Reports of reduced prostate and seminal vesicle weights, as well as altered testicular function, have been partially explained by the effect of marijuana in lowering serum testosterone needed for proper function and support.

Chronic exposure of laboratory animals, such as rats, mice, and monkeys to marijuana and to the various cannabinoids in marijuana has altered the function of several of the accessory reproductive organs. THC appears to depress prolactin, thyroid gland function, and growth hormone while elevating adrenal cortical steroids. Other hormones that might have a synergistic or antagonistic effect upon reproduction in the male are the adrenal cortical hormones, prolactin, thyroid hormones, and growth hormones. The THC-induced block of GnRH release results in lowered LH and FSH which is responsible for reduced testosterone production by the Leydig cells of the testis. Both gonadotropins appear to respond to a single releasing factor from the hypothalamus, GnRH, which is sensitive to catecholamine neurotransmitters. The two gonadotropins, LH and FSH, secreted by the pituitary gland are of major importance to reproduction in the male. The dopaminergic and serotonergic fibers seem to be particularly important. It is probable that THC affects these hormones through its ability to alter various neural transmitters in the hypothalamus or neural transmitters in the CNS which impinge on the hypothalamus. Marijuana affects a variety of hormones that are regulated by hypothalamic function and it appears that the psychoactive ingredient, THC, is the major compound responsible for this action.

Cortical hormones