Researchers at the University of Oulu have discovered a previously unknown mechanism by which certain drugs and environmental chemicals can influence the balance of sex hormones. The focus is on the Pregnan-X receptor (PXR), which is considered a sensor for chemical stress and regulates the liver during the processing of drugs. The study shows that PXR also controls the production of sex hormone-binding globulin (SHBG) – a protein that transports testosterone and estrogen in the blood and determines their free, biologically active amount.

In the study, healthy volunteers were given the antibiotic rifampicin, one of the strongest known PXR activators, for one week. In almost all participants, the SHBG levels in the blood doubled; in men, the total testosterone level also increased. Cell experiments confirmed that rifampicin boosts SHBG production in liver cells – an effect that did not occur when PXR was blocked.

The researchers see this as a new indirect way in which chemicals can change the availability of sex hormones. PXR is activated by a wide range of substances – including certain drugs, nutritional components and environmental chemicals such as pesticides, flame retardants and plastic additives. The discovery could explain why such substances disrupt the endocrine system.

According to the scientists, the results open up new possibilities to predict the hormonal effects of drugs and environmental pollution and to develop safer substances. They also underline the importance of PXR as a central regulator in the human hormone balance.

The study was published in the journal Basic & Clinical Pharmacology & Toxicology on March 11, 2026.

Editor: X-Press Journalistenbüro GbR

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