Background: Heroin is a simple derivative of morphine that is the most used drug in Iran among opioids. Its harmful effects on body organs have been studied. Considering the important effects on the genital system and fertility, studying the effects of heroin on testes seems to be necessary.     

Methods: In this study a total of 30 male mice (Balb/c) were selected and divided into 5 groups of control (Intact, sham I, sham II), experimental I and experimental II. After addiction of the experimental groups to heroin via intra peritoneal injection, the histological structures of testes were studied microscopically.

Results: Histological study of heroin on testes showed that the thickness of the basement membrane of the germinal epithelium and reduction in cell accumulation around some of the seminiferous tubules. Irregularity in spermatogonia, spermatocyte and spermatid, increased distance and degeneration in seminiferous tubules were observed. Increasing connective tissue between seminiferous tubules, decreased number of leydig cells, with a hypochromatic cytoplasm and reduction in their secretory granules, and congestion of testical tissue were also observed.

Conclusion: The results of this study show that heroin used in Iran can result in changes in the structure of testes. Consequently using heroin can influence the reproductive system.