Cypermethrin is an endocrine disruptor (in addition to its neurotoxic and carcinogen effects). More precisely, it is an antagonist of androgen receptors and perhaps also a steroidogenesis inhibitor. By these mechanisms, it causes a decrease of sperm production. It probably affects most vertebrates as these effects were observed in rat and brown trout Salmo trutta.

Liu et al., 2010. Effects of beta-cypermethrin on male rat reproductive system. Environmental Toxicology and Pharmacology 30, 251-256.

Sun et al., 2007. Antiandrogenic activity of pyrethroid pesticides and their metabolite in reporter gene assay. Chemosphere 66, 474-479.

My studies in fish, pertaining to some pesticides also showed structural disruption and degenerative variation in the testes and ovaries, leading to histopathologyical changes. As a result it may leads to decreased sperm and ova production

Insecticides can affect the male reproductive system at one of several sites or at multiple sites. These sites include testes, sex glands, and the central nervous system. Insecticides may directly damage spermatozoa, alter Sertoli cell or Leydig cell function, or disrupt the endocrine function in any stage of hormonal regulation that leads to reduction in sperm count, increase sperm abnormalities and may leads to infertility.

In addition to their role as endocrine disruptor the pyrithroids also inflicts oxidative stress on various tissues (we have huge unpublished data of embryonic disruptions of cypermethrin that were ameliorated on citrus juice treatment). Our recent paper on testicular histopathological changes of fluoride exposure and their ameliorations on jambul pulp extract give an insight to the oxidative stress related changes in testis. Following is the completed reference of the paper which is available free online.

PROTECTIVE ROLE OF JAMBUL (SYZYGIUM CUMINI) FRUIT-PULP

EXTRACT AGAINST FLUORIDE-INDUCED TOXICITY IN MICE

TESTIS: A HISTOPATHOLOGICAL STUDY. Fluoride 45(3 Pt 2)281–289 (2012)

Pyrethroid insecticides and their metabolites can disrupt the endocrine balance as well as exert an oxidative stress. In addition, synthetic pyrethroid insecticides induce

histopathological alterations in different mammalian organs, including the testes. My studies on lambda-cyhalothrin showed a reduction in epididymal sperm count and histopathological changes in mice testes.