Mullerian inhibiting substance: a fetal hormone with surgical implications.

Mullerian Inhibiting Substance (MIS) is secreted from the fetal (and postnatal) testis and is known to cause regression of the Mullerian ducts, the anlage of the fallopian tubes, uterus and upper vagina. It is a large glycoprotein hormone, the action of which appears to be modulated by sex steroids: mainly testosterone in mammals and oestrogen in birds. Recent evidence has raised the possibility that its action may be to diminish cell surface phosphorylation and thereby change the direction of differentiation of the Mullerian duct towards regression. Other suspected functions for MIS include control of testicular descent and inhibition of malignant tumours of the female genital tract.