The Hormones and Development of One\'s Sex


The objectives of this article as I saw them were, (1) to show how fetal gonads
acquire the ability to function as endocrine organs, and (2), to show the
mechanisms by which the endocrine secretions modulate male development. The
researchers went through an extremely extensive explanation of the formation of
the sexual phenotypes by detailing the development of germ cells. They
explained how women\'s and men\'s gonads appear identical until Leydig cells,
which synthesize testosterone, appear in the connective tissue. This is when
differentiation begins.

The mechanism that this differentiation occurs is as follows. There are two
duct systems which are basically sex specific. In men, Wolffian ducts are
dominant and Mullerian ducts are regressive. Whereas in women it is just the
opposite. Jost believed that the fetal testis secret a hormone which causes such
a differentiation. In order to confirm this belief, he removed the gonads from
embryos, prior to the onset of phenotypic differentiation. All resulted in
female phenotypes. The male phenotype is induced and will not manifest if the
proper secretions are not made from the testis.

Although the article fails to mention how, "Jost deduced that two secretions
from the fetal testis are essential for male development - Mullerian-inhibiting
substance and androgen." The mechanism in which spermatogenic tubules form
Mullerian-inhibiting substance is still unclear to scientists. Problems with
improper levels of this hormone result in genetic and phenotypic reproductive
disorders.

The other hormone secreted by the testis is testosterone. It has two functions;
it promotes maturation of the spermatogenic tubules (and is therefore indirectly
effecting the levels of Mullerian-inhibiting substance), and it has its well
known essential role in the development of the male genital tract.

Throughout this article there were several areas where it seemed to me, issues
were unresolved, however seemed to me that we have the technology to resolve
them. For instance "The Character of the acceptor sites within the nucleus
(that is, whether protein or DNA) and their number are not resolved." Couldn\'t
one do a radioactive trace or a non-vital stain of some sort to distinguish the
protein from the DNA.

The development of one\'s sex is therefore far more than just a genetic decision,
it is (once again) a complex cascade of hormones acting on receptors. These
receptors go on to activate effector molecules which activate target molecules.
If at any point this system is disrupted in any way, one either has the
underdevelopment or incorrect development of the phenotypical gonadal
characteristics.

Category: Science