Low prolactin (hypoprolactinemia) is a condition where the pituitary gland in the brain produces less prolactin hormone than normal. Prolactin levels measured below 15-25 µg/L in women and 5-10 µg/L in men are generally considered low. This condition is usually caused by damage to the pituitary gland, which secretes prolactin hormone. Additionally, certain health problems and the use of specific medications can also lead to low prolactin.