Produced mainly by the pituitary gland, this hormone kicks into high gear during pregnancy to facilitate the production of breast milk. But lactation is just one of this hormone’s many roles. While prolactin levels stay relatively low during other stages of life, it is produced in several sites throughout the body, including the skin, and it is involved in both the skin’s immune system response and the system known as the “brain-skin axis.” Prolactin is one of the hormones released in response to stress and it is connected to skin and hair diseases like psoriasis and alopecia.