I am using a prolactin inhibitor drug called "Dostinex". In general, it has some positive effects on me (increased libido, better mood) and I haven't realized any bad side effects. I'm wondering, which systems in the body can be affected negatively by low prolactin levels?
Prolactin is a peptide hormone that, in addition to modulating the hypothalamic–pituitary–gonadal axis, functions as a cytokine in the immune system and as a growth factor in the vascular system amongst many other functions.
According to Wikipedia:
Prolactin receptors are present in the mammillary glands, ovaries, pituitary glands, heart, lung, thymus, spleen, liver, pancreas, kidney, adrenal gland, uterus, skeletal muscle, skin and areas of the central nervous system.
How prolactin suppresses GnRH, the mechanism through which hyperprolactinemia causes hypogonadism, is unknown. Many of prolactin's other functions may not necessarily be influenced by blood serum levels, as prolactin acts in a paracrine and autocrine, in addition to an endocrine, manner.
The positive outcomes from normalizing hypogonadism should outweigh any negative effects of reducing prolactin levels. Androgen deficiency in males can cause osteoporosis, a series weakening of the bones. Of course, as more is known about the function of elevated prolactin levels, this opinion may change.
Surprisingly, serum prolactin below physiological levels can cause many of the symptoms that high levels can. Prolactin acts as a weak gonadotropin by itself, and enhances the effect of leuteinizing hormone at testosterone-producing cells in males.
Hypoprolactinemia can lead to hypogonadism and osteoporosis, just like in hyperprolactinemia. However, in cases of hyperprolactinemia, cabergoline often does not completely reduce prolactin to normal levels, anyway.
The side effects of cabergoline itself are probably more important. as there are known cases of valvular heart disease in doses used to treat Parkinson's. Inflammation and fibrosis of various tissues can also occur.