Leydig cells

Examples of Leydig cells in the following topics:

• Hormonal Regulation of the Male Reproductive System

  • However, it is known that initiation of spermatogenesis occurs at puberty due to the interaction of the hypothalamus, pituitary gland, and Leydig cells.
  • The Leydig cells are also capable of producing estradiol in addition to their main product, testosterone.
  • In the testes, LH binds to receptors on Leydig cells, which stimulates the synthesis and secretion of testosterone.
  • Testosterone is made in the interstitial cells of the testes.
  • Inhibin is secreted by the Sertoli cells and acts to decrease the levels of FSH.

• Testicular Cancer

  • Although testicular cancer can be derived from any cell type found in the testicles, more than 95% of testicular cancers are germ cell tumors .
  • Most of the remaining 5% are sex cord-gonadal stromal tumors derived from Leydig cells or Sertoli cells.
  • Most testicular germ cell tumors have too many chromosomes, and most often they are triploid to tetraploid.
  • About half of germ cell tumors of the testis are seminomas.

• Male Hormones

  • FSH enters the testes, stimulating the Sertoli cells, which help to nourish the sperm cells that the testes produce, to begin facilitating spermatogenesis.
  • LH also enters the testes, stimulating the interstitial cells, called Leydig cells, to make and release testosterone into the testes and the blood.
  • The Sertoli cells produce the hormone inhibin, which is released into the blood when the sperm count is too high.
  • If the sperm count reaches 20 million/ml, the Sertoli cells cease the release of inhibin, allowing the sperm count to increase.

• Testes

  • These are lined with a layer of germ cells that develop into sperm cells (also known as spermatozoa or male gametes) from puberty into old age.
  • The developing sperm travels through the seminiferous tubules to the rete testis located in the mediastinum testis, to the efferent ducts, and then to the epididymis where newly-created sperm cells mature.
  • Leydig cells located between seminiferous tubules produce and secrete testosterone and other androgens important for sexual development and puberty, including secondary sexual characteristics such as facial hair and sexual behavior.
  • The sertoli cells are the testes’ somatic cells, necessary for testis development and spermatogenesis.

• Male and Female Gonads

  • Progesterone and estrogen are secreted by granulosal cells, whereas testosterone is produced by thecal cells.
  • Prior to ovulation, follicle-stimulating hormone is secreted by the granulosal cells that convert testosterone into estradiol.
  • Testosterone is secreted by Leydig cells, which are located between the seminiferous tubules.

• Hormonal Regulation of the Reproductive System

  • LH stimulates production of the sex hormones (androgens) by the Leydig cells of the testes.
  • It is also called interstitial-cell-stimulating hormone.
  • In females, FSH stimulates development of egg cells (or ova) in structures called follicles.
  • Follicle cells produce the hormone inhibin, which inhibits FSH production in the female reproductive system.
  • Oxytocin also stimulates the contraction of myoepithelial cells around the milk-producing mammary glands.

• Aging and the Endocrine System

  • This can be attributed to a decrease in IGF-I signaling pathways with advanced cell age.
  • Testosterone is a steroid hormone secreted by the Leydig cells that can act upon many target organs, resulting in development of secondary sexual characteristics and growth spurt at puberty.
  • Estradiol is the female equivalent of testosterone and is secreted from granulosa cells.
  • In vitro, cells treated with testosterone demonstrated a decrease in Ab release.
  • Estrogen acts on the nucleus of the cell by binding with the nuclear endoplasmic reticulum (ER).

• Puberty

  • LH stimulates the Leydig cells of the testes to make testosterone and blood levels begin to rise.
  • For females, as the amplitude of LH pulses increases, the theca cells of the ovaries begin to produce testosterone and smaller amounts of progesterone.
  • Much of the testosterone moves into nearby cells called granulosa cells.
  • Smaller increases of FSH induce an increase in the aromatase activity of these granulosa cells, which converts most of the testosterone to estradiol for secretion into the circulation.

• Male Reproductive Anatomy

  • The walls of the seminiferous tubules are composed of the developing sperm cells, with the least-developed sperm at the periphery of the tubule and the fully-developed sperm in the lumen.
  • The sperm cells are mixed with "nursemaid" cells called Sertoli cells which protect the germ cells and promote their development.
  • Other cells mixed in the wall of the tubules are the interstitial cells of Leydig; these cells produce high levels of testosterone once the male reaches adolescence.
  • Sperm consist of a flagellum (as a tail), a neck that contains the cell's energy-producing mitochondria, and a head that contains the genetic material .
  • When the sperm have developed flagella, or lash-like appendages that protrude from the cell body, and are nearly mature, they leave the testicles and enter the epididymis.

• Cellular Differentiation

  • Three basic categories of cells make up the mammalian body: germ cells, somatic cells, and stem cells.
  • Pluripotent stem cells undergo further specialization into multipotent progenitor cells that then give rise to functional cells.
  • Hematopoietic stem cells (adult stem cells) from the bone marrow that give rise to red blood cells, white blood cells, and platelets
  • Mesenchymal stem cells (adult stem cells) from the bone marrow that give rise to stromal cells, fat cells, and types of bone cells;
  • Epithelial stem cells (progenitor cells) that give rise to the various types of skin cells