Women who are breastfeeding have elevated prolactin levels. The main purpose of the hormone prolactin is to prepare the female body for a new baby by producing milk and prevent ovulation. This has given prolactin the nick name milk hormone. Prolactin levels increase up to 10 times during pregnancy.

Pituitary tumors

Hyperprolactinemia is often caused by a prolactinoma.The pituitary gland produces different hormones. A tumor on the pituitary gland can cause an overproduction of any of these hormones. Hyperprolactinaemia is caused by a tumor producing prolactin. What causes this tumor to appear is unknown. My own theory is that it might be the other way around – Hyperprolactinemia causes the area in the pituitary gland, where it’s produced, to grow. This meaning that the problem is not a tumor but a hormonal imbalance (possibly caused by malnutrition).


Some medication can stimulate prolactin production, such as some antidepressants, blood pressure medicine and anabolic steroids.

Other or unspecified reasons

  • Stress
  • Some diseases e.g. thyroid or liver disease
  • Head injury
  • No reason can be identified (idiopathic hyperprolactinemia)

The human body is complicated and far from fully understood. It is very likely that Hyperprolactinemia might cause other complications. I would even claim that it’s unlikely for hormonal imbalances to be isolated and not affect other bodily functions. Hyperprolactinemia is linked to e.g. both the digestive and immune system.