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  • Title: Mode of action of IUDs.
    Journal: IPPF Med Bull; 1975 Jun; 9(3):3-4. PubMed ID: 12307554.
    Abstract:
    A summary of views presented at the International Planned Parenthood Federation Biological Workshop, 1975, on the mode of action of intrauterine devices (IUD) and ovum implantation is presented. Blastokinin, a recently discovered protein, prepared the uterus for implantation. The uterus is considered to be the major site of action of the IUD in humans and the rhesus monkey. The IUD seems to interfere with implantation by affecting either the blastocyst or endometrium, or both. Increased prostaglandins (PG) have been found in the endometrium and uterine luminal fluid in direct association with the presence of an IUD. Leukotaxis or uterine hypertrophy can be reduced or abolished by agents that inhibit PG synthesis. The addition of copper or progesterone to IUDs enhances their contraceptive effect. This increased contraceptive effectiveness could be due to 1) an effect on sperm that inhibits fertilization, 2) the destruction of the blastocyst before implantation, 3) an endometrium made hostile to the implanting ovum, or 4) an early abortifacient action mediated through increased uterine contractility or an effect on the corpus luteum. In vitro human experiments with copper show an inhibition of sperm motility, whereas in vivo tests had contradictory results. The copper causes considerable changes in trace element composition and tissue enzyme activity in the human endometrium. Progesterone-bearing IUDs seem to exert their effect through major morphological and metabolic changes in the uterus.
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