Adrenal

17a-OH-Progesterone figure 14-9 Pathways and anatomical compartmentalization of the production of the C-21 progestins, particularly progesterone, 17a-hydroxyprogesterone, and 16a;-hydroxyproges-terone in the human fetal placental unit. This figure was derived in part from Buster, J. E., and Marshall, J. R. (1979). Conception, gamete and ovum transport, implantation, fetal placental hormones, hormonal preparation for parturition and parturition control. In "Endocrinology" (L. J. DeGroot, G. F. Cahill, L. Martini, D. H. Nelson, W. D. Odell, J. T. Potts, E. Steinberger, and A. I. Winegrad, eds.), Vol. 3, pp. 1595-1612. Grune & Stratton, New York.

figure 14-10 Pathways and anatomical compartmentalization of the production of the C-18 estrogens (estradiol, estrone, estriol, and estetrol) in the human fetal placenta unit. This figure was derived from Buster, J. E., and Marshall, J. R. (1979). Conception, gamete and ovum transport, implantation, fetal placental hormones, hormonal preparation for parturition and partition control. In "Endocrinology" (L. J. DeGroot, G. F. Cahill, L. Martini, D. H. Nelson, W. D. Odell, J. T. Potts, Jr., E. Steinberger, and A. I. Winegrad, eds.), Vol. 3, pp. 1595-1612. Grune & Stratton, New York.

figure 14-10 Pathways and anatomical compartmentalization of the production of the C-18 estrogens (estradiol, estrone, estriol, and estetrol) in the human fetal placenta unit. This figure was derived from Buster, J. E., and Marshall, J. R. (1979). Conception, gamete and ovum transport, implantation, fetal placental hormones, hormonal preparation for parturition and partition control. In "Endocrinology" (L. J. DeGroot, G. F. Cahill, L. Martini, D. H. Nelson, W. D. Odell, J. T. Potts, Jr., E. Steinberger, and A. I. Winegrad, eds.), Vol. 3, pp. 1595-1612. Grune & Stratton, New York.

60 ng/ml at weeks 6-36 of gestation. Up to the first 8-12 weeks of gestation the maternal ovary is the principal site of 17a-hydroxyprogesterone. After the first trimester, the placenta uses the precursor 17-hydroxy-A5-pregnenolone produced from A5 C-21 sul-foconjugates in the fetal adrenal cortex to produce 17-hy dr oxyprogesterone.

16a-Hydroxyprogesterone plasma levels gradually rise from 0.5 ng/ml at conception to a level of 120140 ng/ml by 32 weeks of gestation. The precise bio-synthetic pathway of 16a-hydroxyprogesterone is not known; it is believed that the fetal liver produces 16-hydroxy-A5-pregnenolone sulfate and that this is converted by the placenta into 16a-hydroxyprogesterone, which is then available to both mother and fetus. There is no known specific biological response attributable to 16a-hydroxyprogesterone.

c. Production of Estrogens

Throughout the course of pregnancy there are four principal forms of the C-18 estrogens present. At parturition the relative serum concentrations are as follows: estradiol, 10-30 ng/ml; estriol 5-10 ng/ml; estrone, 5-8 ng/ml; and estetrol, 2-4 ng/ml. Estetrol is 15, 16-dihydroxyestradiol. Figure 14-10 summarizes their pathways of biosynthesis.

By the end of the first trimester the placenta is the principal site of biosynthesis of estradiol and estrone. Estriol is produced largely from the placental conversion of 16-hydroxydehydroepiandrosterone sulfate derived successively from the fetal liver and adrenals. Finally, estetrol is believed to be largely produced in the fetal compartment from placentally generated estriol.

Since the fetus plays a key role in the production of estetrol and estriol, the measurement of the maternal blood levels of these steroids has been proposed to provide some insight into fetal well-being. Thus, deteriorating fetoplacental health in the third trimester is often associated with falling unconjugated maternal serum estriol or estetrol concentrations.

d. Production of Androgens

The principal C-19 androgen in the pregnant female is dehydroepiandrosterone sulfate; prior to conception the maternal serum level is 1600 ng/ml, and this decreases throughout gestation to a value of 800 ng/ ml at parturition. As described in Figure 14-11, the principal source of androgens in the female is from the maternal adrenal cortex; here cholesterol is converted to pregnenolone and then finally to dehydroepiandrosterone sulfate. The fall in blood levels of dehydroepiandrosterone sulfate is believed to reflect an increased metabolic clearance rate due to a significant

Cholesterol

Cholesterol

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Cure Tennis Elbow Without Surgery

Cure Tennis Elbow Without Surgery

Everything you wanted to know about. How To Cure Tennis Elbow. Are you an athlete who suffers from tennis elbow? Contrary to popular opinion, most people who suffer from tennis elbow do not even play tennis. They get this condition, which is a torn tendon in the elbow, from the strain of using the same motions with the arm, repeatedly. If you have tennis elbow, you understand how the pain can disrupt your day.

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