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Genetic Link Between Weight Gain and Contraceptive Implant

WEIGHT gain while using contraceptives is varying, but variants in the oestrogen receptor 1 gene (ESR1) may help to identify women at risk of significant weight gain. Variants in the ESR1 gene have been associated with increased weight gain when using a progestin-containing implanted contraceptive.

A study published out of the University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA revealed an association between an etonogestrel contraceptive implant, weight gain, and ESR1 gene variation. The study used the medical records of 276 women with diverse ethnicities to determine the degree of weight gain post-implantation and undertook pharmacogenomic studies to assess for a possible genetic component related to the pattern of weight gain.

73.9% of the women studied gained weight post-implantation, with a median increase of 3.2 kg over an average of 27 months. The women with a homozygous ESR1 rs9340799 variant gained, on average, 14.1 kg more weight than other women in the study. This variation is associated with upregulation of ESR1. The ESR1 gene has previously been identified to play a role in the effects of several medications but has not been associated with obesity or metabolic syndrome.

The ESR1 gene is located on chromosome six and encodes an oestrogen receptor that, when activated, contributes to hormone binding within cells and DNA transcription. The contraceptive studied is a rod-like implant that releases an etonogestrel progestin to inhibit ovulation and act as one of the most reliable forms of contraception. Other contraceptives may also have genetic factors contributing to patterns of weight gain, which needs further study. Aaron Lazorwitz, Assistant Professor of Obstetrics/Gynaecology and Family Planning at the University of Colorado School of Medicine and lead author of the study, highlighted this: “It is imperative to better understand how individual genetic variation may influence a woman’s risk of adverse weight gain while using exogenous steroid hormone medications.”

In the context of the rise of personalised and precision medicine, identifying genetic components to help tailor the best care for patients is an important field of study. Prof Lazorwitz outlined the value of genetic considerations in clinical care: “As our understanding of pharmacogenomics in women’s health expands, we can develop individualised counselling that may reduce the incidence of hormone-related adverse effects, improve patient satisfaction, and help prevent future health risks associated with weight gain.”