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Sexual differentiation hormones


During embryonic development there is a sexually indifferent stage in which the embryo has the potential Sexual differentiation hormones develop either male or female structures.

Internally, adjacent to each developing gonad, are two primitive ducts that can give rise to either the male or the female reproductive tracts. The Wolffian mesonephric ducts are more medial. Sexual differentiation begins with sexual determinationwhich depends upon the sex chromosomes, X and Y. Sexual determination involves the specification of the gonads as either testes or ovaries.

The protein produced by SRY activates a gene network that directs the gonads to develop as testes. In the absence of a Y chromosome and SRY, the gonads develop as ovaries.

Once the Sexual differentiation hormones begins to develop as a testis, the two support cells in the testis differentiate and begin to generate important regulatory molecules that direct sexual differentiation. The Leydig cells produce testosteronewhich promotes development of the Wolffian ducts. The Wolffian ducts then differentiate to form the epididymis, vas deferens, seminal vesicles, and ejaculatory ducts. Female development proceeds when there is an absence of the SRY gene.

Obstet Gynecol Clin North Am....

No testosterone Sexual differentiation hormones MIS is made. MIS is expressed mainly by small growing follicles. The level of MIS is "Sexual differentiation hormones" a good indicator of the size of the ovarian reserve ability to produce eggs capable of being fertilized.

A test for MIS level may be used in the context of in vitro fertilization treatment, as a means to predict how the woman will respond to controlled ovarian stimulation. Ovarian development occurs in the absence of SRY activity, but it does not occur by "default".

Our understanding of the important signals required for sexual differentiation derives in part from the study of rare individuals who have disorders of sex development. Two disorders that affect genetically XY individuals are particularly instructive: In androgen insensitivity syndromethere is a mutation in the androgen receptor such that the tissues do not respond to testosterone or other androgens.

Note that the following description is that of complete androgen insensitivityin which the androgen receptor is completely defective with no response to androgens.

However, partial androgen insensitivity can also occur.

The gonads that develop in androgen insensitivity syndrome are testes. An individual with complete androgen insensitivity syndrome will develop externally as a female, because the development of the external genitalia penis with penile urethra and scrotum with descended testes depends upon androgen Sexual differentiation hormones. Furthermore, at puberty, breast development occurs because the testosterone produced Sexual differentiation hormones converted to estrogen by other tissues, and this estrogen stimulates breast development.

The syndrome may be initially recognized because the individual has amenorrhea a lack of menstruation. Another aspect of the phenotype is little growth or armpit or pubic hair, which also depends upon androgen signaling.

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