Prolactin in Men, Part 1: Overview and discussion of hypoprolactinemia (low prolactin levels)

There are downsides of having too low of prolactin levels in men

Prolactin is a hormone produced by the anterior pituitary that is best known for its effects on lactation (production of breast milk) and the development of breast tissue, although it has a wider range of effects.

The primary source of prolactin is the anterior pituitary, but it is also be produced peripherally in the central nervous system, the immune system, and the mammary glands.

It is possible that prolactin is a requirement for human life — this is suggested by the fact that there is no known genetic knockout of the prolactin or prolactin receptor genes in humans.

Prolactin provides the body with a feeling of satisfaction and relaxation after sexual acts, commonly referred to as the refractory period, by dampening the pathways that are activated by dopamine during sexual activity.

When prolactin levels are in the normal range, it has direct effects in the testes, enhancing LH binding to LH receptors which results in higher testosterone, and it is also involved in promoting spermatogenesis. In the CNS, prolactin has neuroprotective effects and helps deal with stress and anxiety. It also has effects related to fluid and electrolyte balance, body growth, lipid and carbohydrate metabolism, and the immune system.

Feedback control of prolactin

The graphic below gives a great overview of the feedback loop used to control prolactin release.

Image source: https://www.mdpi.com/1422-0067/22/20/11247

A few notes:

• The main way that prolactin is controlled is by inhibition of its release, primarily by acting the action of dopamine acting on D2 receptors. (Since viewing pornography results in extremely high and sustained dopamine levels, this results in low prolactin levels, which we’ll be discussing next). GABA plays a minor role.

• The strongest stimulus for prolactin is suckling and nipple stimulation.

• Other things that stimulate prolactin include: