Daily administration of caffeine (30 or 60 mg/kg) to mature male rabbits for four consecutive weeks caused an increase in the plasma follicle stimulating hormone (FSH) and a decrease in the luteinizing hormone (LH). Testosterone was increased with the higher dose only while adrenocorticotrophic hormone (ACTH) was not altered by either one. These results suggest that the effects of caffeine on the two gonadotrophic hormones, FSH and LH, involve two separate pathways. The light microscope study revealed reduced sizes of the seminiferous tubules, inhibited spermatogenesis, fatty degeneration of the liver and hepatic lesions. The adrenal glands exhibited signs of stimulated steroidogenesis. It is concluded that long term intake of caffeine induces suppression of spermatogenesis mainly through inhibition of FSH release and this effect is maintained even in the presence of normal or high levels of testosterone and LH.

Department of Zoology Faculty of Science University of Qatar Doha