The Leydig intermediate cells are located between the seminiferous tubules of the testes and produce the male sex hormone testosterone. Thus, they are responsible for the secondary sexual characteristics of the male and the maintenance of all sexual functions.
What are the Leydig intermediate cells?
Leydig intermediate cells were named after their discoverer, Franz von Leydig. They are located in the intercellular spaces (interstitium) of the testes and account for about 10 to 20 percent of the testicular mass. Their function is to produce the sex hormone testosterone. Testosterone production has two peaks. For example, the intermediate Leydig cells are stimulated to produce testosterone by stimulation with the pregnancy hormone chorionic gonadotropin starting at the eighth week of pregnancy. In the process, the male sexual characteristics are formed. After their differentiation, testosterone is initially no longer produced from the sixth month of pregnancy. The second phase of hormone production begins with puberty. To identify testicular tissue, the so-called Leydig cell stimulation test is performed. In this test, human chorionic gonadotropin is added to the tissue to be tested. If Leydig intermediate cells are present, testosterone is produced, which can then be detected.
Anatomy and structure
As mentioned earlier, intermediate Leydig cells are the most important type of cells in the testis. They are found between the tubules of the testis in the interstitium and represent large, acidophilic cells. Their nucleus is bright and roundish. There are many mitochondria in their cells. They are arranged in groups between the seminiferous tubules of the testis. Usually they are located near the capillaries. The cells are also characterized by the presence of lipid droplets and much endoplasmic reticulum. This indicates the production of steroid hormones. In addition to testosterone, dihydrotestosterone (DHT), dihydroepiandrosterone (DHEA) and estradiol are also produced there. So-called Reincke crystals of crystalline protein deposits sometimes occur in the cytoplasm. The significance of the Reincke crystals has not yet been clarified. However, they seem to be waste products. Sperm production stimulated by testosterone takes place in the testicular ducts. They are protected by Sertoli cells and separated by testicular connective tissue, in which the intermediate Leydig cells are located.
Function and tasks
The most important function of the intermediate Leydig cells is to produce testosterone along with a small amount of other sex hormones. The initial substance for hormone synthesis is cholesterol. Via the blood, testosterone reaches the sex organs, skin and prostate. There it is converted into dihydrotestosterone. In the fatty tissue and liver, the female sex hormone estradiol is produced from testosterone. This is why overweight men often become feminized to a certain extent, and their breasts may also enlarge. Testosterone primarily determines the development and function of the male sex organs and the maturation of sperm. Furthermore, it promotes growth, influences the physique, the type of hair, the activity of the sebaceous glands or the size of the larynx. During puberty, therefore, male adolescents often develop acne due to increased sebum production. Normal male sex drive and potency are dependent on testosterone. It is also responsible for increased blood formation and muscle building. Therefore, it is often misused as a doping agent. Last but not least, testosterone often produces a certain aggressiveness, which is considered a male trait. The production of testosterone in the Leydig intermediate cells is controlled by the hypothalamus and the pituitary gland. When there is a higher demand for testosterone, the hypothalamus produces the hormone gonadotropin-releasing hormone (GnRH). This hormone in turn stimulates the pituitary gland, specifically the anterior pituitary, to produce the regulatory hormones FSH (follicle-stimulating hormone) and LH (luteinizing hormone). LH then stimulates the intermediate Leydig cells to produce testosterone. In interaction with FSH, testosterone now promotes sperm development and maturation. As part of a negative feedback loop, the production of GnRH, FSH and LH is stopped when sufficient testosterone is present. This feedback is reported to the hypothalamus and pituitary gland by the substance inhibin produced in the Sertoli cells.The intermediate Leydig cells then reduce testosterone production again.
Diseases
The Leydig intermediate cells may experience disturbances in the production of testosterone. In most cases, this is underproduction. This reduced testosterone production is called hypogonadism. A distinction must be made between primary and secondary hypogonadism. In primary hypogonadism, the intermediate Leydig cells are unable to produce sufficient testosterone, or any testosterone at all, due to pathological changes or even their absence. The testes can be damaged by various influences, such as inflammation, tumors, accidents, radiation, surgery or medication. Sometimes they are even missing from birth. For example, an infection with mumps can destroy the testicles so that hormone production is no longer possible. Sometimes a genetic disorder, such as Klinefelter syndrome, also leads to hypogonadism. In Klinefelter syndrome, there is one too many X chromosomes. Secondary hypogonadism is caused by disorders in the hypothalamus or pituitary gland. If the production of the hormones LH, FSH or GnRH is disturbed, the Leydig intermediate cells can also no longer be sufficiently stimulated to synthesize testosterone. The symptoms of testosterone deficiency depend on the age at which the hypogonadism occurs. If it already exists in childhood or adolescence, the development of male sexual characteristics is very delayed or does not occur at all. If the testosterone deficiency does not develop until later in life, very unspecific symptoms occur in addition to impotence. Since the efficiency of the Leydig intermediate cells decreases in the course of life, hypogonadism is typical in older age.
Typical and common testicular disorders
- Testicular cancer
- Undescended testis (maldescensus testis)
- Testicular pain
- Epididymitis
