The alphafetoprotein is a glycoprotein synthesized in the yolk sac and in fetal liver in the first three months of pregnancy . Its blood level gradually decrease until it disappears completely at 2-3 weeks after birth.
GnRH is produced by placenta, especially in the first part of pregnancy. Its structure is similar to hypothalamic GnRH.
Identical to pituitary , ACTH is produced by cells of the syncytiotrophoblast and decidua at progressively higher concentrations, up to labor. Its production is modulated by placental CRF. The hormone probably acts in a paracrine way by influencing the placental steroidogenesis and intervening in labor.
IGF -I and IGF -II, insulin like growth factors , are growth factors produced by the trophoblast and later by fetus. They are important in the initial invasion of trophoblast and in the growth of the fetus.
The inhibin and activin modulate the growth and proliferation of various tissues; they are produced by the placenta and fetal membranes, reaching a peak at the end of pregnancy and modulate in different ways the endocrine activity of placenta.
Prolactin is an essential hormone for lactation. It is produced by the maternal hypophysis , the myometrium and endometrio. Prolactin rises between the tenth and the twelfth week, under the stimulus of high levels of estrogen. It then slowly decreases until the end of pregnancy. There is also a prolactin, produced by the decidua, equal to those hypophyseal, whose function is to reduce the permeability of amnios fluids and of electrolytes from fetus to mother.
So, we see that steroid hormones control many vital functions in your body. Of course, we wouldn't have these or any steroids if we did not have cholesterol. It could be said that the most important steroid molecule in your body is cholesterol , because cholesterol is the parent compound from which steroids are derived. It is basically the precursor for steroid hormones and other steroids. We see by looking at the structure of cholesterol that it is a steroid, because it has the four rings of carbon atoms. Attached to the rings we see a hydrocarbon tail and a hydroxyl group . Cholesterol is a 27-carbon steroid and has a molecular formula of C27H45OH.
The most commonly used AAS in medicine are testosterone and its various esters (but most commonly testosterone undecanoate , testosterone enanthate , testosterone cypionate , and testosterone propionate ),  nandrolone esters (most commonly nandrolone decanoate and nandrolone phenylpropionate ), stanozolol , and metandienone (methandrostenolone).  Others also available and used commonly but to a lesser extent include methyltestosterone , oxandrolone , mesterolone , and oxymetholone , as well as drostanolone propionate , metenolone (methylandrostenolone), and fluoxymesterone .  Dihydrotestosterone (DHT; androstanolone, stanolone) and its esters are also notable, although they are not widely used in medicine.  Boldenone undecylenate and trenbolone acetate are used in veterinary medicine .