SEXUAL-DIFFERENTIATION AND ENVIRONMENTAL ENDOCRINE DISRUPTERS

Male sexual differentiation is dependent on normal testicular function , including secretion of testosterone from the Leydig cells, and mulle rian-inhibiting substance from the Sertoli cells. External factors, su ch as anti-androgens and oestrogens, that disturb endocrine balance ca use demasculinizing and feminizing effects in the developing male fetu s. Oestrogens also causes adverse effects in female fetuses, whereas a nti-androgens have Little influence. A growing number of chemicals hav e been found to possess either weak oestrogenic, anti-androgenic or ot her hormonal activities, and these are often referred to as endocrine disrupters. In animals in the wild, abnormal sexual development has be en associated with exposure to mixtures of endocrine disrupters. The e merging adverse trends in human reproductive health, such as increased incidences of cryptorchidism, hypospadias and testicular cancer, and the ubiquitous presence of endocrine disrupters in the environment, su pport the hypothesis that disturbed sexual differentiation could in so me cases be caused by increased exposure to environmental endocrine di srupters.