Introduction to Male Reproductive Endocrinology

00:01 We're going to go through one more hypothalamic pituitary gonadal axis.

00:06 This particular one is going to be hypothalamic pituitary testis axis.

00:11 The preoptic nucleus is the main nucleus responsible for GnRH secretion with possible minimal assistance from the supraoptic nucleus.

00:20 So this is the same as the other gonadal axis with the ovaries.

00:24 It's going to stimulate once again the gonadotropes in the anterior pituitary, so the preoptic nucleus will release most of the releasing hormone, gonadotropin releasing hormone, to the gonadotropes to stimulate the release of luteinizing hormone and follicle stimulating hormone.

00:40 The actions of luteinizing hormone and follicle stimulating hormone.

00:46 The luteinizing hormone primarily regulates the Leydig cell; the follicle stimulating hormone primarily, the Sertoli cell.

00:55 So what do these two different cells do? Well, Sertoli cells are gonna be involved in spermatogenesis, regulation of growth factors, and other regulatory proteins, but it's the Leydig cells that make the testosterone.

01:09 So, luteinizing hormone starts off the process, activates side-cleaving enzyme to have cholesterol drop down in the various steroid genesis process to make testosterone.

01:25 So all the testosterone is going to be occurring here in the Leydig cell.

01:30 As it's passed over to the Sertoli cells, some of it comes out and the one part that comes out will then be translated in the circulation to the various cells of the body.

01:42 So what does the Sertoli cell do with the testosterone that it gets? It's gonna release a little bit of it into help with sperm being developed and maturing.

01:54 The other portion that happens is there is aromatase located in Sertoli cells and Sertoli cells will use that aromatase to convert testosterone to estradiol.

02:08 And interestingly, it's estradiol that helps produce more testosterone.

02:14 So although you like to think of having males primarily producing testosterone and females primarily producing estradiol, it doesn't work like that.

02:23 We both make both hormones, it's just the concentration in the blood is different between the various sexes.