17alpha-hydroxyprogesterone in the blood

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

The determination of 17-hydroxyprogesterone in the blood plays a leading role in the diagnosis of adrenogenital syndrome, which is accompanied by hyperproduction of the adrenal glands of hormones of one group and a decrease in the secretion of the other. At the heart of adrenogenital syndrome lies the hereditary insufficiency 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, pubertal age:
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

Reducing the level of cortisol in the blood contributes to the increased allocation of the anterior lobe of the pituitary ACTH, which leads to hyperfunction of the adrenal glands, its hyperplasia and increased secretion of steroid precursors, from which androgens are synthesized. Increased concentration in the blood of androgens (in contrast to cortisol) does not reduce the release of the pituitary ACTH. As a result, an excessive amount of 17-hydroxyprogesterone accumulates in the adrenal cortex, both because of its insufficient conversion to cortisol, and because of increased formation.

Most often (80-95% of all cases) show a deficiency of 21-hydroxylase, necessary for the conversion of 17-hydroxyprogesterone to 11-deoxycortisol and then to cortisol. Each third patient with this type of enzyme defect is observed gross violations of cortisol synthesis and inadequate synthesis of aldosterone. Clinically, this is expressed in the loss of salt syndrome. The body is unable to retain sodium, which results in loss of it in the urine, dehydration, collapse. The death of sick children usually occurs in the first weeks of life.

The most important role in the diagnosis of adrenogenital syndrome due to 21-hydroxylase deficiency is the determination of 17-hydroxyprogesterone, DHEAS and testosterone in the blood and excretion of 17-CS with 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, a trial with ACTH is shown for differential diagnosis of polycystic ovary syndrome and adrenogenital syndrome. It should be remembered that with a nonclassical form of 21-hydroxylase deficiency, the basal concentration of 17-hydroxyprogesterone in the blood may be below 9 nmol / L. In connection with this, with a suspected adrenogenital syndrome, a test with ACTH is performed even at 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 exceeding 90 nmol / l, with 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 of ACTH increases to 30 nmol / l.

One of the reasons for increasing the formation of 17-hydroxyprogesterone may be tumors of the adrenal cortex. An effective method of differential diagnosis is a test with dexamethasone. Before the sample, blood is taken from the patient to determine 17-hydroxyprogesterone, and daily urine is collected a day before the sample to determine 17-CS. Adults are given oral 2 mg dexamethasone every 6 hours after a meal for 48 hours. After the end of taking dexamethasone, the blood is taken again and the urine is collected 24 hours. In adrenogenital syndrome, the sample is positive - the concentration of 17-hydroxyprogesterone in the blood drops sharply, and the excretion of 17-CS with urine decreases by more than 50%. In tumors (androsteromas, arrenoblastomas), the sample is negative, the content of hormones does not decrease or decreases slightly.

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