17a Hydroxyprogesterone

Clinical Chemistry

Description

17a Hydroxyprogesterone (17-OHP) is a 21 carbon steroid produced by the adrenal glands, ovaries, testes and placenta as a precursor to steroid hormones. Measurement is of value in the diagnosis and management of congenital adrenal hyperplasia (CAH). CAH is caused by inherited defects in steroid biosynthesis, which result in a reduction in glucocorticoids and mineralocorticoids and elevated 17-OHP and androgens. This can lead to a life-threatening salt-wasting crisis in neonates and the virilisation of females. The commonest form of CAH is due to mutations in the steroid 21-hydroxylase gene (CYP21A2), which results in a blockage in the synthesis of cortisol and a compensatory increase in ACTH secretion. This leads to increased production of 17-OHP, which is metabolised to androstenedione and testosterone, resulting in hyperandrogenism. Other, much rarer, forms of CAH include 11-hydroxylase and 17-hydroxylase deficiency. Blood 17-OHP shows a diurnal variation similar to that of cortisol, with higher concentrations in the early morning than in the late afternoon. Like progesterone, 17-OHP increases during the luteal phase of the menstrual cycle and in pregnancy.

Indications

Neonates and children: classical congenital adrenal hyperplasia (CAH) caused by 21-hydroxylase deficiency or 11-hydroxylase deficiency. Adults: investigation of females with hirsutism or infertility which can be caused by adult-onset CAH

Sample Type

Serum, SST/Gel, minimum 1 mL (0.5 mL separated serum). For adult females a follicular phase specimen preferred.

Reference Range

Reference ranges are provided on the report. Alternatively, please contact the laboratory for current ranges.

Turnaround Time

Within 2 weeks

Testing Frequency

Fortnightly

External Notes

Neonates should be over 48hrs old before sample collection for this test.

Patient Preparation

None. 17 OHP may be measured as part of a short synacthen test if late onset CAH is suspected.

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17a Hydroxyprogesterone