Final answer:
The interstitial (Leydig) cells in the testes produce the steroid hormone testosterone, which is crucial for male sexual development, the onset of puberty, spermatogenesis, and other secondary sex characteristics.
Step-by-step explanation:
The interstitial cells, also known as Leydig cells, are located between the seminiferous tubules in the testes. These cells are critical for male sexual development and reproductive function as they produce the steroid hormone called testosterone. Testosterone is responsible for the anatomical differentiation of the male sexual organs in embryos, the onset of puberty, and the facilitation of spermatogenesis. Furthermore, it plays a significant role in muscle development, bone growth, the development of secondary sex characteristics, and maintaining libido. While other hormones such as dihydrotestosterone, androstenedione, growth hormone, and progesterone have various roles in the body, testosterone is the specific hormone produced by the Leydig cells in the testes.