17-Hydroxyprogesterone and Adrenal Androgens

17-hydroxyprogesterone (17-OHP) is an intermediate in cortisol biosynthesis. In congenital adrenal hyperplasia (CAH) from 21-hydroxylase deficiency (CYP21A2, about 95% of cases), cortisol synthesis is blocked, ACTH rises, and the adrenal produces excess 17-OHP and androgens (androstenedione, testosterone, DHEA and its sulphate).

Salt wasting from aldosterone deficiency occurs in the severe form. 17-OHP is measured by immunoassay on a blood spot (newborn screening) or serum, and by liquid chromatography with mass spectrometry, which is more accurate. Androstenedione, DHEA sulphate and testosterone complete the adrenal androgen assessment.

The tests screen for and diagnose CAH, investigate hirsutism, virilisation, precocious puberty and amenorrhoea, and monitor treatment. Adrenal androgens also help to separate adrenal from ovarian androgen excess.

Classic CAH affects about 1 in 10 000 to 18 000 live births, and non-classic (late onset) CAH affects 1 in 200 to 1000 people, up to 1 in 30 in some groups (Ashkenazi Jewish, Hispanic and Mediterranean). It accounts for 1 to 10% of women with hyperandrogenism.

Indications. Ambiguous genitalia in a newborn, salt wasting crisis in an infant, newborn screening, early pubic hair, rapid growth or advanced bone age, hirsutism, acne, oligomenorrhoea or infertility in a woman, virilisation, adrenal mass, family history of CAH, and monitoring of glucocorticoid treatment.

Specimen. Serum collected in the early morning (7 to 9 am), because 17-OHP and androgens have a circadian rhythm and peak at that time. In women, take in the early follicular phase (days 3 to 5), since luteal progesterone and 17-OHP are higher. Newborn heel prick blood spot at 48 to 72 hours (not before 24 hours). Record glucocorticoid and contraceptive use.

Ranges depend on age, sex, cycle phase and method. Conversion: 17-OHP ng/mL multiplied by 3.03 gives nmol/L.

17-OHP.

• Adults, follicular phase or men, morning: under 6 nmol/L (under 2 ng/mL).
• Non-classic CAH: basal over 6 to 15 nmol/L (over 2 to 5 ng/mL) suggests it, and over 30 nmol/L (over 10 ng/mL) after tetracosactide stimulation confirms it.
• Classic CAH: basal often over 100 nmol/L, and in infants over 300 nmol/L (over 100 ng/mL).
• Newborn screening cut offs vary with gestational age and weight, as preterm and sick infants have false positives.

Short ACTH (tetracosactide) stimulation test. Serum 17-OHP at 0 and 60 minutes after 250 microg tetracosactide. A peak over 30 nmol/L (over 10 ng/mL) indicates CAH, 15 to 30 nmol/L suggests a heterozygous carrier, and under 15 nmol/L is normal. Cortisol is measured at the same time to assess adrenal reserve.

Androstenedione. Women: 2 to 8 nmol/L, men: 2 to 9 nmol/L. Raised in CAH, polycystic ovary syndrome, adrenal and ovarian tumours, and Cushing syndrome. Lowered in adrenal insufficiency and with glucocorticoid treatment.

DHEA sulphate (DHEAS). Stable through the day and long acting. Range varies strongly with age (peak at 20 to 30 years, 2 to 10 micromol/L in women) and falls to low values in older adults. Raised: adrenal tumours (very high, over 20 micromol/L, suggests adrenal carcinoma), CAH, polycystic ovary syndrome, premature adrenarche, and Cushing disease. Lowered: adrenal insufficiency, hypopituitarism, ageing, glucocorticoid treatment and oral contraception.

Testosterone. Measured alongside the adrenal androgens to assess androgen excess. Adrenal causes tend to raise DHEAS and androstenedione with a modest rise in testosterone, and ovarian causes raise testosterone.

