Leydig cells (or Testicular interstitial cells) are the main producers of the male sex hormone testosterone. They are located near the seminiferous tubules of the testes, where they secrete testosterone in the presence of luteinizing hormone (LH). Testosterone is the driving force behind male sexual development and fertility and is critical to spermatogenesis, male embryonic development, and the development of primary and secondary sexual characteristics.

Leydig cells produce testosterone in the male testicles
Leydig cells produce testosterone in the male testicles

What is a Leydig cell?

A Leydig cell is a type of specialized cell found in the male testicle. Leydig cells are located in the connective tissue of the seminiferous tubules, where they produce the androgen Testosterone. Testosterone production by Leydig cells is controlled by the presence or absence of luteinizing hormone (LH).

Functions of Leydig cells

The key function of a Leydig cell is to produce the male sex hormone testosterone. Testosterone is vital for Spermatogenesis (i.e. sperm production) and for the development of primary and secondary male sexual characteristics.

Leydig cells produce testosterone in male organisms
Leydig cells produce the male sex hormone: testosterone

Testosterone production

Leydig cells produce testosterone in the male testicles. This process is controlled by the luteinizing hormone (LH) secreted by the pituitary gland in legumes. In the presence of LH, the Leydig cells are stimulated to produce testosterone.

Testosterone production is controlled by a negative feedback loop between testosterone and LH. When testosterone levels are high, LH is suppressed and production stops. When testosterone levels are low, LH is released from the pituitary gland and production resumes. Therefore, testosterone and LH are produced and secreted in alternating pulses.


Male sex cells (i.e. sperm) develop from germ cells in the testes through a process called Spermatogenesis. Sperm production is driven by testosterone, so the Leydig cells, as the main producers of this hormone, play a crucial role in spermatogenesis.

Testosterone is needed for spermatogenesis
Testosterone is important for healthy sperm production

Testosterone, secreted by Leydig cells, diffuses into the seminiferous tubules of the testes, where spermatogenesis takes place. The seminiferous tubules consist of three main cell types; these are the peritubular myoid cells (PTM), the Sertoli cells and the germ cells.

Germ cells are a type of unipotent stem cell that divide to produce gametes in sexually reproducing organisms. In male organisms they form sperm cells. During spermatogenesis, germ cells divide by meiosis to produce four haploid daughter cells. Each daughter cell is a genetically unique sperm cell and can take part in fertilization.

Testosterone is an important part in this process as it helps complete meiosis, sperm maturation, and sperm release. In the absence of testosterone, germ cells can still divide by meiosis. However, the resulting sperm do not mature or cannot be released, resulting in infertility.

Male Embryo Development

Male embryonic development is driven by testosterone
Testosterone drives the development of the male genitals in the embryo

The testosterone produced by the Leydig cells is also crucial for male sexual development, as this hormone is responsible for gender differentiation and the creation of male sexual characteristics.

During the first 6 weeks of development, male and female embryos cannot be distinguished from one another. When the testes of male embryos begin to develop (which happens around week 7), fetal Leydig cells migrate into the developing gonads and testosterone production begins. Testosterone is critical to the formation of the male genitals and the descent of the testicles during the last 2 months of fetal development.

Primary and Secondary Sexual Development

Sexual development in men is controlled by testosterone
Testosterone controls the development of primary and secondary sexual characteristics

After birth, testosterone is the driving force of primary sexual development, which typically occurs between the ages of 11 and 15 years. During this phase, testosterone induces spermatogenesis, enlargement of the genitals, descent of the testicles and an increase in libido.

Testosterone is also responsible for the development of secondary male sexual characteristics, which include the growth of facial and chest hair and the deepening of the voice. Testosterone is also responsible for the growth spurts of male organisms during puberty.

Structure of Leydig cells

Leydig cells are characterized by a large nucleus and abundant lipids
A Leydig cell has a large, round core

Leydig cells are typically found in groups of ten in the connective tissue of the vas deferens. They are characterized by their large, round cores, their prominent nucleoli and their high lipid content.

Leydig cells also contain abundant smooth endoplasmic reticulum and mitochondria, which makes them well suited for steroid (testosterone) production.


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