Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules

Seminiferous tubules

Seminiferous tubules are located in the testes, and are the specific location of meiosis, and the subsequent creation of gametes, namely spermatozoa....

 in the testicle. They produce testosterone

Testosterone

Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...

 in the presence of luteinizing hormone

Luteinizing hormone

Luteinizing hormone is a hormone produced by the anterior pituitary gland. In females, an acute rise of LH called the LH surge triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell-stimulating hormone , it stimulates Leydig cell...

 (LH). Leydig cells are polyhedral in shape, display a large prominent nucleus

Cell nucleus

In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...

, an eosinophilic

Eosinophilic

Eosinophilic refers to the staining of certain tissues, cells, or organelles after they have been washed with eosin, a dye.Eosin is an acidic dye; thus, the structure being stained is basic....

 cytoplasm

Cytoplasm

The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...

 and numerous lipid-filled vesicles.
Leydig cells are named after the German anatomist Franz Leydig

Franz Leydig

Franz von Leydig , also Franz Leydig, was a German zoologist and comparative anatomist.- Life :Franz Leydig was born on May 21, 1821, in Rothenburg ob der Tauber . He was the only boy of three children born to Melchior Leydig, a Catholic and a minor public official, and Margareta, a Protestant...

, who discovered them in 1850.
Leydig cells release a class of hormones called androgens (19-carbon steroid

Steroid

A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...

s).