Assays / Hormones / 17a-Hydroxyprogesterone (serum)

Clinical Use

• Diagnosis of congenital adrenal hyperplasia due to 21-hydroxylase deficiency.
• Monitoring the response to corticosteroid therapy in congenital adrenal hyperplasia due to 21-hydroxylase deficiency.
• Identification of heterozygotes for congenital adrenal hyperplasia and diagnosis of mild congenital adrenal hyperplasia (also referred to as late-onset and cryptic forms).

17a-Hydroxyprogesterone is an intermediate in the biosynthesis of cortisol. Deficiency of either 11b- or 21-hydroxylase activities leads to an increased concentration of 17a-hydroxyprogesterone in the peripheral circulation. This test is less valuable in 11b-hydroxylase deficiency, where 11-deoxycortisol is the analyte of choice. 'Functional' deficiencies of 21-hydroxylase and 11b-hydroxylase have been described.

Patient Preparation
1. Diagnosis of congenital adrenal hyperplasia.
Take blood (l mL) into a plain tube before any emergency administration of corticosteroids and preferably in the early morning. Samples for this test should not be taken from newborn infants until more than 48h after birth.

All new cases should be confirmed by urine steroid profiling.
2. Monitoring response to treatment.
Take blood (1 mL) between 08.00h and 09.00h before initiation of treatment for the day and again 2h after the first dose of corticosteroid. Further samples may be taken through the day. Record the time of any therapy. Adequacy of treatment may be better judged if combined with the measurement of androstenedione.
3. Identification of heterozygotes and diagnosis of mild congenital adrenal hyperplasia.
In a female patient with menstrual cycles, the test should be carried out between 09.00h and 10.00h in the first five days following menstruation. Take blood (l mL) for baseline value. Inject adrenocorticotrophin (ACTH 1-24, Tetracosactrin Ciba, 0.25 mg i.m.). Take blood (1 mL) l h after injection.

Sample Preparation
Send serum samples (0.5 mL) to the SAS laboratory. Record on the SAS request form gestation at delivery, plasma electrolytes and any genital abnormality. For urgent requests (e.g. acutely ill infants) contact the laboratory before despatching the sample.

Reference Ranges
(Age related reference ranges for children may be available from each Centre.)

Infants (unstressed)	<13 nmol/L
Infants (stressed)	<40 nmol/L
Adult males	2 - 9 nmol/L
Adult females - follicular phase	2 - 6 nmol/L
(N.B. Higher levels occur in the luteal phase)
Patients with untreated 21-hydroxylase deficiency	usually >100 nmol/L

Values lh after ACTH:
Unaffected Adults: 3 - 30 nmol/L
Heterozygotes for 21-hydroxylase deficiency: 6 - 44 nmol/L
Patients with mild 21-hydroxylase deficiency: 63 - 470 nmol/L

Quality Assessment:
UK NEQAS

Centres offering the assay:
Cardiff, Leeds, London (St. Thomas'), London (UCLH)