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SEMINAR 1 :  CONTRACEPTION / SEXUAL DIFFERENTIATION
A1.   A2.  A3.  A4.  A5.  B1.  B2.  B3.  B4.  B5. 

Contraception : Progestin component

The progestins are synthetic derivatives of the 19 nortestosterone structure (19 norprogestins). An ethinyl group added at position 17 to testosterone results in an orally active substance. With the 19 carbon removed norethindrone, (19-nortestosterone) is formed, which is a potent progestin.


Norethindrone
Click here for larger view.
Norethindrone. Progestogens, Progesterone antagonists, progesterone, and androgens: synthesis, classification and Uses.
Credits: Clinical Obstetrics and Gynecology, 1995; 38: 813-20.

Other progestins that are presently available in birth control pills also contain the 17 ethinyl group to be orally active.

This same slide also represents some of the other 19 nor-progestins available in birth control pills.


While not synthetically correct, the minimal structural differences from norethindrone is instructive. Many of the newer progestins are actually metabolized to norethindrone.



Acetoxyprogestins

The structure of Acetoxyprogestins The structures of acetoxy progestins(pregnane steroids). Progestogens, Progesterone antagonists, progesterone, and androgens: synthesis, classification and Uses.
Credits: Clinical Obstetrics and Gynecology, 1995; 38: 813-20.

The acetoxy-progestins pictured here while not in combination oral contraceptives are the progestins found in the progestin-only contraceptive intramuscular medroxyprogesterone acetate (Depo Provera). When medroxyprogesterone acetate is given in high enough doses orally, it also effectively suppresses ovulation and has other contraceptive actions found in all progestins (thickens cervical mucous, alters tubal motility, creates an unfavorable endometrium). Therefore, orally active progestins which have contraceptive actions include the 19 nortestosterone derivatives (19 carbon atoms) and the 17 acetoxy-progestin derivatives (21 carbon atoms).


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