17alpha-hydroxyprogesterone in blood

17-hydroxyprogesterone is a precursor of cortisol that has a natriuretic effect. The hormone is produced in the adrenal glands, ovaries, testicles, and placenta. As a result of hydroxylation, 17-hydroxyprogesterone is converted into cortisol.

Determination of 17-hydroxyprogesterone in the blood plays a leading role in the diagnosis of adrenogenital syndrome, which is accompanied by hyperproduction of one group of hormones by the adrenal cortex and decreased secretion of another. Adrenogenital syndrome is based on hereditary deficiency of various enzymes involved in the biosynthesis of steroid hormones. There are several forms of adrenogenital syndrome, the clinical manifestations of which depend on the deficiency of a specific enzyme: 21-hydroxylase, 11β-hydroxylase, 3β-oxide dehydrogenase, P ₄₅₀ SCC (20,22-despolase), 17-hydroxylase. Common to all forms of adrenogenital syndrome is a violation of the synthesis of cortisol, which regulates the secretion of ACTH according to the principle of the feedback mechanism.

Reference values (norm) of 17-hydroxyprogesterone concentration in blood serum

Age	17-GPG, nmol/l
Children, puberty:
Boys	0.1-2.7
Girls	0.1-2.5
Women:
Follicular phase	0.4-2.1
Luteal phase	1.0-8.7
Postmenopause	<2.1

A decrease in the blood cortisol level promotes increased secretion of ACTH by the anterior pituitary gland, which leads to hyperfunction of the adrenal glands, its hyperplasia and increased secretion of steroid precursors from which androgens are synthesized. An increased concentration of androgens in the blood (unlike cortisol) does not reduce the secretion of ACTH by the pituitary gland. As a result, an excess amount of 17-hydroxyprogesterone accumulates in the adrenal cortex, both due to its insufficient conversion to cortisol and due to increased formation.

Most often (80-95% of all cases) a deficiency of 21-hydroxylase is detected, which is necessary for the conversion of 17-hydroxyprogesterone into 11-deoxycortisol and then into cortisol. Every third patient with this type of enzymatic defect has severe disturbances in the synthesis of cortisol and insufficient synthesis of aldosterone. Clinically, this is expressed in the salt-wasting syndrome. The body is unable to retain sodium, resulting in its loss in the urine, dehydration, and collapse. Death of sick children usually occurs in the first weeks of life.

The most important role in the diagnosis of adrenogenital syndrome caused by 21-hydroxylase deficiency is played by the determination of 17-hydroxyprogesterone, DHEAS and testosterone in the blood and the excretion of 17-KS in the urine, which can exceed the norm by 5-10 times or more. The concentration of 17-hydroxyprogesterone in the blood above 24 nmol/l confirms the diagnosis of congenital adrenal hyperplasia. If it is 9-24 nmol/l, an ACTH test is indicated for the differential diagnosis of polycystic ovary syndrome and adrenogenital syndrome. It should be remembered that in the non-classical form of 21-hydroxylase deficiency, the basal concentration of 17-hydroxyprogesterone in the blood can be below 9 nmol/l. In this regard, if adrenogenital syndrome is suspected, the ACTH test is carried out even with a low basal concentration of 17-hydroxyprogesterone. Normally, after 60 minutes, the concentration of 17-hydroxyprogesterone usually does not reach 12 nmol/l, with the classical form of adrenogenital syndrome it exceeds 90 nmol/l, with the non-classical form - 45 nmol/l. In heterozygous carriers of the mutant gene encoding 21-hydroxylase, the concentration of 17-hydroxyprogesterone in the blood after stimulation with ACTH increases to 30 nmol/l.

One of the reasons for the increased formation of 17-hydroxyprogesterone may be tumors of the adrenal cortex. An effective method of differential diagnosis is a dexamethasone test. Before the test, the patient's blood is taken to determine 17-hydroxyprogesterone, and a day before the test, a daily urine sample is collected to determine 17-KS. Adults are prescribed 2 mg of dexamethasone orally every 6 hours after meals for 48 hours. After finishing taking dexamethasone, blood is taken again and a daily urine sample is collected. In case of adrenogenital syndrome, the test is positive - the concentration of 17-hydroxyprogesterone in the blood drops sharply, and the excretion of 17-KS with urine decreases by more than 50%. In case of tumors (androsteromas, arrhenoblastomas), the test is negative, the hormone content does not decrease or decreases slightly.

[ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ], [ 6 ], [ 7 ], [ 8 ], [ 9 ]