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Hormones

17-OH-progesterone: cycle phase, pregnancy and the mild form of CAH

17-OH-progesterone is a substance in the adrenal gland that serves as an intermediate product in the making of cortisol; the enzyme 21-hydroxylase converts it into 11-deoxycortisol. In the second half of the menstrual cycle the value is higher, which shows in the separate limits laboratories use for that phase.

When 21-hydroxylase works too little, as in congenital adrenal hyperplasia (CAH), 17-OH-progesterone builds up and part of it is converted into male hormones; in women with the mild form, the Endocrine Society guideline names excess hair growth (hirsutism). Only a blood test shows how much 17-OH-progesterone there is.

17-OH-progesterone is measured in nanomoles per litre: for women aged 18 to 50, Unilabs uses 0.45 to 3 nmol/l in the follicular phase, the first half of the cycle, and 1.0 to 8.5 nmol/l in the luteal phase, the second half after ovulation.

Doctor's Assessment Included

17-OH-progesterone is an intermediate step in the making of cortisol in the adrenal gland, and the standard measurement for establishing congenital adrenal hyperplasia (CAH). The limit differs per laboratory, age, sex and cycle phase.

  • The Endocrine Society guideline advises drawing blood before 8 am, and in women who menstruate early in the follicular phase.
  • In the luteal phase the value is higher: Diagnostiek voor U then uses < 8.78 nmol/L, against < 2.12 nmol/L in the follicular phase.
  • A value measured at a random time can be normal in the mild form of CAH.

Reference Ranges

Female
nmol/L
Low 0.3 Normal 7.5 High

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

Check your own value

17-OH Progesterone: what Dutch laboratories use

Reference ranges by group, in nmol/L
Star-shl · Female · 20–29 years · a limit, not a range < 2.54 nmol/L
2.54
Star-shl · Female · 30–39 years · a limit, not a range < 2.57 nmol/L
2.57
Star-shl · Female · 40–49 years · a limit, not a range < 2.36 nmol/L
2.36
Star-shl · Female · 50 years and older · a limit, not a range < 2.05 nmol/L
2.05
Unilabs · Female · 18–50 years · follicular phase 0.45–3.00 nmol/l
0.45 3
Unilabs · Female · 18–50 years · luteal phase 1.0–8.5 nmol/l
1 8.5
Unilabs · Female · 50 years and older · a limit, not a range < 1.6 nmol/l
1.6
Certe · Female · 20–49 years 0.23–7.56 nmol/L
0.23 7.56
Certe · Female · 49–59 years 0.32–5.24 nmol/L
0.32 5.24
Certe · Female · 59–70 years 0.31–3.75 nmol/L
0.31 3.75
Certe · Female · 70–79 years 0.36–2.36 nmol/L
0.36 2.36
Diagnostiek voor U · Female · 20–29 years · a limit, not a range < 2.54 nmol/L
2.54
Diagnostiek voor U · Female · 30–39 years · a limit, not a range < 2.57 nmol/L
2.57
Diagnostiek voor U · Female · 40–49 years · a limit, not a range < 2.36 nmol/L
2.36
Diagnostiek voor U · Female · 50 years and older · a limit, not a range < 2.05 nmol/L
2.05
Diagnostiek voor U · Female · a limit, not a range · follicular phase < 2.12 nmol/L
2.12
Diagnostiek voor U · Female · a limit, not a range · luteal phase < 8.78 nmol/L
8.78
0 9.66 nmol/L

Source: Star-shl

Source: Unilabs

Source: Certe

Source: Diagnostiek voor U

Each value as the laboratory itself publishes it, retrieved in 2026.

17-OH Progesterone: what this test measures

A 17-OH-progesterone measurement gives the amount of 17-hydroxyprogesterone in the serum in nanomoles per litre (nmol/L). In women who menstruate, the Endocrine Society guideline advises measuring early in the follicular phase, and the guideline notes that the result of such a measurement can differ per measuring method.

17-OH Progesterone: why this value matters

17-OH-progesterone helps detect the mild, nonclassic form of CAH, which according to the Endocrine Society guideline gives a varying excess of male hormones and sometimes runs without symptoms. According to a genetic analysis the guideline cites, the mild form occurs in about 1 in 200 people in the US population.

17-OH Progesterone: how the blood test works

Referral
No GP referral needed. After the order we arrange the referral through ZorgDomein, within one business day; orders after 17:00 or at the weekend start on the next business day. ZorgDomein emails a barcode, and that barcode is what the draw site needs.
The draw
A blood draw from a vein in the arm, at a partner laboratory's draw site. No home kit, no finger prick.
Where
650+ draw sites run by independent laboratories across the Netherlands. Draw sites

17-OH Progesterone: when is testing worthwhile?

