21.1 Genetic factors and hormones that determine gender

Hormonal factors: introduction

Since 1950 (work of A. Jost [2]) one knows that the development of the phenotypic gender as opposed to the genotypic gender primarily depends on hormonal factors. A. Jost has shown that the castration of male genotype embryos (XY) leads to a feminine phenotype.

During the embryonic period (from the 6th week) the interstitial cells (Leydig) in the fetal testes secrete the testosterone hormone that is responsible for the male differentiation of the genital anlagen. Roughly, from the 7th week the antimüllerian hormone (AMH), which belongs to the TGF-b (transforming growth factor b) family and is produced by the supporting cells (Sertoli) (3), leads to an atrophy of the paramesonephric duct (Müller).

In contrast, the female sexual apparatus differentiates itself spontaneously in the direction of the feminine phenotype without particular hormonal influences.


Schematic diagram of the hormonal and genetic factors involved in the development of the male phenotype.

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