What is the Function of Prolactin in the Male1

8/3/2019 What is the Function of Prolactin in the Male1

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Topic: What is the function of prolactin in the male?

Prolactin is a hormone primarily produced by the anterior pituitary whose

secretion is regulated by neurons in the hypothalamus. Its documented function in

females is to act upon the breast, a nonendocrine target, and stimulate the development of

the mamillary glands, synthesize milk production, and regulate milk secretion3. Even

though the main function of prolactin has been associated with lactation (hence the name),

recent research has begun to shine light on its various properties and functions that

suggest the hormone is involved in a myriad number of biological processes ranging from

reproduction to physiological homeostasis. Prolactin, for example, has been found to be

secreted by tissues other than the anterior pituitary gland such as the uterus and the

epithelial cells of the mammary gland 3. Similarly, prolactin receptors have been found

to be located on a myriad of organs and tissues (such as the ovaries, heart, liver, and

skeletal muscle tissue) other than the mamillary glands, with which it is commonly

associated 3.

The role of prolactin in males is of particular research interest since little is known

about its function. The available research on humans and model organism suggests,

however, that it may play a role in the function of the testis and reproductive organs,

seasonal breeding cycles, and sexual satiation. A study conducted on hypophysectomized

(the surgical removal of the pituitary gland) male mice for instance linked administered

prolactin with an increase in spermatogenesis yield5

while a study conducted on

hamsters with induced gonadal atrophy found that those treated with prolactin had higher

levels of plasma testosterone and higher testes weight compared to the controls7

. It is


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thought that prolactins interaction with neurotransmitters in the hypothalamus and its

influence on androgen receptors in the pituitary results in a decreased sensitivity of

gonadotropin release to testosterones negative feedback, and can thus play a role in the

regulation of seasonal breeding in male species4.

In human males, studies have shown that prolactin may have some role as a

feedback regulator of the refractory period following an orgasm. A study published in

2002, for example, found increased levels of plasma prolactin following orgasm in

healthy male subjects (whose refractory periods were on average 19 minutes) while no

prolactin response was detected in the case subject (whose refractory period was on

average 3 minutes)2. Moreover in a similar study of male subjects where prolactin levels

were pharmacologically increased, small reductions in sexual parameters (such as drive,

arousal, orgasm and refractory period) were noticed while a decrease in prolactin resulted

in an increase in sexual parameters5. This suggests that prolactin may also play a role in

modulating the CNS, thereby affecting sexual behavior and libido5.

Lastly, it is interesting to note that high levels of prolactin in men inhibit the

release of gonadotropin-releasing hormone and thus FSH and LH, resulting in

hypogonadism. This illness is characterized by low blood testosterone levels, a decrease

in sex drive, and a decrease in other sexual functions.

In conclusion, though there is still much to learn concerning prolactin and its

function in the male, it does act as a progonadal hormone that promotes testicular and

reproductive function in addition to having a role in sexual satiation.


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References

1.http://www.medical.siemens.com/siemens/en_GLOBAL/gg_diag_FBAs/files/referenz

werte_pdf/IMMULITE_Systeme/prolaktin.pdf

2. http://www.nature.com/ijir/journal/v14/n2/full/3900823a.html

3. http://www.med.umich.edu/1libr/aha/umneuro_prolactinoma.htm

4. http://www.andrologyjournal.org/cgi/content/full/25/5/661

5. http://joe.endocrinology-journals.org/cgi/content/abstract/49/2/311?ijkey=7644f13407162ae0323a45d4f0c449c4e

1983ce8&keytype2=tf_ipsecsha

6. http://molehr.oxfordjournals.org/content/8/7/606.full#ref-2

7. http://www.ncbi.nlm.nih.gov/pubmed/1204580

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What is the Function of Prolactin in the Male1