In women who menstruate, 17-OH-progesterone is measured early in the follicular phase according to the Endocrine Society guideline, with blood drawn before 8 am. A measurement in the luteal phase comes out higher: Diagnostiek voor U then uses < 8.78 nmol/L, against < 2.12 nmol/L in the follicular phase, which is why the moment in the cycle counts when reading the result.

17-OH Progesterone: symptoms of a high or low value

Low Levels

A low 17-OH-progesterone at Unilabs is, for women aged 18 to 50, a value below 0.45 nmol/l in the follicular phase or below 1.0 nmol/l in the luteal phase; Star-SHL and Diagnostiek voor U name no lower limit for women. A condition that goes with a low value is not in the Endocrine Society guideline.

High Levels

In women with a high 17-OH-progesterone from the mild form of CAH, the Endocrine Society guideline names excess hair growth (hirsutism), and in adolescents with that mild form irregular periods and acne.

17-OH Progesterone: causes of a low or high value

What raises the value

  • Congenital adrenal hyperplasia from 21-hydroxylase deficiency

    According to the Endocrine Society guideline, CAH is caused in about 95% of cases by a fault in the gene for 21-hydroxylase; that enzyme converts 17-OH-progesterone, and with a shortage 17-OH-progesterone builds up.

  • Mild (nonclassic) CAH

    In the mild form, a 17-OH-progesterone measured at a random time can be normal; that is why the guideline advises blood drawn before 8 am.

  • Other adrenal enzyme shortages

    According to the guideline, 17-OH-progesterone can also be raised with a shortage of 11-beta-hydroxylase and, more rarely, of 3-beta-hydroxysteroid dehydrogenase or P450 oxidoreductase.

  • Pregnancy

    According to the guideline, 17-OH-progesterone in the mother is raised in a normal pregnancy.

  • Second half of the menstrual cycle

    In the luteal phase the value is higher: Unilabs then uses 1.0 to 8.5 nmol/l, against 0.45 to 3 nmol/l in the follicular phase, for women aged 18 to 50.

17-OH Progesterone: lifestyle and this value

With a raised 17-OH-progesterone, a doctor establishes the cause, and the treatment of women with the mild form of CAH depends on the symptoms, according to the Endocrine Society guideline. For excess hair growth in women with the mild form, the guideline calls a contraceptive pill, with or without an anti-androgen that blocks the action of male hormones, likely the best approach. In women with the mild form who are infertile or have had a miscarriage before, the guideline recommends a glucocorticoid that does not cross the placenta.

17-OH Progesterone: frequently asked questions

Is 17-OH-progesterone higher during pregnancy?

Yes, in a normal pregnancy 17-OH-progesterone in the mother is raised, according to the Endocrine Society guideline. For that reason the guideline does not use the value to follow the treatment of CAH during pregnancy.

Is 17-OH-progesterone the same as progesterone?

No, 17-OH-progesterone and progesterone are two different substances: according to the Endocrine Society guideline, the enzyme 21-hydroxylase converts 17-OH-progesterone into 11-deoxycortisol and progesterone into deoxycorticosterone. Star-SHL has a separate determination for each of the two.

Does the mild form of CAH raise the chance of a miscarriage?

The three studies the Endocrine Society guideline cites on the miscarriage chance in the mild form of CAH, an inherited condition in which 17-OH-progesterone builds up in the adrenal gland, disagree. Two retrospective studies found a miscarriage chance of about 25% without a glucocorticoid and 6% with one in women with the mild form; the third study found no difference in miscarriage rate between treated and untreated women.

17-OH Progesterone: sources

  1. Unilabs, Bepalingenklapper (referentiewaarden per bepaling), bepalingenklapper.nl, geraadpleegd 2026-10-01 (retrieved 2026) bepalingenklapper.nl
  2. Certe, Bepalingenwijzer (referentiewaarden per bepaling), bepalingenwijzer.certe.nl, geraadpleegd 2026-10-01 (retrieved 2026) bepalingenwijzer.certe.nl
  3. Diagnostiek voor U, eLabgids (Referentiewaarden DvU), diagnostiek.getincontrol.eu, geraadpleegd 2026-10-01 (retrieved 2026) diagnostiek.getincontrol.eu
  4. Star-shl, Labbepalingen (referentiewaarden per bepaling), star-shl.nl, geraadpleegd 2026-10-01 (retrieved 2026) star-shl.nl
  5. Speiser PW et al. Congenital Adrenal Hyperplasia Due to Steroid 21-Hydroxylase Deficiency: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab 2018;103(11):4043-4088. (retrieved 2026) pmc.ncbi.nlm.nih.gov

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