in the hypothalamus and transported to the pituitary lactotrophs where DA (dopamine) binds to D2 receptors in order to inhibit the release of PRL (Ben-Jonathan, 1985). The most likely mechanism for the release of prolactin is disinhibition of dopamine. When dopamine releases its inhibitory affect on the hypothalamus it frees the pituitary gland to release prolactin. It has been found that mice with a disrupted D2 receptor gene have an overproduction of prolactin and leading to lactotroph adenoma. Although the inhibitory influence of dopamine on prolactin is almost certain, the inverse relationship is not always present. “This inconsistency between dopaminergic activity and prolactin secretion could be easily resolved by assuming that additional PIF may also contribute to the negative control of prolactin secretion (Mark E. Freeman, 2000). This suggests that there might also be other inhibitors that regulate its release. Some researchers believe that among them could be GABA and somastatin. Finally, prolactin secretion could also be influenced by the lactrotrophs and by other cells within the pituitary gland.

6. What is the effect on the organism if this hormone is over/underproduced?

Prolactin deficiency is caused when one has a general shortage of the pituitary hormones. Deficiency can cause Sheehan syndrome, in which the pituitary gland is destroyed during or shortly after giving birth. Additionally, a decrease in prolactin can cause a mother to produce insufficient milk. People who are found to have low prolactin levels are also expected to be more susceptible to some infections. Increased prolactin secretion can be caused by damage to the pituitary stalk. This causes prolactin to be less regulated because it blocks the flow of dopamine from the hypothalamus to the lactotrophs. An increase of prolactin can also be caused by the development of Pituitary hormone-secreting tumors. The prolactin secreting tumors are called prolactionomas, and cause abnormal lactation (galactorrhea), menstrual abnormalities, and infertility. Additionally, for women of reproductive age, a surplus of prolacin can cause decreased secretion of gonadotropins which means a decreased cyclis ovarian function. This can cause women to experience loss of sexual desire, dryness of the vagina, infertility and sometimes galactorrhea (abnormal lactation). For men, a high concentration of prolactin can decrease testicular function causing loss of sexual desire, erectile dysfunction, muscle weakness, and infertility.