17a-Hydroxyprogesterone in serum

17-GPG 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, 17-GPG is converted to cortisol. The reference concentrations of 17-GPH in serum are given in the table.

The determination of 17-GPG in the blood plays a leading role in the diagnosis of ACS, which is accompanied by hyperproduction of the adrenal glands of one group of hormones and a decrease in the secretion of the other. At the heart of ACS is the hereditary insufficiency of various enzymes involved in the biosynthesis of steroid hormones. There are several forms of ACS, the clinical manifestations of which depend on the deficiency of a particular enzyme: 21-hydro-xylose, 11b-hydroxylase, 3p-oxide dehydrogenase, P4508SS( 20.22 desp-laz), 17-hydroxylase. Common to all forms of ACS is a violation of the synthesis of cortisol, which regulates the secretion of ACTH by the principle of the feedback mechanism.

Table Reference concentrations of 17-GPH in the blood serum

Table Reference values ​​for the concentration of 17-GPH in the blood serum

Reducing the cortisol in the blood contributes to the increased allocation of the anterior lobe of the pituitary ACTH, leading to adrenal hyperfunction, its hyperplasia and increased secretion of steroid precursors,of 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-GPG 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 needed to convert 17-GPG to 11-deoxy-cortisol 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 determination of 17-GPG, DHEAS and testosterone in the blood and the excretion of 17-CS with urine, which can exceed the norm by 5-10 times or more, plays an important role in the diagnosis of ACS due to the deficiency of 21-hydroxylase. The concentration of 17-GPG in the blood above 24 nmol / l confirms the

diagnosis of congenital adrenal hyperplasia. If it is 9-24 nmol / l, a test with ACTH is shown for differential diagnosis of polycystic ovary syndrome and ACS.It should be remembered that with a nonclassical form of 21-hydroxylase deficiency, the basal concentration of 17-GPH in the blood may be below 9 nmol / L.In connection with this, with the suspicion of ACS, the ACTH test is performed even at a low basal concentration of 17-GPH.Normally, after 60 minutes, the concentration of 17-GPH usually does not reach 12 nmol / l, with the classical form of ACS greater than 90 nmol / l, with non-classical form - 45 nmol / l. In heterozygous carriers of the mutant gene encoding 21-hydroxylase, the concentration of 17-GPG in the blood after stimulation of ACTH increases to 30 nmol / L.

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