Hyperprolactinaemia causes hypogonadism by several mechanisms: high prolactin (PRL) levels lead to partial suppression of GnRH release, as well as loss of its pulsatility; prolactin also interferes with the action of LH and FSH on the gonad, causes an increase in adrenal androgen secretion, and leads to inhibition of positive oestrogen feedback on GnRH and LH secretion in women.