the luteal phase. Measurements of levels of 17-hydroxyprogesterone are useful in the evaluation of patients with suspected congenital adrenal hyperplasia as the typical enzymes that are defective, namely 21-hydroxylase and 11b-hydroxilase, lead to a build-up of 17OHP. In contrast, the rare patient with 17α-hydroxylase deficiency will have very low or undetectable levels of 17OHP. Elevated serum 17 α -OHP levels at baseline and/or after ACTH stimulation have also been reported in other forms of adrenal hyperplasia.

May be diagnosed by:  

• Determination of specific antibodies based on the ELISA technique
• Determination of specific antibodies based on the RIA-technique

17 OH Progesterone ELISA:

Competitive immunoenzymatic colorimetric method for quantitative determination of 17 α OH Progesterone in serum or plasma. 

Principle of the Assay:

α OH Progesterone antibodies (solid-phase). 17 α OH Progesterone in the sample competes with added horseradish peroxidase labelled 17 α OH Progesterone (enzyme-labelled antigen) for antibody binding. After incubation a bound/free separation is performed by solid-phase washing. The immune complex formed by enzyme-labelled antigen is visualized by adding Tetramethylbenzidine (TMB) substrate which gives a blue reaction product. The intensity of this product is inversely proportional to the amount of 17 α OH Progesterone in the sample. Sulphuric acid is added to stop the reaction. This produces a yellow endpoint colour. Absorption at 450 nm is read using an ELISA microwell plate reader.

Specific performance characteristics:   

Correlation with RIA performed on 36 samples is r = 0.993

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