Reproductive Medicine and Osteoporosis
Pp. 426-435 (10)
Robert E. Smith
The fertility cycle in women is controlled by a cascade of events, which are
initiated by protein and steroid hormones. These hormones create signals between the
hypothalamus, the pituitary gland and the ovaries. Oral contraceptives contain an estrogenlike
drug, ethinyl estradiol. It is combined with any of a number of progestin derivatives.
Progestin-only pills are available for women who are breast feeding and those who are unable
to tolerate estrogens. There is also an emergency contraceptive to prevent pregnancy after
unprotected intercourse, called Plan B. One form consists of two pills, each containing 0.75
mg of levonorgestrel. Mifepristone is a synthetic steroid that is used for the termination of
pregnancy up to the 49th day of gestation. It has been tested as a morning after pill to prevent
pregnancy when taken within 12 hours of unprotected intercourse. It is also used in
combination with another drug called Gameprost to terminate pregnancies between weeks 13
and 24. In the USA, levonorgestrel is the preferred emergency contraceptive. It can prevent a
pregnancy up to 72 hrs after unprotected sex or contraceptive failure. Oxytocin and
prostaglandin E2 are also available to induce labor by stimulating uterine contractions. Some
women take hormone replacement therapy, in which a low dose of one or more estrogens
(conjugated equine estrogens) and a progestin are given. Another approach is to increase the
consumption of soybeans and foods made from soybeans (such as soy milk).
Progestin, levonorgestrel, mifepristone, gameprost, prostaglandin E2, soy.
Adjunct Assistant Professor Park University and Consultant Science Advisor United States Food and Drug Administration (FDA) USA