Influence of hyperprolactinaemia due to metoclopramide on gonadal function in men

Five clinically normal male volunteers were given metoclopramide, 10 mg t.d.s. for 6 weeks. During treatment prolactin concentrations were elevated (over 50 ng/ml) in all. LH, FSH, testosterone and cortisol concentrations were not altered. No change was observed in LH or FSH responses to LHRH testing 4 weeks after the beginning of therapy, compared with pre-treatment values. A reduction in seminal volume and total sperm count were observed in each subject. Four noticed a decrease in libido and three lost spontaneous erections. While the metoclopramide-induced hyperprolactinaemia could be the cause of the observed changes in semen and erectile activity, it is possible that this dopamine receptor blocking drug might directly affect central or peripheral mechanism of erection, the testes or accessory organs.