User:Charlene.est.33/My sandbox

Draft: Endocrinology of Parenting

Nonhuman females[edit]

Many nonhuman studies can be used as both potential models for humans and to show the phylogenetic conservation of some endocrine signals.[1] Estrogen and progesterone released by ovaries during pregnancy make oxytocin receptors more sensitive in female rats[7] and is associated with the onset of maternal behaviors in other species as well.[3][8][9] Maestripieri found a very similar relationship, whereas estrogen and progesterone are increased during pregnancy and oxytocin was increased postpartum (slightly confusing wording: ) .[10] Estrogen, progesterone, and estradiol in pregnant mammals, in some species, but not all, correlate with maternal behavior before the birth of their offspring, with other infants, and after with their own infants.(appear to be awkward wording: The presence of estrogen, progesterone, and estradiol in pregnant mammals in some species appears to exhibit a correlation to maternal behavior in the mammals before and after the birth of their offspring as well as in interactions with other offspring/infants.) [3]

However, an increase in hormones influences maternal behavior, but it is not always the cause of the onset of maternal behavior in females. Some studies on primates in which increased estrogen and progesterone have a negative or no (absent?) correlation with maternal responsivity are in black tufted-ear marmosets,[11] common marmosets,[12] lowland gorillas,[13] and baboons.[14] However an experimental study on nulliparous rats, who tend to avoid pups, found that when they were transfused with postpartum rat's blood, which is high in estrogen and progesterone approached the pups in response to their cues. (reword to say: Alternatively, however, one experimental study showed that nulliparous rats, which tend to avoid pups, were transfused with postpartum rat blood that is high in estrogen and progesterone, resulting in their responsiveness to the pups’ cues) [15] Because of this variation between species, the effects of the hormones listed does not give much weight to the phylogenetic conservation of these neuroendocrine mechanisms; although Saltzman points out that the social structure of some species may be significant.[3] Previous exposure to infants, in social species, rely (relies) less on these hormones to activate mechanisms and more on modulating maternal behavior because parenting behaviors are not always dependent on hormones.[3]

On the other hand, in non-human primates specifically, lactating females of multiple species exhibit an alarming correlation with increased estrogen, and (omit this) progesterone, and prolactin.[3] These species include black tufted-ear marmosets,[11] baboons,[14] rhesus macaques,[16] and gorillas.[13] Endogenous signals, like increasing estrogen compared to progesterone, increases the amount of prolactin, the “lactation hormone,” in the bloodstream, as well as exogenous cues from infants, like suckling. (reword: Endogenous signals such as an increase in estrogen compared to a decrease in progesterone, causes an increase in the levels of prolactin, the “lactating hormone,” in the bloodstream. Furthermore, exogenous cues from infants such as suckling induces this mechanism.) [17] Oxytocin, has been found to play a key factor in breastfeeding and increase similarly to prolactin, with increases in estrogen and infant cues. (reword: The hormone oxytocin, similarly to prolactin, has been found to increase with an increase in estrogen and the presence of infant cues such as suckling/breastfeeding.)

Suckling also increases oxytocin levels in rhesus macaques (this fact appears to be misplaced) ,[10] and oxytocin has also been found in other non-human species to inhibit the rejection of offspring;[3] oxytocin is essential for responsive and sensitive caregiving.[19][20][3][21] Some specific examples include Francis' study on female rats which linked a high amount of oxytocin receptors to increased (omit this) an increase in acts grooming,[22] and another study by Maestripieri which linked (an increase in) oxytocin levels in free-ranging macaques to increased nursing and grooming. (to an increased tendency to nurse and groom.) [10] However, experimental results are less conclusive. (As aforementioned,) (omit) N(n)ulliparous mice do not respond to pup calls, but when administered with oxytocin they do.[23] A similar study conducted by Holmon and Goy tested nulliparous rhesus females, where (their behavior) post injection did not elicit a drastic response to infants, however there was a notable change in the adult's behavior, including increased proximity and touching. (however, a notable change within the adults presented an increase in proximity and touching). [24] Oxytocin is more often described as a hormone that facilitates bonding and not one that directly increases care.[25][24][26][10] Also, the mice were responding to pup calls and the rhesus macaque infants weren't necessarily providing cues. (this sentence appears to contradict the second sentence, perhaps clarify?) Similar to the explanation provided for the variation in estrogen and progesterone, rhesus macaques live in drastically different environments. (expand upon the explanation and how it affects the variation in behavior?- it just sounds confusing) Saltzman proposes that this is due to primates living socially and having a slower developmental trajectory, in which learning is more important. (this appears to be out of place) [3]

Human females[edit]

