Female tadpoles that swim in water containing a specific progestogen, levonorgestrel (LNG), have been shown to be subject to abnormal ovarian and oviduct development, resulting in adult sterility, report Cecilia Berg and colleagues, Uppsala University, Sweden.

The team investigated the effects of developmental LNG exposure on sex differentiation, reproductive organ development and fertility in the model frog Xenopus tropicalis. Tadpoles were exposed to 0, 0.06 or 0.5 nM LNG via the water from hatching until metamorphosis. Exposure was seen to severely impair oviduct and ovary development and all adult females exposed to the highest concentration of LNG completely lacked oviducts. The fertility of male frogs was unaffected.

Progestogens are hormones used in contraceptives, cancer treatment, and hormone replacement therapy. They are released into the environment via sewage systems.

• Early life progestin exposure causes arrested oocyte development, oviductal agenesis and sterility in adult Xenopus tropicalis frogs
  M. Kvarnryd, R. Grabic, I. Brandt, C. Berg,
  Aquatic Toxicology 2011.
  DOI: 10.1016/j.aquatox.2011.02.003