- Author: Melanie Dell’Oro
You may know prolactin as the breastfeeding hormone. But somehow that’s not the end of the story, is it? For example, did you know that if you’re struggling to conceive, you should definitely check your prolactin levels? And that we might once again have a lifestyle issue—in other words, a stress problem? We’ll discuss all of this, along with a few more little-known facts about prolactin, in this article.
Prolactin - A Fact Sheet
Prolactin is an effector hormone secreted by the pituitary gland when the hypothalamus signals it to do so. Its direct target organ is the mammary gland (too much technical jargon? Read all about the hormone system here).
Simply put, prolactin has two main effects:
- At the end of pregnancy, prolactin helps develop the mammary gland tissue and enables breastfeeding.
- During breastfeeding, prolactin stimulates milk production and the synthesis of milk components.
Prolactin is also involved in preventing further fertilization during pregnancy. It is also largely responsible for so-called “lactational amenorrhoea,” which is the perfectly natural infertility experienced during the first few months of breastfeeding.
Fun fact: this temporary infertility does not occur in short-lived animals such as mice. This is probably to ensure that they reproduce sufficiently during their short lifespan.
Even in non-pregnant people, tiny amounts of prolactin circulate in the bloodstream. This is normally regulated by dopamine and has no negative effects. Normally. You can probably guess what’s coming next...
Prolactin and infertility
The interesting thing about prolactin is that no corresponding releasing hormone has yet been found, and prolactin reacts to a wide range of stimuli with a rapid, short-term increase. This includes, for example, stress. While this can be perfectly useful for preventing pregnancy in unfavorable metabolic conditions, it can become a real problem when trying to conceive in today’s world. This affects both the person who may become pregnant and the person who may father the child. Chronic stress leads to chronically elevated prolactin levels—and all the fertility-suppressing effects that come with them. Ovulation is prevented, menstruation stops, and male fertility is reduced.
Hypoglycemia and significant weight loss have the same effect and are partly responsible for the absence of menstruation in conditions such as anorexia nervosa.
Sleep disorders also lead to long-term increases in prolactin levels. This is because prolactin is one of the hormones whose secretion is highly dependent on the time of day. The highest amounts are secreted at night while you sleep. If sleep is disrupted—for example by night shifts, jet lag, a shift in sleep patterns, or chronic sleep problems—prolactin levels during the day will be higher than normal.
An underactive thyroid can also prevent pregnancy by affecting prolactin levels or—and this is why close monitoring by a gynecologist is essential during pregnancy if the thyroid is underactive—lead to an unintended miscarriage.
So if you’re struggling to conceive, it’s definitely worth checking the factors mentioned above or having your prolactin levels tested.
A beer for breastfeeding—please don’t!
Beer increases milk production. Many breastfeeding people have probably heard this well-intentioned advice. In fact, it’s not the alcohol that has this effect, but a component of barley. So there’s no need to drink alcoholic beer. On the contrary, it’s strongly advised against! However, what causes prolactin levels to rise in breastfeeding people works the same way in non-breastfeeding people—and once again has the potentially unwanted effect of reducing fertility in both the person who may become pregnant and the person who may father the child.
Diet also has an impact
Prolactin has many different mechanisms of action in both the female and male body—too many to cover in detail. However, we think it’s worth mentioning that diet also plays an important role in regulating hormonal balance. For example, one study has shown that improvements in erectile function and vascular health after switching to a plant-based Mediterranean diet rich in fiber, secondary plant compounds, and unsaturated fatty acids, and low in animal-derived nutrients, are directly linked to reduced prolactin levels.
Prolactin and overweight
It has also been shown that elevated prolactin levels are often associated with being overweight. The duration of hyperprolactinemia was particularly important here. In animal studies, a long-term increase led to increased food intake and a subsequent rise in body weight, and had a negative effect on the glucose tolerance and insulin sensitivity of body cells.