Other CAH forms. 11-beta-hydroxylase deficiency (high 11-deoxycortisol and deoxycorticosterone, hypertension, hypokalaemia), 3-beta-hydroxysteroid dehydrogenase deficiency (high 17-hydroxypregnenolone and DHEA), 17-alpha-hydroxylase deficiency (low androgens, hypertension, hypokalaemia, absent puberty), and lipoid CAH. A urinary steroid profile or serum steroid profile by mass spectrometry separates these.

Classic salt wasting CAH. Presents in the first 1 to 3 weeks with vomiting, poor feeding, weight loss, hypotension, hyponatraemia (under 130 mmol/L), hyperkalaemia, hypoglycaemia and a metabolic acidosis, with high renin and 17-OHP, and low cortisol and aldosterone. Girls have ambiguous genitalia (46,XX with virilisation), and boys may be missed until a crisis.

Classic simple virilising CAH. Virilisation without salt loss, accelerated growth, and advanced bone age in childhood.

Non-classic CAH. Premature pubarche, hirsutism, acne, menstrual irregularity and subfertility, with a mildly raised 17-OHP that rises after stimulation.

Monitoring treatment. Glucocorticoid dose is adjusted by morning (pre-dose) 17-OHP (aim for 12 to 36 nmol/L, or about 4 to 12 ng/mL, not normal, to avoid over treatment), androstenedione (in the upper normal range), plasma renin (high normal), growth velocity and bone age in children. Suppression of 17-OHP to normal means overtreatment with Cushingoid effects.

Differential of androgen excess.

• Polycystic ovary syndrome: mildly raised testosterone and androstenedione, normal or mildly raised 17-OHP, DHEAS normal or mild rise.
• Adrenal tumour: very high DHEAS and testosterone, with rapid virilisation.
• Ovarian tumour: very high testosterone, with normal DHEAS.
• Cushing syndrome: raised androgens with cortisol excess.
• Hyperprolactinaemia and thyroid disease: modest androgen effects.

Critical values and findings needing immediate action.

• Hyponatraemia, hyperkalaemia, hypoglycaemia and shock in a newborn or infant with ambiguous genitalia or a positive screen: adrenal crisis, which needs immediate hydrocortisone, saline and glucose, with samples taken first if this does not delay treatment.
• Raised 17-OHP on newborn screening in a sick infant.
• Rapid virilisation with total testosterone over 5 nmol/L or DHEAS over 20 micromol/L: tumour until proven otherwise.
• Pregnancy in a woman with CAH, needing stress cover and prenatal advice.

Interferences and pitfalls.

• Immunoassays for 17-OHP cross-react with other steroids, especially in newborns, giving false positives in preterm, sick or low-birth-weight infants. Mass spectrometry as a second tier test reduces this.
• Timing: later in the day, luteal phase, and stress give higher values. Morning follicular samples are used.
• Glucocorticoids, oral contraceptives and dexamethasone suppress adrenal androgens and 17-OHP, so they are stopped (where safe) before testing.
• Antenatal dexamethasone can cause false negative newborn screening.
• A normal basal 17-OHP does not exclude non-classic CAH, and stimulation testing is needed when suspicion is high.
• Heterozygous carriers have a mildly raised stimulated 17-OHP, and genetic testing differentiates.
• Interpretation in obesity, polycystic ovary syndrome and Cushing syndrome overlaps.

Special groups.

• Newborns: screening at 48 to 72 hours and prompt confirmatory testing. Salt wasting crises appear at 1 to 3 weeks if missed.
• Children: premature pubarche and tall stature with advanced bone age.
• Pregnancy: placental 17-OHP and androgens rise, and the diagnosis in pregnancy is made by genetic testing.
• Women: late onset CAH accounts for a small share of hyperandrogenism and subfertility.
• Regions: the frequency of CAH is high in some isolated populations (Yupik Eskimos, Reunion Island) and screening is not available in many settings.

Follow up tests. Short ACTH stimulation test with 17-OHP and cortisol, sodium, potassium, glucose, renin and aldosterone, androstenedione, DHEAS, testosterone, urinary or serum steroid profile by mass spectrometry, CYP21A2 gene sequencing, bone age radiograph, pelvic and adrenal imaging, karyotype for ambiguous genitalia, and family screening.