Who won't be helped by contraceptives

Alexey Timoshenko, "The Attic"

In women with a certain mutation in one of the genes, hormonal contraceptives may not work effectively enough. According to a study by American gynecologists, in 5% of women, progestin, the active hormone of such drugs, is broken down faster than usual. As a result, the effectiveness of contraceptives is reduced.

Hormonal contraceptives are made on the basis of progestins – synthetic analogues of progestogen, and often estrogen, one of the female sex hormones, is added to them. Progestogens act due to a variety of effects at once – from blocking ovulation to changes in the uterus and fallopian tubes, so they are included in hormonal pills for constant intake, and in pills for emergency contraception. Hormonal implants that release a small amount of hormones from a capsule sewn into the forearm are also made on the basis of progestins – we can say that in practice "progestins" and "hormonal contraception" often represent the same thing.

For their study (Lazorwitz et al., Influence of Genetic Variants on Steady-State Etonogestrel Concentrations Among Contraceptive Implant Users), doctors from the University of Colorado recruited 350 healthy women with an implanted implant based on one of the progestins, etonogestrel. Scientists took blood samples from all participants to determine the level of this hormone. In addition, scientists have analyzed their genotype. This allowed us to determine that as a result of increased activity of one of the genes, CYP3A7, the concentration of synthetic hormone decreases and, consequently, the effectiveness of hormonal contraception should decrease.

However, scientists did not measure the Pearl index, that is, the frequency of unwanted pregnancies when using a certain contraceptive. There were 18 women who showed increased CYP3A7 activity, which is too small for statistically reliable results. However, the authors point out that the effect they recorded may have clinical significance.

"When a woman says that she got pregnant while using contraception, we often believe that this is somehow due to her negligence," the university's press service quotes the words of the study's lead author Aaron Lazorwitz. "However, these new findings indicate that we should listen to the patients and take into account that something in their genes may be the cause."

The CYP3A7 gene is responsible for protein synthesis from the family of cytochromes, chemically active molecules. Many of the cytochromes play a key role both in normal metabolism and in detoxification. Specifically, CYP3A7 can process progestins, among other things. Usually, the researchers write, this protein is synthesized only during intrauterine development, but a certain variant of this gene (an allele, as geneticists say) leads to the fact that CYP3A7 remains active in adulthood.

The new discovery, according to the authors, will allow for more effective selection of contraceptives and other drugs. Progestins are prescribed in a number of other cases – from hormone therapy during menopause to the treatment of a number of malignant tumors, and the analysis of the genotype of patients is becoming more and more accessible every year. Perhaps in the foreseeable future, contraception and therapy will be selected after a relatively simple test.

Portal "Eternal youth" http://vechnayamolodost.ru