The steroid 17-α-Hydroxyprogesterone (17-α-OHP) is produced by both the adrenal cortex and gonads. Even though 17-α-OHP has relatively little progestational activity, it is of intense clinical interest because it is the immediate precursor to 11-desoxycortisol (Cpd-S). Because Cpd-S is produced by 21-hydroxylation of 17-α-OHP, measurement of 17-α-OHP is a useful indirect indicator of 21-hydroxylase activity. In congenital 21-hydroxylase deficiency, the most common variety of congenital adrenal hyperplasia (CAH), 17-α-OHP is secreted in abundant excess. It is moderately elevated in the 11-β-hydroxylase deficiency as well. Measurement of 17-α-OHP is therefore valuable in the initial diagnosis of CAH.
Adult non-pregnant women: In adult non-pregnant women in the childbearing age group, 17-α-OHP concentrations vary over the menstrual cycle with luteal phase concentrations being higher than follicular phase concentrations. This is because 17-α-OHP is secreted parallel with progesterone from maturing follicles or from the corpus luteum. There is also a diurnal variation of 17-α-OHP concentrations. This rhythm is parallel with adrenal cortisol secretion such that maximum 17-α-OHP concentrations are measured in samples obtained between midnight and 8:00 am.
Adult males: There is little information available on the systematic variability of 17-α-OHP concentration in adult males.
Pregnant women and newborn children: The steroid 17-α-OHP is produced in large amounts by the fetus and the adrenals. It is secreted in abundance into both the fetal and maternal circulation. The maternal concentrations of 17-α-OHP increase very sharply after 32 weeks gestational age to about 4-fold above basal concentrations at term.
Clinical Applications
Congenital adrenal hyperplasia: The principal application of the 17-α-OHP RIA is in the diagnosis of CAH in newborns with ambiguous genitalia and in virilized adolescent girls. Since 17-α-OHP is the immediate precursor to 11-desoxycortisol, basal 17-α-OHP concentrations are sharply elevated in patients with 21-hydroxylase deficiency and to a lesser degree in patients with 11-hydroxylase deficiency. Because 17-α-OHP concentrations are so markedly elevated in newborns and adolescent girls afflicted with CAH, a single basal measurement is all that is normally required to make the diagnosis.
Late onset adrenal hyperplasia: More recently, 17-α-OHP concentrations have been utilized in the evaluation of androgenized women where late onset of 21-hydroxylase deficiency is suspected. This condition is clinically very subtile and since the presentation is the same as classical polycystic ovarian disease, basal plasma 17-α-OHP concentrations, unlike classical congenital adrenal hyperplasia, are normal. The diagnosis is made by administration of an ACTH stimulation test.
Other applications: Measurement of 17-α-OHP concentrations is also utilized in evaluation of both men and women with acne vulgaris, male pattern baldness and in some subtile forms of infertility. Experiences with these applications are very limited.