Like in many nonhumnan (nonhuman) animals, human mothers go through a period of high progesterone during pregnancy that is followed by a decrease in progesterone and a subsequent increase in estrogen, prolactin, and oxytocin (near the end of their pregnancy). During pregnancy and postpartum, a high estradiol to progesterone ratio is associated with mother(s) reported (reporting) higher feelings of attachment.[27] High levels of progesterone, which is(are) associated with pregnancy, inhibits prolactin and therefore lactation.[28] Prolactin increases during the initial stages of lactation and can be stimulated by infant cues and estrogen, but not progesterone and infant cues (omit). [28] Research (,however,) focuses on the role of prolactin for breastfeeding and less on other behaviors.[28] Prolactin increases with infant suckling but not other forms of infant contact.[29] Oxytocin, on the other hand, increases with both suckling, and physical contact in human females.[28]

Oxytocin in human females is associated with the level of physical affection and bonding. (Oxytocin levels in human females are associated with the presence of physical affection and bonding) Feldman (2010) found that mothers who displayed “high affectionate contact” had increased oxytocin levels post interaction, but not mothers who displayed “low affectionate contact.”[21] Oxytocin is believed to provide a feedback loop, meaning that maternal-infant contact increases oxytocin and oxytocin increases maternal behavior and facilitates bonding.[30] In one study oxytocin also played a role on mother reported attachment to her fetus.[31] Nonhuman males[edit]

Wynne-Edwards and Timonin recognize that paternal care is not primed in the same way as females (maternal care) simply because they do not go through pregnancy. Therefore, males do not go through the same hormonal changes as women.[32] The simplest way, through natural selection, for paternal care to evolve or be maintained is to use the same or similar pathways as females.[33] Wynne and Reburn (2001) suggest that fathers who are pair bonded and spend time with the soon to be mother may activate paternal pathways through various cues.[33] Estradiol increases just before their offspring's birth in black-tufted-ear marmosets and dwarf hamsters and possibly activates certain pathways involved in paternal behavior.[34][35] This is similar to estrogen and progesterone in pregnant females. However, the manipulation of estradiol does not increase or decrease paternal behaviors.[32] This may be similar to the finding that women who do not breastfeed or do not have vaginal births still respond to their infants.[19]

Like expecting and new mothers, fathers in multiple mammals have elevated prolactin levels compared to non-fathers. These species include California mice,[36] Mongolian gerbils,[37] dwarf hamsters[disambiguation needed],[38] meerkats,[39] marmosets,[40] and cotton-top tamarins.[41] However, the previously listed studies have different cues and are associated with different paternal behaviors and (this)- omit) may be due to species specific mechanisms or simply different contexts. The above species are biparental and the elevated prolactin levels in males were not exclusive to fathers.

There are variable results between males of different species as to the effects of oxytocin on paternal care. (…between the effects of oxytocin on paternal care between males of different species). Oxytocin (levels are) is unchanged in California mice before and after becoming fathers,[42] but the amount of paternal exposure to rats is associated with (an increase in) oxytocin and increased care.[41] However, multiple studies on biparental species show an association between paternal care and oxytocin.[42][43][33][44] Since the species in these studies are biparental, excluding rats, it is unclear as to why California mice do not have a change in oxytocin postpartum.

Human males[edit]

In human mothers, oxytocin is associated with high physical contact and affection. However, studies on fathers show that oxytocin is related to high stimulatory contact and exploratory play.[21][45] This supports three hypotheses: 1.	Mothers and fathers play different roles.[6] 2.	Mothers and fathers have similar pathways.[32] 3.	That there are parallels to animal models,[21] assuming that a high amount of OT receptors in nonhuman animals is associated with a high amount of oxytocin

Comparison of estrogen, progesterone, prolactin, and oxytocin between species and sex[edit] Across multiple species and in some cases across sexes, there is evidence for the phylogenetic conservation of parental hormones. These include the relationships between the hormones estrogen, progesterone, prolactin, and oxytocin. In both non-human primates and humans, the increase in estrogen and progesterone during pregnancy is often followed by a decrease in progesterone and an increase in prolactin, postpartum.[11][14][13][24][28] In males across species, including humans, increased prolactin levels are associated with fatherhood.[36][37][38][39][40][41][46][47]

In some studies on females across species, estrogen and progesterone prepartum is also related to oxytocin.[7][3][8][9][10] Although, the relationships between these hormones is similar across species, there is variation in the degree to how oxytocin effects behavior. For example, in some species, like rats, an increase in oxytocin greatly increases interactions with infants,[23] but an increase in oxytocin in macaques only mildly increased interactions.[24] However, the importance here is that oxytocin increased interactions in all of the relevant cited studies for females,[7][3][8][9][24] as well as the majority of studies cited for males.[42][43][33][44] In fathers across species the effects of oxytocin are more variable, however in general oxytocin is associated with increased paternal care.[42][43][33][44] In human fathers increased oxytocin is linked to increased involvement, however the type of involvement is different between fathers and mothers, where fathers focus more on stimulatory contact and exploratory play.[21][45] In human mothers oxytocin is associated with general care and affection.[21]