Prolactin; a Hormone with Many Functions

I recently got lost in studies on prolactin. I was enlightened at what all this hormone has, as a job. A busy hormone, for sure! I thought I’d share my findings. 
 
 
Most know that Prolactin is a major hormone in breast milk reproduction. Outside of breast milk production, what is prolactin’s role, though? Did you know it has roles outside of breast milk production?  
 
Here are a few functions one might not be aware of: 
 
Prolactin receptors are present in the preimplantation embryo, so before the embryo even implants in the uterus, prolactin already has its own thing going on. (2) 
 
A lack of endometrial prolactin during the implantation window has been linked in study, to those affected by unexplained infertility and repeated miscarriages. (5) 
 
Prolactin is a care-giving hormone in mammalian biological parents, promoting maternal adaptations. Outside of reproduction, it is a stress and growth hormone – makes sense! (4) 
 
In early pregnancy, the increase of prolactin in the mother may offer stress-reducing effects that also benefit the baby in utero. (4) 
 
Disruption of the prolactin receptor during embryonic development can induce a range of developmental defects. Proven in study of zebra fish; lack of prolactin caused multiple morphological defects. (1) 
 
Near term, prolactin increases in the uterine lining, otherwise known as the “decidua”. The Decidua is the thick layer of modified mucous membrane which lines the uterus during pregnancy, and is shed with the afterbirth. Studies show that this prolactin function may be involved in labor processes. (4) 
  
This one was mind blowing for me —-> PROLACTIN IS IN OUR AMNIOTIC FLUID. Who knew? Its function makes perfect sense, too! The prolactin (growth hormone) filled waters fill the baby’s lungs in utero. Studies suggest that this may assist with respiratory preparation, getting the lungs ready for life earth side – again, makes sense! (4) 
 
Baby’s prolactin production also increases close to the onset of spontaneous labor. Studies suggest this may promote the transitions baby will endure postpartum. (4) 
 
Prolactin receptors are essential for odor detection, facial sensation, taste, and the neonatal suckling reflex. Prolactin receptors can be found in the fetal trigeminal ganglion (sensory nerve involved in infant suckling), tongue, whisker follicles (for animals), and facial musculature. This is how infants know to find the breast after birth and to suckle! (1) 
 
Checkout how your birth location, and the way you are treated in labor can impact postpartum! – Makes a whole bunch of sense, doesn’t it?! 
 
“High-quality research is lacking in relation to possible impacts of maternity care practices on prolactin physiology. Stress in labor may paradoxically reduce prolactin secretion, givinginfraphysiologic levels in labor and birth, possibly contributing to the negative impacts of labor stress on breastfeeding. Epidurals may cause in-labor prolactin elevations and postpartum prolactin reductions, with unknown impacts. Induction with synthetic oxytocin may also impact physiologic prolactin release. Prostaglandins may inhibit prolactin with possible impacts on breastfeeding success. 
With cesarean section, the expectant mother may miss her pre-labor prolactin elevation, late-labor peak and/or postpartum elevations, which may all impact milk production and maternal adaptations. Following cesarean section, prolactin release with early breastfeeding may be reduced or absent. These and other factors may contribute to reduced breastfeeding success following prelabor cesarean section. Following cesarean section, newborns may have lower prolactin levels, possibly contributing to breathing difficulties and low temperature. Lack of the catecholamine surge may also contribute. 
Separation of mothers and their healthy newborns, which typically follows cesarean section, may also impact postpartum maternal prolactin levels. If separation interferes with early breastfeeding initiation and frequency, disruption to prolactin receptor formation may impact ongoing milk production and breastfeeding success.” (4) 
 
There are many more functions of prolactin and prolactin receptors, I’m sure. If you’d like to learn more, there are plenty of studies on this hormone! Information shared in this post was gathered from the links below. Be careful, you might get stuck in amazement once you start digging!  
 
1. https://www.sciencedirect.com/science/article/pii/B9780123971753000120 
2. https://www.ncbi.nlm.nih.gov/pubmed/15820039 
3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5941656/ 
4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4720867/ 
5. https://www.ncbi.nlm.nih.gov/pubmed/15218000 
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