Pesticide- and sex steroid analogue-induced endocrine disruption differentially targets hypothalamo-hypophyseal-gonadal system during gametogenesis in teleosts - A review

- Endosulfan mimics estrogenic action to differentially affect gonads in teleosts.
- Endosulfan modulates brain-pituitary axis to target gonads.
- Malathion affects brain-pituitary axis to impart gonadal dysfunction.
- Pesticide-induced endocrine disruption alters hypothalamo-hypophyseal-gonadal axis.

Pesticide-induced endocrine disruption often mimics sex steroidal action resulting in physiological functional disarray of hypothalamo-hypophyseal-gonadal (HHG) system at multiple levels. Among various group of pesticides, organochlorine and organophosphate family of pesticides are known to impart sex steroidal mimicking activity with slightly higher resemblance to estrogens when compared to androgenic action. This review will highlight the effects of organochlorine (for e.g. endosulfan) and organophosphate (for e.g. malathion) pesticides in comparison with sex-steroid analogue-induced changes on HHG axis during gametogenesis in few teleost fish models. Interestingly, the effects of these compounds have produced differential effects in juveniles and adults which also vary based on exposure dosage and duration. Further, the treatments had caused at times sexually dimorphic effects indicating that the action of these compounds bring out serious implications in sexual development. A comprehensive overview has been provided by considering all these aspects to recognize the adverse impacts of pesticide-induced endocrine disruption with special reference to endosulfan and malathion as those had been applied even today or used before for controlling agricultural pests in several Asian countries including India. This review also compares the effects of sex-steroid analogues where in sex reversal to reproductive dysfunction is evident, which may imply the extent of sexual plasticity in teleosts compared to other vertebrates.