Placenta hormones

Chorionic gonadotropin (CG) is produced in the placenta. Together- with the pituitary hormones, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), it constitutes the glycoprotein family of gonadotropins. The actions of CG are mediated by the LH receptor, both belonging to the superfamily of G-protein Coupled Receptors. 

Chorionic gonadotropin (HCG) is extracted from human placentas. The actions of HCG are identical to those of the pituitary LH. The hormone is used to induce ovulation in anovulatory women. This drug is also used for the treatment of prepubertal cryptorchism (failure of the testes to descend into the scrotum) and in men to treat selected cases of hypogonadotropic hypogonadism. 

The estrogens are a family of hormones synthesized in a variety of tissues. 17P-Estradiol is the primary estrogen of ovarian origin. In some species, estrone, synthesized in numerous tissues, is more abundant. In pregnancy, relatively more estriol is produced, and this comes from the placenta. The general pathway and the subcellular localization of the enzymes involved in the early steps of estradiol synthesis are the same as those involved in androgen biosynthesis. Features unique to the ovary are illustrated in Figure 42-7. 

Human chorionic gonadotropin A hormone secreted by the placenta that is used to aid in the determination of pregnancy. 

HCH also penetrates the placenta barrier [A96, A101]. Complications during pregnancy occurred 1.5 times more frequently in the 213 women whose blood contained HCH than in the 89 women with no signs of this insecticide (78.3% and 58.4% respectively). It is especially significant that twice as many women with HCH in their blood spontaneously miscarried during the first trimester as those without HCH (7.5% and 3.4% respectively). Causal factors included disruptions in prenatal fetal development, and disruptions in women s hormonal systems under the effect of HCH [A96]. Postpartum complications in women who had HCH in their blood were 2.5... 

Steroid hormones are produced by the adrenal cortex, testes, ovaries, and placenta. Synthesized from cholesterol, these hormones are lipid soluble therefore, they cross cell membranes readily and bind to receptors found intracellularly. However, because their lipid solubility renders them insoluble in blood, these hormones are transported in the blood bound to proteins. Furthermore, steroid hormones are not typically preformed and stored for future use within the endocrine gland. Because they are lipid soluble, they could diffuse out of the cells and physiological regulation of their release would not be possible. Finally, steroid hormones are absorbed easily by the gastrointestinal tract and therefore may be administered orally. 

Cholesterol, mostly esterified, is utilized in the buildup of cell biomembranes. Besides, cholesterol is a precursor to biologically important steroid compounds bile acids (in liver), steroid hormones (in adrenal cortex, male and female sexual glands, and placenta), and vitamin D3, or cholecalciferol (in skin). 

The follicular granulosa cells are the major site of synthesis of female steroid sex hormones the oestrogens. P-Oestradiol represents the principal female follicular oestrogen. Oestriol is produced by the placenta of pregnant females. Oestriol and oestrone are also produced in small quantities as products of P-oestradiol metabolism. 

A large number of hormones and drugs which find their abundant usage in a bad way, namely cortisol (17-hydroxycorticosterone or hydrocortisone), insulin, morphine, barbiturates (sedatives), vitamin B12, digoxin and human growth hormones, such as somatotropin (elaborated in the placenta),... 

The production of progesterone and oestrogen is important for the first 9-10 weeks of pregnancy. After this, the placenta and also the adrenal cortex of the foetus gradually take over the production of these hormones. 

The interaction between the adrenal cortex of the foetus and the placenta in production of steroid hormones is complex. In outline, the placenta produces progesterone from cholesterol (which is available from the maternal blood) whereas the foetal adrenal cortex produces corticosteroids and androgens from the progesterone produced in the placenta. The placenta then converts some of these androgens into oestrogens. The interplay between the placenta and the foetal adrenal cortex is acknowledged by the use of the term foeto-placental unit to describe steroido-... 

The male and female gonads, as well as the placenta of pregnant females and, to a lesser extent, the adrenal cortex, produce a range of steroid hormones which regulate the development and maintenance of reproductive and related functions. As such, these steroid sex hormones have found medical application in the treatment of various reproductive dysfunctions. 

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