Prolactin

Prolactin is a hormone secreted by the pituitary gland during pregnancy and stress, which promotes milk production, removes calcium from the bones, and inhibits progesterone formation 4. Prolactin acts on the thyroid gland to decrease its activity and on other tissues to increase their glycolysis, while decreasing oxidative metabolism 4.

Prolactin has been shown to induce nitric oxide synthase in rat C6 glioma cells, leading to an increase in nitric oxide release and expression of inducible nitric oxide synthase 1. This effect is concentration-dependent and can be inhibited by dexamethasone, an inhibitor of de novo iNOS synthesis 1.

Research has also shown that prolactin receptors are present in patients with meningiomas and schwannomas, and that high levels of prolactin are associated with these tumors 3. Furthermore, studies have demonstrated that prolactin promotes apoptosis-driven hair follicle regression and is implicated in the pathogenesis of androgenetic alopecia 7.

Prolactin has been found to be expressed in murine hair follicle epithelium and to induce catagen development in vitro 5. Additionally, human scalp hair follicles are both a target and a source of prolactin, which serves as an autocrine and/or paracrine promoter of apoptosis-driven hair follicle regression 7.

The mechanism of prolactin action involves increased intracellular concentration of potassium and reduced level of sodium, increased level of cGMP and reduced level of cAMP, enhanced rate of prostaglandin biosynthesis, and stimulation of polyamine synthesis 7.

In the context of prostate cancer, concurrent with DLP dysplasia induction, a dual hormone regimen elicits hyperprolactinemia, which is associated with marked epithelial cell proliferation in the dysplastic foci 8.