According to the Society for Endocrinology, low levels of prolactin mean that a person has hypoprolactinaemia, which can lead to low breastmilk production and possibly to a weaker immune system. However, most people with this rare condition do not have medical problems as a result.
The Society for Endocrinology states that low prolactin levels normally result from underactivity of the pituitary gland. Prolactin is responsible for metabolic and reproductive functions, as well as the regulation of fluids and the immune system. The two main regulators of the production of prolactin by the pituitary gland are dopamine and estrogen. Dopamine, which is produced by the hypothalamus, inhibits the production of prolactin. Therefore, a high level of dopamine leads to low levels of prolactin secreted.
On the other hand, the Society for Endocrinology notes that estrogen increases the production of prolactin. Studies show that more prolactin is present in the blood during times when estrogen levels are high. Thyrotropin-releasing hormones, anti-diuretic hormones and oxytocin can also increase or decrease the levels of prolactin.
The opposite of hypoprolactinaemia is hyperprolactinaemia, which is the condition in which too much prolactin is in the blood. This condition can cause menstrual cycle disturbances and unwanted breastmilk production in females, and it can lead to testosterone deficiency in males.