In biology, the gonadosomatic index (GSI) is the calculation of the
gonad mass as a proportion of the total
body mass. It is represented by the formula:[1]
GSI = [gonad weight / total tissue weight] × 100
It is a tool for measuring the
sexual maturity of animals in correlation to
ovary development and
testicle development. The index is frequently used as reporting point in OECD test guideline, which may be used as indication or evidence of potential endocrine disruption effect of chemicals in regulatory framework (EFSA and ECHA, 2017).[2][3]